Exhibit 2001 CBM2016-00083 SR-IS V.002275 BOC Notes on the LEC Networks 1994 Issue April1994 Contents
BOC Notes on the LEC Networks Contents
Foreword xi
Overview 1-1
Local Access and Transport Areas 2-1
2.1 LATA Design Requirements 2-1
2.2 Design Exceptions 2-3
2.3 BOC Relationship with Other ExchangeCompanies 2-4 2.4 BOC Offshore International and Independent LATA Assignments 2-4
Numbering Plan and Dialing Procedures 3-1 3.1 NANP Number Structure 3-2
3.2 Numbering Plan Areas 3-2 3.3 Service Access Codes 3-6
3.4 Nil Service Codes 3-8
3.5 Central Office Codes 3-8
3.6 Implementing Interchangeable Codes 3-12
3.7 Telephone Numbers 3-16
3.8 Dialing Procedures 3-17 3-19 3.9 Dialing Prefixes for CarrierSelection
3.10 Operator Assistance .3-20 3.11 International Direct Distance Thahn 3-20 3.12 OXX and lxx Codes 3-21
3.13 Special Characters and 3-22 3.14 Vertical Service Codes 3-23
3.15 SS7 Point Codes 3-23
3.16 Automatic Number Identification II Digit Assignments 3-24
Network Design and Configuration 4-i 4.1 Introduction 4-1
4.2 Operator Services Systems 4-10 4-17 4.3 Network Design Considerations
4.4 Blocking Probabilities 4-24
4.5 LATA Network Configurations 4-25 4-43 4.6 Reliability of Equipment and Systems 4.7 Network Service Evaluation 4-54
Billing Customer Data and Control 5-1
5.1 Automatic Message Accounting 5-1 5.2 Network Service Evaluation 5-7
5.3 Customer Network Services 5-8
5.4 Customer Network Management 5-10 BOC Notes on the LEC Networks 1994 SR-TSV002275 Contents 4iue AprIl 1994
Signaling 61 6-1
.2 Access Line Signaling 6.12 6-30 Interoffice Signaling 6-33 64 On- and Off-Hook Signals 6-44 65 Controlled Outpulsing 6-59 66 DialPulsing 6-70 67 Loop Signaling EMSignaling 6-74 692 69 Duplex Signaling System
10 EM Signaling for Customer Insthllatlon Equipment 611 AC Supervisory and Addressing Systems 6-94
12 Mtitifrequency Pulsing 6412
13 Dual-Tone Multifrequency Signaling 119 6-133 614 Calling Number Delivery .. 615 LATA Access 6-136 -6-17 16 Special Tandem Signaling CAMA OSPS and TOPS Offices 6-180 617 Operator-Services Office Coin Control Signaling 18 Operator-Services Office Signaling Sequences for AutomáticCáinTollServiceandCallingCardService 6-184 6-203 6.19 Operor-Services.Miscellanèous Services 6-209 620 Signaling to Automatic Intercept System 6-210 621 Camer Group Alarm 6-214 622 Call Progress Tones Audible Tone Signals 6-228 623 Othet Miscellaneous Signals 6-255 6.24 Regitr Timinga id Effecto Signaling 625 Commop Channel Signaling 6-255
Transmission 7-1 Introduchon 7-1
72 Network Arclutecture 7-1 7-3 Objectives ad Limits 74 Voice Tranmission Impairments and their Control 7-5
75 Voiceband Data Transmission Impairments and 7-17 theirCojitrol 7-21 76 bigital Transmission 7-3 77 Digital Data Transmission
LTransmission Aspects of Switches 7-27 7-30 79 Adaptive Ilfferential Pulse-Code Modulation Technology 7-31 10 4ynchronous Transfer Mode Technology 11 Ento-End Performance 7-36 7-43 7.12 Network Transmission Design 7-57 13 Operator Services Transmission 14 Transmission Lmuts intraLATA Networks 7-61 7-67 15 Loop Transmission Design and Charactenzation
vi SR-TSV-002275 BOC Notes on the LEC Networks 1994 Contents Issue AprIl 1994
7-74 7.16 Interoperation with Other Networks
Operations and Maintenance 8-1
8.1 Introduction 8-1
8.2 TrunkMaintenance 8-2
8.3 Comwon Channel Signaling 8-29
84 Switch Diagnostics 8-41
8.5 Switching System Maintenance 8-50 8.6 Memory Adñiinistration 8-52
87 Facility Maintenance 8-53
8.8 Transport System Maintenance 8-55 89 Loop Maintenance 8-60 8.10 Planned Long-Term Network Advancement 8-62 8-65 811 Digital Testing Parameters
Common Systems 9-1
9.1 Introduction 9-1
92 Cross-Connect Systems 9-1
93 Power Systems 9-10
94 Network Equipment-Building System 9-17
.Vc 10 Surveillance and Control 10-1
10.1 Network Traffic Mangement 10-2 10.2 Network Service Center 10-36 10.3 Servce Evaluation Center 10-44
11 Synchronizati 11-1
1.1 Introduction 11-1
11 Synchronization Background 11-1 11.3 Hierarchièal Method of Synchronizati 11-3
11.4 Internodal Synchromzati 114. .11-9 1-1.5 Intranodal Synchromzati 11-10 11.6 Reliability and Performance
11.7 Interconnection with Other Networks 11-13 11-13 11 Plesiochronous Operation 11 Mminitration 11-13 1110 Synchronization Network Operations 11-14 11-16 1111 Synchronization Network Testmg
12 Distribution 12-1
12-1 12.1 Introduction 12-5 12.2 Metallic Loop Conditioning 12-7 123 BOC Loop Surveys 12-18 .1 2.4 Voice-Frequency Channel Terminating Equipmát 12-18 12.5 Analog Lc$op Carrier
vii BOC Notes on the LEC Networks 1994 SR-TSV-002275
Contents Issue April 1994
12-18 12.6 Universal Digital Loop Carrier 12-23 12.7 Integrated Digital Loop Carrier 12.8 Basic ExchangeRdio System 12-27 12.9 ISDN Distribution Transport 12-30
12.10 Universal Digital Channel 12-39
12.11 Distribution Network Physical Structures 12-41
12.12 New Technology 12-43
13 Terminal Equipment and Premises Wiring Interconnection 13-1
13 Introduction 13-1
132 Scope 13-2 133 Terminal Equipment Connections 13-6
134 Grandfather Requirements 13-10
13 Interface Specifications 13-12 136 Incidence of Harm 13-14
137 Compatibility Reqwrements 13-17 13-17 13 Testing and Maintenance
14 Network Architectures and Services 14.-i
141 Introduction 14-1
14.2 Common Channel Signaling 14.3 CLASS Services .14-13 14.4 Service Enabling Technologies
Simplifying the User Interface 14-21
14.5 Alternate Billing Service i4-27 14.6 800 Data Base Service 14-34
14.7 Advanced Intelligent Network 14-51
14.8 Integrated Service Control Point 14-57
14.9 Integrated Services Digital Network .. 14-76
14.10 Public Switched Digital Service
14.11 Public Packet Switched Service 14-99
14.12 Asynchronous..Trawfer Mode-based
Broadband Integrated Services Digital Network 14-114
14.13 Frame Relay 14425
14.14 Switched Multi-megabit Data Service 14-130
14.15 Synchronous Optical Network 14-135
15 Exchange Access 15-1
15.1 PointsofPreseuce 15-1
15.2 Expanded Interconnection 15-1
15.3 Switched-Access Service 15-2
15.4 Special-Access Service 15-5
15.5 Other Network Services 15-9
15.6 Interconnecting Entities 15-11
15.7 Transmission 15-12
viii SR-TSV-002275 BOC Notes on the LEC Networks 1994 Contents Issue April 1994
15.8 Signaling 15-12
15.9 Automatic Message Accourting Measurement
Requirements 15-12
16 Mobile Services Interconnection 16-1
16.1 Wireless Services Providers 16-1
16.2 Interconnection Types 16-3
16.3 Optional 1eatures 16-31
16.4 Conventional 2-Way Mobile Service 16-32
16.5 Land-to-Mobile Calls 16-35
16.6 Transmission and SignalingRequirements 16-36
16.7 Common-CarrierPaging Ssthms 16-38
16.8 FCC Part 90 Private Carriers.. 16-42
16.9 CT2 Concept 16-43
16.10 Personal Communications Services 16-43
17 Open Network Architecture 17-1 17.1 Common ONA Model 17-1
17.2 Basic Serving Arrangement Categories 17-3
17.3 Regulatory Background 17-23
18 National Industry Forums and Standards Committees 18-1 18-1 18.1 Affiance for Telecommunications Industry Solutions
Glossary G-1
Abbreviations ...... G-1
Acronyms G-3
Definitions
Symbols G-52
Index Index-i
Ix BOC Note on the LEC Networks 1994 SR-TSV-002275
Contents lesue April 1994
SR-TSV-002275 BOC Notes on the LEC Networks 1994 Foreword Issue April 1994
Foreword
BOC Notes on the LEC Networks 1994 Issue replaces all previous issues The
reflect than four of subjects discussed in this document more years technological progress
and change in the Local Exchange Carrier LEC networks Regulatory rulings judicial
decisions standards activities and forum bodies have contributed to the changes
its view of technical Notes is Special Report published by Belicore to provide topics
It is related to typical LEC switched network characteristics not generic requirements
the constitutes or on the of document No part of text suggests requirement part any
LEC or other entity Attempts have been made to ensure that information contained
herein is recent and reliable However due to the constant evolution in technology and
available its associated documentation you should seek the most current information the various regarding topics of interest Requirements and specifications for components in Beilcore that constitute LEC networks are generally contained generic requirements Generic or Technical References or publications usually Requirements
standards documents where actual requirements are clearly identified and described To
and functions of various of the adequately explain the technical attributes operating parts refer manufacturers networks it has been necessary in some cases to to specific
equipment or systems presently in widespread use These references do not constitute
recommendation of the specific equipment or their manufacturers by the LECs or by
Beilcore Throughout the document numerous references are made to act as source for
additional information on the topics presented
and communications Notes is narrative discourse on the technical aspects of services market-area switched paths through the intraLATA Local Access and Transport Area or
networks to their boundaries It contains technical material of interest to engineering and
planning groups as well as descriptions of the characteristics and background of these This issue of Notes overview of some of the subjects in laymans terms provides an characteristics and basic of switched-access and typical technical operating principles and network services that have become transport networks New technologies systems
available since the 1990 issue and that are availableand commonly deployed as of year-
end 1993 have been included Interconnection arrangements between the LECs and other networks also covered entities that currently exist in some or all of the LEC switched are covered in Experimental local-application or individual-case base arrangements are not
this document
Readers familiar with previous issues of Notes will find new sections as well as changes
in format and content designed to make the material useful regardless of the readers
technical background Changes to the placement of text were minimized because many readers have become familiar with the way this document has been arranged subject- concludes each section Section of this specific list of references and bibliographies further detail In document Overview explains text organization and content in addition
an Index has been added to the document to provide easier access to particular subject
referred in consistent with To ensure that telecommunications entities are to manner of terms legal regulatory and industry conventions it is necessary to use variety and These follows acronyms to differentiate between types of LECs are explained as
xl SA-T8V002275 BOC Notes on the LEC Networks 1994 Foreword Issue AprIl 1994
LEC Local Exchange Carrier refers to any and all exchange carriers
that provide telecommunications exchange and exchange-access service
of the BOC Bell Operating Company refers to LEC that was part former Bell System
Independent LEC Independent Local Exchange Carrier refers to LEC that was Bell not part of the former System
transmission All LEC switched networks are composed of integrated parts that consist of and associated and switching systems control and signaling processes operational each LEC support systems that are engineered owned and managed by independently With these networks the LECs provide administer and maintain telecommunication services and offer facilities arrangements to other entities that also provide telecommunication services
function is on-demand Two primary functions are provided by these networks One an of termination within the communication path to connect any two customers points LATA or market area The other function is to connect these points of termination to the point of termination of another entity providing telecommunication services to its end users for the purpose of exchanging information
Each LEC has an individual business plan that guides its deployment and operations LEC activities so many of the characteristics described may not apply to particular and affect individual network These plans vary greatly between companies obviously company purchasing and deployment decisions Current network technology permits These from LEC LECs to offer wide variety of service offerings offerings vary widely be to LEC and at times within particular LEC virtually identical service may offered by several LECs under different names prices and/or arrangements Availability the and compatibility information changes almost daily The serving LEC has most
about its individual current detailed and specific information offerings deployment status and specifications
the Joint p1nning between the LECs wherever practical and appropriate contributes to To such the provisioning of least-cost telecommunication services encourage efforts information contained in this issue reflects consultation and review by subject-matter
the United States experts of the regional companies the BOCs Beilcore Telephone and the Association USTA the National Telephone Cooperative Association NTCA Organization for the Protection and Advancement of Small Telephone Companies OPASTCO
and other Individual differences between LECs the effects of state regulatory bodies Notes factors aie beyond the scope and technical focus of this issue does however furnish much of the information needed by the telecommunications industry regulators This consultants and vendors to maintain and/or interact with the LEC networks
xli the LEC Networks 1994 SRTSV002275 BOC Notes on Foreword Issue April 1994
technical document although broad in scope cannot cover all of the detailed Contact LEC characteristics of each LEC continually evolving switched network your
service Both Beilcore and the individual for detailed information specific to your area LECs may also have more detailed material available
xii BOC Notes on the LEC Networks 1994 SR-TSVOO227S Foreword Issue AprIl 1994
xlv
BOC Notes on the LEC Networks 1994 SR-TSV-002275 Contents Issue AprIl 1994
SectIon Overview Contents
1-1 Overview ..... 11 Section Loca.1 Access and Transport Areas 12 Section Nuinbering Plan and Dialing Procedures 1-2 Section Network Design and Configuration 1-2 Section Billing Customer Data and ControL
.. 12 Section Signaling ...... 13 Section Transn3ission...... _._..._._.. 1-3 Section 8Operations and Maintenance 13 Section Conirnon Systems ...... n .. 1-3 Section 10 Surveillance and Control _...... _ 13 Section Synchronizati ....
.. 1-4 Section 12 Distribution...... _...... Section 13 Terminal Equipment and Premises Wiring
...... 14 Interconnection ...... and Services 1-4 Section 14 Network Architectures ...... 15 Section 15 Exchange Access ...... fl ...... 1-5 Section 16Mobile Services Interconnection.....-...... - ...... 1-5 Section 17 Open Network Architecture...... 1-5 Section 18National Industry Forums and Standards Committees..... BOC Notes on the LEC Networks 1994 SR-TSV-002275
Contents Issue AprIl 1994
5-
II SR-TSV-002275 BOC Notes on the LEC Networks 1994 Overview Issue ApiiI 1994
Overview
BOC Notes on the LEG Networks is widely recognized telecommunications primer presenting an encyclopedia-style overview of numerous technologies and topics regarding todays Local Exchange Carrier LEC networks Notes deals with complex
the in that makes it accessible highly technical subjects but presents information way
and first and understandable to variety of readers Notes has two purposes at glance these seem contradictory It must serve as reference document for the technical reader of information This is generally an easy audience to write for because it is the transfer reader that is important However Notes has second audience the non-technical
This person wants informationbutdoes not want to have to distill fewsimple truths
from technical language So Notes is written and organized to meet the needs of both
groups of readers
The Table of Contents is comprehensive and probably will be most useful to the
technical reader This is reference document and section titles that are useful to the
technical reader may not be very useful to the non-technical reader For that reason we
have included this overview and provided introductory material at the beginning of each
section brief of the of each The following paragraphs provide very description purpose section These will help guide non-technical readers to those sections of Notes that
contain the information they need Once there introductory material in each section will
provide more specific information Each section is followed by Reference list and Bibliography for further reading
The last section of Notes is the Glossary which contains acronyms abbreviations definitions and symbols The telecommunications industry like any other highly
technical and growing industry has its own language The non-technical reader may
from time to time encounter words or phrases that are not familiar so the Glossary is included as guide to meaning and usage For this issue an Index has been added to the
document to provide easier access to particular subject
Notes is not comprehensive document nor is it requirements document Further each
LEC designs and implements its network based on its individual business plans covered in this Therefore the parameters and configurations of some networks are not
document Special services experimental services and services not yet commonly
deployed are not discussed
Section Local Access and Transport Areas
Local Access and Transport Areas LATAs define geographic location based on
number of non-geographic considerations Most LECs recognize the LATA as the the of that boundary of their service area Notes only addresses part message originates
and completes within these boundaries Listed by region is each LATA and the associated Numbering Plan Areas NPAs
11 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Overview Issue AprIl 1994
SectIon NumberIng Plan and Dialing Procedures
In order to be delivered messages must be uniformly addressed via unique telephone network number and routed The calling customer supplies much of the address and the adds the remainder of the address and usually defines call routing There are many networks and geographic destinations so standardization of the telephone numbering that within and plan and dialing procedures is critical to ensure telecommunication between networks can occur The growth in the number of messages has necessitated expansions and changes in the numbering plan and dialing procedures
SectIon Network Design and Configuration
and other Networks are configured based on variety of economic statistical principles
its Network configuration and its designed routing determines how message travels to destination While most messages are dialed by the customer and handled within the
LEC networks additional entities or services interexchange carriers or operator
the telecommunications assistance are available The customer expects reliability from service networks which are regularly evaluated to ensure high level of end-to-end
Section Billing Customer Data and Control
of the for Message information is recorded usually in the early stages call accounting detail and/or billing or routing purposes Customers who require additional message control of their network configuration can purchase LEC services where available that of limited of the allow access to private call detail and/or customer management parts customer network serving arrangement
Section 6SignalIng
the of Signaling refers to the sending and receiving of control information between parts
telecommunications network handling message These signals determine message status routing handling control functions billing and access capability to other networks Each network part must have consistent signaling protocols to handle carried either the routes messages within and between networks This information is on shared or channels controlled circuit-associated signaling or it travels on separate common channel used to convey this information Due to the almost overwhelming number of potential combinations of terminal equipment switching systems operations systems and other network parts vast amount of information must be available to address maximum of typical message delivery possibilities
1-2 BOC Notes the LEC Network 1994 SR-TSV-002275 on OvervIew Issue AprIl 1994
SectIon TransmissIon
that will or its Any message is subject to variety of conditions improve impair transmission Network architecture describes the various necessary parts that provide
Each network has set of conditions to which it is end-to-end message connectivity part vulnerable and that must be considered as messages are passed through LEC networks
SectIon Operations and Maintenance
travel one or more switching systems in Virtually every message must physically through an effective overall at least one network before reaching its destination Therefore
reasonable cost is maintenance plan to provide high-quality service at imperative between Because switching and support systems are closely related within and networks other related Continued inadequate maintenance in any one system can affect any system in number and of automation necessitated by the rapid growth complexity messages evolved and maintenance requires highly diagnostic plans
SectIon Common Systems
there features common to almost While there are many types of switching systems are for the switch every type These common systems include the building systems physical the and the cross-connect location systems that provide power to switching equipment functions in addition to as the where the line systems that perform multiple acting point or channel connects to the switching system
Section 10 Surveillance and Control
To ensure the economical use of networks and to maintain vital telecommunications with surveillance and control services networks are commonly equipped capabilities.
for network traffic network servicing and service These capabilities allow management of level of evaluation Network survefflance and control also ensure maintenance high and the network elements utilization minimize the effect of network overloads support
to National Bell Operating Companies BOCs commitment Security Emergency
Preparedness NSEP
SectIon 11 Synchronization
function well on its internal stand-alone unit of digital equipment may relying solely when units are connected via digital facilities timing source However two or more
is Without messages are synchronized clock sources or timing required synchronization lost or erroneously repeated
14 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Overview
SectIon 12 DistributIon
to individual customers In The distribution network is where the network connects order in which the extends from the descending size order which coincides to the facility distribution network order is feeder plant switching system to the customer the typical the to the network The distribution plant and the loop that connects customer radio or distribution network can be composed of metallic cable fiber-optic cable electronic or cross-connect equipment combination of the three and frequently includes
SectIon 13 Terminal Equipment and Premises Wiring Interconnection
such data In addition to network access via loop terminal equipment as telephone must be connected with the Public Switched terminal or private switching equipment Federal Commission rules exist Telephone Network PSTN Communications FCC tolerances and interconnection regarding terminal equipment manufacture shipping the network from harm Compatibility characteristics to protect public potential of the customer and the LEC requirements are specified and respective responsibilities the are defined This section contains general information on FCC registration program
and the demarcation point specifications
SectIon 14 Network Architectures and Services
to meet their telecommunications needs Many customers require additional capabilities still use or all of the public These services provide specialized features but generally part and network These architectures and the services they enable are relatively new actively include CLASSSM services Alternate evolving The services presented in this section Base Advanced Intelligent Network AThD Billing Service ABS 800 Data Service Service Control Point Services Digital Network ISDN Integrated ISCP Integrated based Broadband Services Digital Asynchronous Transfer Mode ATM Integrated Public Packet Switched Network BISDN Public Switched Digital Service PSDS Data Service and Service PPSS Frame Relay FR Switched Multi-megabit SMIS Common Channel is basic Synchronous Optical Network SONE1 Signaling CCS
first services listed above PSDS PPSS SMDS FR building block of the seven of the and also and SONET while not based on CCS are new services or architectures are also included in this section Service enabling technologies some CCS-based are the interface include described These evolving technologies designed to simplify user Voice Activated and the Analog Display Services Interface ADSI Dialing VAD Voice Activated Network Control VANC
CLASS is service mark of Beilcore
1-4 Notes the LEC Network 1994 SR-TSV.002275 BOC on
Issii April 1994
Section 15 Exchange Access
that extend In most cases LECs are precluded from providing network services beyond entities as their boundaries Exchange access is provided to interconnecting such that these entities can telecommunication interexchange carriers by LECs so provide
services between LATAs interLATA to end-user customers
SectIon 16 Mobile Services Interconnection
Wireless Services Providers WSPs offer services using radio as their transmission interconnection with the LEC networks medium under FCC license WSPs require of which are Mobile wireless carrier interconnection has shown signs rapid change
addressed in this section
Section 17 Open Network Architecture
is created the FCC to further Open Network Architecture ONA regulatory concept by
the full benefits of the Information to the American the FCCs goals of bringing Age offer unbundled Basic public The FCC requires the BOCs to Serving Arrangements BSAs and Basic Service Elements BSEs under tariff so Enhanced Service Providers section defines the elements ESPs can access them to provide enhanced services This
and arrangements
Committees Section 18 National Industry Forums and Standards
standards The Alliance for Telecommunications Industry Solutions ATIS is major of national and international telecommunications body whose mission is the resolution the of issues involving technical interconnection standards as well as development The has to encompass wide range of open operational guidelines organization grown broad of national access service issues industry forums which resolve spectrum and and numbering This including billing installation testing maintenance reliability the committees and forums section describes the mission and issues addressed at eight
and their working subcommittees
1-6 BOC Notes on the LEC Networks 1994 SR-TSV-002275 1994 OvervIew Issue AprIl
14
BOC Notes on the LEC Networks 1994 SR-TSV-002275 Contents Issue April 1994
Section
Local Access and Transport Areas Contents
2-1 Local Access and Transport Areas 2-1 2.1 LATA Design Requirements 2-3 2.2 Design Exceptions 2-4 2.3 BOC Relationship with Other Exchange Companies LATA 2.4 BOC Offshore International and Independent 24 Assignments 217 Iteferences 2-19 Bibliography SR-TSV-002275 BOC Notes on the LEC Networks 1994 Contents Issue April 1994
List of Tables
Table 2-1 Numerical LATA Assignments NYNEX 2-5
Table 2-2 Numerical LATA Assignments Bell Atlantic 2-6
2-7 Table 2-3 Numerical LATA Assignments Ameritech
2-8 Table 2-4 Numerical LATA Assignments BellSouth
Table 2-5 Numerical LATA Assignments Southwestern Bell Telephone 211 Conipany
Table 2-6 Numerical LATA Assignments WEST 212
2-13 Table 2-7 Numerical LATA Assignments Pacific Telesis
Table 2-8 Numerical LATA Assignments Offshore and International
L.istins 213
Table 2-9 Numerical LATA Assignments Independents 2-14
II Notes on the LEC Networks 1994 SR-TSV-002275 BOC Local Access and Transport Areas Issue April 1994
Local Access and Transport Areas
of divestiture of the Bell Companies the Modification As part of the Operating BOCs and Final Judgment MFJ called for the separation of exchange interexchange telecommunications functions Exchange services can be provided by BOCs than BOC entities interexchange services are to be provided by other
Areas also referred New service territories called Local Access and Transport LATAs
created in to the MFJ to as service areas by some BOCs were response exchange-area basic requirements LATAs serve the following two purposes
the BOCs offer They provide method for delineating the areawithin which may
services
of the former Bell were They provided basis for determining how the assets System divestiture to be divided between the BOCs and ATT at
to offer BOC end Appendix of the MFJ requires each BOC equal access through All carriers must be offices in LATA to all Interexchange Carriers ICs provided those to In services that are equal in type quality and price to provided ATT general such services include but are not limited to providing network-control signaling answer Carrier Access Codes supervision automatic calling-number identification CACs and data directory services testing and maintenance of facilities billing
2.1 LATA Design Requirements
for the establishment of LATAs The MFJ Section IV 9.1-4 contains specific guidelines
These Court-approved requirements are listed below
local common Any area may encompass one or more contiguous exchanges serving transcends social economic and other purposes even where such configuration
municipal or other local-government boundaries
within an area Every point served by BOC within state will be included exchange
Statistical Area Any area that includes part or all of one Standard Metropolitan Area in the case of densely SMSA or Standard Consolidated Statistical SCSA include substantial of other populated states needs Court approval to part any
SMSA or SCSA
located in state include Except with Court approval no exchange area one may any within another state point located
nucleus SMSAs became the new basis for BOC service areas large-population for
and the United States Government for the of gathering An SMSA is geographic area defined by purpose
reporting federal statistics
2-1 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Local Access and Transport Areas
of economic and social example city and its adjacent communities have high degree have need to communicate with each other SMSAs provide integration and therefore the boundaries within which federal agencies compile information on population SCSAs are housing industry trade employment and wide range of other subjects combinations of two or more related SMSAs
Under current SMSAs are designated and defined according to published specifications
for SMSA if it contains of at least guidelines an area qualifies recognition as an city urbanized with of that is 50000 people or if it contains an area population 50000 part had of total metropolitan-area population of at least 100000 The federal government the SMSAs were previously designated total of 323SMSAs nationwide Fiftyof number of combined to form 17 SCSAs As result of the latest review process both the
and terminology for statistical areas have changed
and On June 30 1990 there were 263 Metropolitan Statistical Areas MSAs 20 to Consolidated Metropolitan Statistical Areas CMSAs These are roughly equivalent called SMSAs and SCSAs respectively However CMSAs are composed of 71 areas service in Primary Metropolitan Statistical Areas BOCs are the predominant providers 220 of the MSAs and 17 of the CMSAs But in some cases for example Los Angeles numbers of subscribers other Local Exchange Carriers LECs also serve significant
Several characteristics of MSAs have an impact on LATA design By definition MSAs
do all areas served the designate only metropolitan areas and therefore not cover by BOCs MSAs are sometimes contiguous making the identification of separate follow communities-of-interest difficult from telecommunications perspective MSAs
coincide with local or wire center county boundaries that frequently do not exchange boundaries For these and other reasons LATAs do not directly overlay MSAs of LATAs However the MFJ relies heavily on the use of MSAs in the configuration
There are several reasons for this
MSAs were defined by the federal government
MSAs have become widely accepted method of defining meaningful population
groups
remain intact Using MSAS allows areas with high community-of-interest to
Based on the guidelines provided by the MPJ the BOCs designed LATAs to encompass
2-7 list the 164 BOC LATAs all areas now served by the BOCs Tables 2-1 through
approved by the Court
2-2 the LEC Networks SR-TSV-002275 BOC Notes on 1994 Local Access and Transport Areas Issue AprIl 1994
2.2 Design Exceptions
boundaries and The Court recognized the need for flexibility in determining LATA the provided for waiver process in each case where waiver was requested of the factors responsible BOC provided the Court with detailed description underlying considerations determined the of the request Economic factors and customer type where the Court was convinced exception requested Specific exceptions were granted that there were compelling economic or service reasons In most cases permanent and In other the exceptions from MFJ guidelines were requested approved cases exceptions applied for were temporary in nature
if forced into Generally permanent exceptions were sought whereLATA configurations economic In each MFJ guidelines would have created negative social and consequences contradict the and case care was taken to ensure that the exceptions did not spirit purpose of the MFJ Exceptions were requested to accomplish the following
Service Continue existing service arrangements such as flat-rate Extended-Area
EAS and privileged-business
include nonsubstantial markets
boundaries Preserve existing wire center
Preserve existing communities-of-interest
Minimize disruption to end office toil trunking
Minimize impact on customers
include tandem arrangement
the Permanent exceptions were requested for LATAs that did not fully meet boundary with boundaries requirements contained in Section 2.1 and LATAs were approved substantial MSAICMSA crossing state lines and containing parts of more than one
Some LATAs required exceptions for both reasons
certain In some instances exceptions were requested to permit the BOCs to provide types of interLATA services Permission to continue existing long-standing BOC local-calling the Court in arrangements and EAS across LATA boundaries were granted by addition limited corridor exceptions were required to preserve traditional direct BOC interstate interLATA serving arrangements These exceptions called for BOC-to-BOC trunking and between of the between for example portions of the New Jersey LATAs portions
the LATA Philadelphia LATA and portions of Delaware Valley NJ
and number of LATAs were approved that contained one MSA/CMSA were in these cases nonsubstantial part of another MSA/CMSA No exceptions required
2-3 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Local Access and Transport Areas April
2.3 BOC Relationship with Other Exchange Companies
of The MFJ does not impose equal access obligation on other LECs restrict the lines business in which they may engage nor restrict the types of services they may provide
Furthermore there is no deadline on the decision by independent LECs regarding the interexchange of traffic to or from BOC LATAs and associated areas Under Federal Communications Commission FCCrules independent LECs are also required to when that does not provide equal access upon receipt of bona fide request request to the LEC present an undue implementation burden independent LATAs Analysis of traffic between independent LEC-served areas and BOC was for the necessary to determine the nature of the traffic interLATA versus intraLATA the BOCs could serve purpose of asset assignment and to clearly delineate the areas the under the decree in The Department of Justice DOJ defined proper approach as
it served general treating the territory served by an independent company as were by
if BOC Thus if the traffic or facility arrangement would not violate the decree the
it would be deemed in violation of the decree territory at issue were served by BOC not in the by the DOJ if served by an independent company In addition guidelines to assist
classification of traffic were also provided by the DOJ
The Court has approved the associations of independent LEC exchanges as proposed by and BOCs the BOCs and modified by the DOJ However because the independent LECs
needed the association must negotiate the business arrangements to implement changes of can result In the future BOC can petition the Court for revised classification
traffic particular BOC/independent LEC
2.4 BOC Offshore International and Independent LATA Assignments
Tables 2-1 through 2-9 provide the LATA assignments for BOCs offshore and also international companies and independent companies -These assignments are
contained in the Local Exchange Routing Guide LERG which is issued quarterly on and microfiche.1 paper and monthly on data tape
2-4 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Local Access and Transport Areas Issue April 1994
Table 2-1 Numerical LATA Assignments NYNEX
LATA LATA Name NPA
120 Maine 207
122 New Hampshire 603
124 Vermont 802
126 Western Massachusetts 413
128 EasternMassachusetts 617508
130 Rhode Island 401 917 132 New York Metro New York 516 212 914 203 718
133 Poughkeepsie New York 914717
134 AlbanyNewYork 518413
136 Syracuse New York 315607
138 Binghamton New York 607 717
140 Buffalo New York 716 814
Numbering Plan Area
2-5 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Local Access and Transport Areas Issue April 1994
Table 2-2 Numerical LATA Assignments Bell Atlantic
LATA LATA Name NPA
220 Atlantic Coastal New Jersey 609
222 Delaware Valley New Jersey 609
224 North Jersey New Jersey 201 215 609 908
226 Harrisburg Pennsylvania 717 814 215 301
228 Philadelphia Pennsylvania 609215 302
230 Altoona Pennsylvania 814
232 Northeast Pennsylvania 717 215 201 814
234 Pittsburgh Pennsylvania 412
236 Washington DC 301 202 703410
238 Baltimore Maryland 301410
240 Hagerstown Maryland 301 304 814 717410
242 Salisbury Maryland 301410
244 Roanoke Virginia 703 615
246 Culpeper Virginia 703 804
248 Richmond Virginia 804
250 Lynchburg Virginia 804919
252 Norfolk Virginia 804 703 919
254 Charleston West Virginia 304 703 202
256 Clarksburg West Virginia 304412
2-6 SR.TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Local Access and Transport Areas
Table 2-3 Numerical LATA Assignments Ameritech
LATA LATA Name NPA
320 Cleveland Ohio 216
322 Youngstown Ohio 216 412 324 Columbus Ohio 614
325 Akron Ohio 216
326 Toledo Ohio 419313371
328 DaytonOhio 513
330 Evansville Indiana 812
332 South Bend Indiana 219
334 Auburn-Huntington Indiana 219419
336 Indianapolis Indiana 317217219
338 Bloomington Indiana 812 618
340 Detroit Michigan 313 517419
342 Upper Peninsula Michigan 906715
344 Saginaw Michigan 517
346 Lansing Michigan 517
348 Grand Rapids Michigan 616 517 350 Northeastern Wisconsin 414 715 906
352 Northwestern Wisconsin 715 612
354 Southwestern Wisconsin 608 815
356 Southeastern Wisconsin 414 815 608 715
358 Chicago Illinois 312 414 815 219 708
360 Rockford Illinois 815 608
362 Cairo Illinois 618
364 Sterling Illinois 815
366 Forrest Illinois 815 309 217
368 Peoria illinois 309815217618
370 Champaign illinois 217
374 Springfield Illinois 217
376 Quincy Illinois 217
2-7 BOC Notes on the LEC NetworksI 994 SR-TSV-002275 Local Access and Transport Areas Issue April 1994
Table 2-4 Numerical LATA Assignments BellSouth
LATA LATA Name NPA
420 Asheville North Carolina 704
422 Charlotte North Carolina 704 803
424 Greensboro North Carolina 919 704
426 Raleigh North Carolina 919
428 Wilmington North Carolina 803 919
430 Greenville South Carolina 704 803
432 Florence South Carolina 803
434 Columbia South Carolina 803
436 Charleston South Carolina 803
438 Atlanta Georgia 205404706
440 Savannah Georgia 803 912
442 Augusta Georgia 404 803 912706
444 Albany Georgia 912
446 Macon Georgia 912
448 Pensacola Florida 904 205
44813 Pensacola Florida WAEA 904205
44814 Pensacola Florida CREA 904205
44815 Pensacola Florida FWEA 904
450 Panama City Florida 904912
45009 Panama City Florida PCEA 904
__ In Florida only 5-digit LATA numbers exist which represent Equal-Access Exchange Areas EAEAs Based on Florida Public Service Commission Order 13750 Docket 820537-1 of October 1984
EAEAs are geographic areas configured based on 1987 planned toll center/access tandem areas in in which the Felephone Company is responsible for providing equal access to both carriers and endusers the most economically efficient manner In an EAEA ICs interexchange carriers and resellers may in have one or more points of presence so long as any additional costs incurred by the Company such location providing such alternate or additional point of presence be paid by the party choosing as
primary point of connection will be provided by the Company in each EAEA
2-8 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Local Access and Transport Areas Issue April 1994
Table 2-4 Numerical LATA Assignments BellSouth Continued
LATA LATA Name NPA
45010 Panama City Florida SJEA 904912
45011 Panama City florida QCEA 904
45012 Panama City Florida MREA 904
452 Jacksonville Florida 904
45204 Jacksonville Florida CLEA 904
45205 Jacksonville Florida LOEA 904
454 Gainesville Florida 904
45402 Gainesville Florida NWEA 904
45403 Gainesville Florida OLEA 904
456 Daytona Beach Florida 904
45601 Daytona Beach Florida POEA 904 458 Orlando Florida 305 904407
45806 Orlando Florida OREA 305 407
45807 Orlando Florida LBEA 407
45808 Orlando Florida WIEA 904407
460 Southeastern Florida 305 407
46017 Southeastern Florida GG-EA 305
46018 Southeastern Florida GR-EA 407
462 Louisville Kentucky 502 812
464 Owensboro Kentucky 502 615 901
466 Winchester Kentucky 606615
numbers which Equal-Access Exchange Areas EAEAs In Florida only 5-digit LATA exist represent Order Docket 820537-TP of October 1984 Based on Florida Public Service Commission 13750 based on 1987 toll center/access tandem areas in EAEAs are geographic areas configured planned to both carriers and endusers in which the Telephone Company is responsible for providing equal access In ICs interexchange carriers and resellers may the most economically efficient manner an EAEA additional costs incurred by the Company in have one or more points of presence so long as any such location as additional of be paid by the party choosing providing such alternate or point presence will be the Company in each EAEA primary point of connection provided by
2-9 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Local Access and Transport Areas
Table 2-4 Numerical LATA Assignments BellSouth Continued
LATA LATA Name NFA
468 Memphis Tennessee 901 502 601
470 Nashville Tennessee 615 205 502
472 Chattanooga Tennessee 615205404704706
474 Knoxville Tennessee 615 606704
476 Birmingham Alabama 205
477 Huntsville Alabama 205601
478 Montgomery Alabama 205 912 480 Mobile Alabama 205904601 901 482 Jackson Mississippi 601 504 205 318
484 Bioxi Mississippi 601504
486 Shreveport Louisiana 318 501214
488 Lafayette Louisiana 318
490 New Orleans Louisiana 504 601 492 Baton Rouge Louisiana 504
2.10 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Local Access and Transport Areas
Table 2-5 Numerical LATA Assignments Southwestern Bell Telephone Company
LATA LATA Name NPA
520 St Louis Missouri 314 618
521 Westphalia Missouri 314
522 Springfield Missouri 417 316 501 918
524 KansasCityMissouri 816913417712
526 Fort Smith Arkansas 501417918
528 Little Rock Arkansas 501314918901
530 PineBluffArkansas 501318
532 Wichita Kansas 316 303 405 417 913 918
534 Topeka Kansas 913 308 402 303
536 Oklahoma City Oklahoma 405 806
538 TulsaOklahoma 918316
540 El Paso Texas 915 505
542 Midland Texas 915
544 Lubbock Texas 806
546 Amarillo Texas 806405 303 505
548 Wichita Falls Texas 817
550 Abilene Texas 915
552 Dallas Texas 214817903
554 Longview Texas 501 903 556 Waco Texas 817
558 Austin Texas 512
560 Houston Texas 713409 562 Beaumont Texas 409
564 Corpus Christi Texas 512 566 San Antonio Texas 512210
568 Brownsville Texas 512 210
570 Hearne Texas 409
2-11 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Local Access and Transport Areas Issue April 1994
Table 2-6 Numencal LATA Assignments WEST
LATA LATA Name NPA
620 Rochester Minnesota 507 319 605 712 515 624 Duluth Minnesota 218 715
626 St Cloud Minnesota 612 605 218
628 Minneapolis Minnesota 612 218 507
630 Sioux City Iowa 712 402 605 507
632 Des Moines Iowa 515 319 507 712 816
634 Davenport Iowa 319 309 608 815 816
635 Cedar Rapids Iowa 319 507
636 Brainerd-Fargo North Dakota 701 218 605
638 Bismark North Dakota 701 406605 640 South Dakota 605 307 308 402406 507 701 712
644 Omaha Nebraska 402 712 308 816
646 Grand Island Nebraska 308 303 307 605 913
648 Great Falls Montana 406208
650 Billings Montana 406 307 701
652 Idaho 208503801702307509 654 Wyoming 307 303406 208 308 605 801 656 Denver Colorado 303 307 308
658 Colorado Springs Colorado 303 719
660 Utah 801 602 208 702 303 503 664 New Mexico 505 915
666 Phoenix Arizona 602 619 801
668 Thcson Arizona 602 505
670 Eugene Oregon 503 916
672 Portland Oregon 503 206 509
674 Seattle Washington 206
676 Spokane Washington 208 503 509
2-12 the LEC Networks 1994 SR-TSV-002275 BOC Notes on Local Access and Transport Areas Issue April 1994
Table 2-7 Numerical LATA Assignments Pacific Telesis
LATA LATA Name NPA
720 Reno Nevada 702916503
721 Pahrump Nevada 702
722 San Francisco California 415 707 408 510
724 Chico California 916
726 Sacramento California 916
728 Fresno California 209 909 730 Los Angeles California 213 714 818 619 602 805 310
732 San Diego California 619
734 Bakersfield California 805
736 Monterey California 408
738 Stockton California 209
740 San Luis Obispo California 805
International Table 2-8 Numencal LATA Assignments Offshore and Listings
LATA LATA Name NPA
820 Puerto Rico 809
822 Virgin Islands 809 824 Bahamas 809
826 Jamaica 809
830 Other Caribbean Islands 809
832 Alaska 907
834 Hawaii 808
836 Midway-Wake 808
2-13 BOC Notes on the LEC Networks 1994 SR-TSV-002275 1994 Local Access and Transport Areas Issue April
Table 2-9 Numerical LATA Assignments lndependents
LATA LATA Name NPA
920 Connecticut SNET 203
921 Fisher Island New York 516
922 Cincinnati Ohio 513 606 812
923 Lima-Mansfield Ohio 216419 513 614
924 Erie Pennsylvania 814
927 Harrisonburg Virginia 703
928 Charlottesville Virginia 703 804
929 Edinburg Virginia 703
930 Eppes Fork Virginia 804
932 Bluefield West Virginia 304 703
937 Richmond Indiana 317513
938 Terre Haute Indiana 217812 939 Ft Myers florida 813
949 Fayetteville North Carolina 919
951 Rocky Mount North Carolina 919804 952 Tampa Florida 813
953 Tallahassee Florida 904
956 Bristol-Johnson City Tennessee 615 703
958 Lincoln Nebraska 402 712 913
960 Couer DAlene Idaho 208509406
961 San Angelo Texas 915
963 Kalispell Montana 406
973 Palm Springs California 619
An administrative LATA 999 exists for use in identifying Service Access Codes SACs in the Local
Exchange Routing Guide LERG only
2-14 SOC Notes the LEC Networks 1994 SR-IS V-002275 on Local Access and Transport Areas Issue April 1994
Table 2-9 Numerical LATA Assignments lndependents Continued
LATA LATA Name NPA
974 Rochester New York 716
976 Mattoon Illinois 217
977 Macomb illinois 309 217
978 Olney Illinois 618
980 Navajo Territory Arizona 602
981 Navajo Territory Utah 801
Access Codes in the Local An dniinistrative LATA 999 exists for use in identifying Service SACs
Exchange Routing Guide LERG only
2-15 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Local Access and Transport Areas Issue April 1994
2-16 the LEC Networks SR-TSV-002275 BOC Notes on 1994 Local Access and Transport Areas Issue AprIl 1994
References
TR-EOP-000085 through TR-EOP-000092 or TR-EOP-000315 Local Exchange
Routing Guide LERG Beilcore March 1994
Issued quarterly
TR-EOP-000085 Vol NYNEX 100-Series LATAs
TR-EOP-000086 Vol Bell Atlantic 200-Series LATAs
TR-EOP-000087 Vol Ameritech 300-Series LATAs
TR-EOP-000088 Vol.4 BellSouth 400-Series LATAs
TR-EOP-000089 Vol.5 Southwestern Bell 500-Series LATAs TR-EOP-000090 Vol WEST 600-Series LATAs
TR-EOP-000091 Vol Pacific Telesis 700-Series LATAs
TR-EOP-000092 Vol Offshore and International 800-Series LATAs
Independents 900-Series LATAS
TR-EOP-000315 All eight volumes
Issued monthly
TR-EOP-000315 Ti 6250 bpi LERG Data Tape
TR-EOP-000315 T2 1600 bpi LERG Data Tapes
TR-EOP-0003i5 LERG Microfiche
NOTE
and their citation in this document reflects All Bellcore documents are subject to change
Readers are advised to the most current information available at the time of this printing
check current status and availability of all documents
To obtain Beilcore documents contact
Beilcore Customer Relations
Corporate Place Room 3A-i84
Piscataway NJ 08854-4156
1-800-521-CORE
908 699-5800 for foreign calls
document coordinator and Beilcore BCC personnel should contact their company
obtain documents personnel should call 908 699-5802 to
2-17 BOC Notes on the L.EC Networks 1994 SR-TSV-002275 Issue April 1994 Local Access and Transport Areas
2-18 BOC Notes on the LEC Networks 1994 SR-IS V-002275 Local Access and Transport Areas Issue April 1994
Bibliography
NJ March TR-EOP-000315 all volumes issued quarterly Beilcore Piscataway
1994
2-19 BOC Notes on the LEC Networks 1994 SR-TSV-002275 1994 Local Access and Transport Areas Issue AprIl
2-20
SR-TSV-002275 BOC Notso on the LEC Networks 1994 Contents Issue AprIl 1994
SectIon Numbering Plan and
Dialing Procedures Contents
3-1 Numbering Plan and Dialing Procedures ...... 3.1 NA.N1 Number Structure 32
3.2 Numbering Plan .A.reas_ ...... 32
3.2.1 NPA Code Format and Capacity .. rn...... 35 3.2.2 NPA Code ssignment.._.._._ ..._...... 3-6
3.3 Service Access Codes ...... _ ...... 36
3.3.1 Media Representation of Service Access Codes 3-7
3.4 Ni Service Codes 38 ...... _ 3.4.1 Unassigned Service Coles...... 38
3.4.2 Universal Emergency Number ...... 3-8 38 3.5 entral office Codes ......
3.5.1 Central Office Code Format and Capacity ...... _ 3-8
3.5.2 entrai office Code Assignments 39 3-10 3.5.3 Interchangeable Central Office Code Assignment...... 3.5.4 Code Conservation and Relief ..._ 310 3.6 Implementing Interchangeable Codes ..... 3-12 3.6.1 Interchangeable Numbering Plan Area Codes 3-12
3.6.2 Implementing Interchangeable Central Office Codes...... 3-13
3.6.2.1 PrefIx 314 Method ...... __...... _ ......
3.6.2.2 liining Ivlethod...... 314 314 3.6.2.3 Hybrid Method ...... _...... m....
3.7 Telephone Nurnbers...._ ...... n.....n..n...m..n...nnn.n. 316 316 3.7.1 Ithunbering ...... _
3.7.2 Coin Station Numnbering...._...o...... nan.nm...n...nnnn.n...n...n..n 317 317 3.8 Iialing Procedures ...... __...... _...._.__.._._._._. 317 3.8.1 R.econunended Jialing Procedures ...... _ 3-18 3.8.2 Dialing Procedure Objectives...... _ ...... 319 3.9 tialing Prefixes for Carrier Selection ...... 320 3.10 Operator Assistance ......
.. 320 3.1 International lirect list.ance Iiaiing 3.12 000 arid 1XX Codes 321 3-22 3.13 Special Characters and _...... 323 3.14 Vertical Service Codes ...... 32.3 3.15 SS7 Point Codes ...... fl...e ...... _...._ 3-24 3.16 Automatic Number Identification II Digit Assignments......
References ..... 333 335 Bibliophy .._...... nnn..n.nnnn BOC Notes on the LEC Networks 1994 SR-TSV-002275 1994 Contents Issue AprIl
List of Figures
34 Figure 3-1 International Telephone Number Format ...m..
3-3 Figure 3-2 U.S Numbering Plan Areas with Codes......
II SR-TSV002275 BOC Notes on the LEC NetworksI 994 Contents Issue AprIl 1994
List of Tables
32 Table 31 NA.N1 Telephone Number Format
3-8 Table 3-2 Service Code Assignments......
3-12 Table 3-3 Noninterchangeableflnterchangeable Codes._.
3-13 Table 3-4 Interchangeable NPA Code Conversion 315 Table 35 Hybrid Ivtethod ...... n......
Table 3-6 Recommended Dialing Procedures for Locations with SXS 3-25 Equipment ......
Table 3-7 Recommended Dialing Procedures for Locations without SXS 326 Equiplnent ......
Table 3-8 Recommended Dialing Procedure for Directory Assistance Under 327 Feature C3roup D...... _......
Table 3-9 Treatment of And 00 Dialed Calls from Equal-Access End 32.8 offices ...._...... _....._....__._n
with 3-29 Table 3-10 Dialing Procedures Available Feature Group
3-30 Table 3-11 NPA Codes in Alphabetical Order as of February 1994
3-31 Table 3-12 NPA Codes in Numerical Order as of February 1994... BOC Notes on the LEC NetWOrks 1994 SR-TSV-002275 Contents Issue AprIl 1994
Iv BOC Not. on the LEC Networks 1994 SR-TSV-002275 Numbering Plan and Dialing Procedures Issue April1994
Numbering Plan and Dialing Procedures
standards established All telephone numbering plans for public networks conform to by Standardization the International Telecommunication UnionTelecommunication World Sector ITIJ-1V These numbering plans divide the world into nine geographic 1TLJ-T codes Zones numbered through Within each World Zone assigns country
them in Recommendation E.164 codes are 12 or digits in length and reports Country of the World Zone in which the is and the first digit is always the number country
and is located World Zone for example has an integrated numbering plan assigned
shared 18 countries in North America Within this area country code which is by American Plan national numbers are formatted according to the North Numbering local NAN Within the geographic area designated for each country code the Recommendation E.164 administration may define its own national numbering plan format shown in 3-1 defines international telephone numbers to be in the Figure
Number Country Code CC National Significant NSN
lto3Digits iirI
Maximum of 12 Digits rf
Format Figure 3-1 International Telephone Number
code and national number cannot The combined length of the country significant E.164 increases this number to 15 at Time exceed 12 digits Recommendation digits Coordinated which has been designated as December 31 1996 at 1159 p.m numberof Universal Time There are no plans inthenear future to increase the will be calls within the area served by NAN However there digits dialed to complete of international calls increases in the number of digits required for completion some
of the was vested in Beilcore the Court in At divestiture the administration NANP by Amendment No 33 of the Plan of Reorganization POR However Beilcore has and/or announced its intention to relinquish this responsibility pending industry
of the issue regulatory resolution
and Consultative Committee CClfl Formerly the International Telegraph Telephone
3-1 BOC Notes on the LEC Ntworka 1994 SR-TSV-002275
Numbeing Plan and Dialing Proc.durss Issue AprIl 1994
3.1 NANP Number Structure
main in the The NANP is based on destination code principle where each telephone numbers NANP has specific address or destination code assigned to it NANP are in the 10-digit format shown in Table 3-1
Table 3-1 NANP Telephone Number Format
3-Digit 3-Digit 4-Digit Numbering Central Station Plan Office Number Area NPA Code N0/1X YJOOC
Legend Nisanydigit2-9
Xis anydigit0-9
0/1 is either or
In NPAs where interchangeable Central Office codes have been implemented see Section 3.4
the format for the Central Office code is NXX
and format See Section 3.2.1 regarding Interchangeable NPA INPA codes O/l
change to NXX
NANP numbers generally define geographic hierarchy The area served by the NANP is divided into distinct exclusive geographic areas each of which is assigned
Numbering Plan Area NPA code Central Office codes NNX/NXX are typically basic assigned to switching entities/points of interconnection that provide switching functions within each NPA Each Central Office code..can serve as many as 10000
subscriber lines or station numbers The subsections that follow describe NPAs Central Office codes and station numbers in more detail
3.2 Numbering Plan Areas
the NPA Most NPAs also called area codes identify geographic area map showing boundaries within World Zone is found in Figure 3-2 Tables 3-11 and 3-12 at the end of this section list the NPA codes assigned through February 1994
Certain NPA codes in the format N00 and Nil do not identify geographic area Codes in the format N00 are called Service Access Codes SACs those in the format Nil are called Service Codes The functions of these nongeographic codes are explained in
Sections 3.3 and 3.4 respectively
3-2 8R-TSV-002275 BOC Notes on the LEC NetworksI 994 Numbering Plan and Dialing Procedures Issu April 1994 Numbering Plan Areas With Codes
-- Gulf of BRITISH COLUMBIA St Lawrence NEWFOUNDLAND NADA ONTARI 604 ALBERTA 709 SASKATCHEWAN MANITOBA ISLAND 807 NEW UNSWICK PRINCEARD 306 204 QUEBEC 705 Oueb4c 506 20 Spokane 418 Pacific 819 WAS4INGTON Thunder Ba Atlantic Ocean Po land Ocean 509 NORTH DAKOTA 218 MPJNE North ..514 NOVA SCOTIA MONTANA Superior Ba Duluth Montreal .Eugene Augusta Bismarck 90 Billings Escanab Lake RM 715 OREGON MINNESOTA .Syrcuse or Boise Huron 80 CD 503 612 WISCONSIN -- IFAH 315518 WHAMPSHIRE Minneapolis Paul St -- 416s Alban SOUTH DAKOTA L.Ontario 617 208 --- 616 51or00 414 605 507 La London9OS NEWORK 508 Sioux .Buffal f Worceste Falls Rochester .Bin ha tAVCRAIIi.I MICA-1IGAp ami aAccArwI an ontia Milwukee Lake 71 916 Erie 307 Dubuqt1e adison.\ 517 810 Spnngtid413 Michiga YLVANIA ork City 401 Sacramento 712 IOWA 308 Chag 31 Detrolt PEN81S4 EISLAND 319 16 815 CONNECTICUT 707 Cheyenne -- Mcsnes Toledosiev Harnstyirg NEBRASKA iu So.Bend SaltLake 419 -Piitsb 203 Altona NEVADA City Omaha Counol o9s505r0k 219 ------412 Bluffs 515 614 San Francis orth Platte Peoria O-1IO NEW YORK 5sQakland 702 402 lndia4iapolis 415 .Denver 217 sio UTAH COLORADO Spnngild ....-317 Scicinnt0lU 304 914 IS ND -- ingtons ILLINOIS - anJose Chadest 201 516 801 303 913 INDIANA .Frsno KANSAS VIRGI IA Newark COlorado 5St Louis 812 clichrnond nngs Topeka 816 Centralia Eva Covingt 209 VIGINIA ewBruoewk 917 618 606 719 703 8NEWJER EY\ 316 KENTUCKY 19 ii tow .Wichita 314 .Bakersfteld Stld 805 Greensboro .Raleigh --- 502 Bermuda -- ARIZNA Ofl 142 417 NORTH CALIFORNIA .Nashville 615 CAROLSINK 809 Qaeeno 60 505 704 .Cht1ot1e 405 Tulsa 1ENNESSEE BroO 520 901 619 910 ArIanhcCdy Albuquerque .Amarillo OKLAHOMA 602 918 Memphis ARKANSAS 706 SO CAROLINA Balhnrore 55 ys1nd PhOfli5 .San Diego LitUe Birmingham 803 30 NEW MEXICO 806 Oldahoma 301 City AtI nt Charleston 410 MARYLASJ 205 DELA ARE Burtank fff8------.Tucson Jackson ALABAMA lostge1s 213 GEORGIA waohhue55S SanBemadino DSlLas DC Ft Worth -310-..- -. Sweetwater Shreveport Savannah MARY ND 601 202 214 .Tyter Montgomery Long Beach pa1ieim 912 7-14 TEXAS 817 9O3- 318 MISSISSIPPI 915 RGINIA _- Jacksonville LOUISIANA 409 FLORIDA Pacific 713. 504 904 51 New Orleans Ocean Houston Beaumont 407 San tonio Austin ______Gulf of 813 West Palm Beach 210 Mexico Ft Meyem
Miami 05 905 NPA Ontario Effective October 41993 Bahamas North Carolina November HAWAII \\ 910 NPA 141993 rk
808 lands 610 NPA Pennsylvania January 1994 Wgin Islands 334 NPA Alabama 1995 January 15 The ______Islands 360 NPA Washington State January 15 1995 Cayman Repuet5 Islands 520 NPA Arizona March 19 1995 Anguilla Rico St Kitis Antigua Jamaica Nevis
Montserraf Copyright ellcore 809
1991 Dominica 1984 July Barbados Plan with Codes St Lucia All U.S Areas riqhls reurvcd Figure 3-2 Numbering St Vincent Tobago
Grenada Tnnidad Revised December 1993 3-3 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Plan and Procedures Numbering Dialing Issue April 1994
3-4 LEC Networks 1994 SR-IS V.002275 BOC Notes on the Plan and Procedures issue AprIl 1994 Numbeiing DIaling
3.2.1 NPA Code Format and Capacity
have been in the format In the NANP prior to January 1995 NPAs following
NO/1X
where is any digit through
is any digit through 0/1 iseitherOorl
codes of the format Oil be used as NPA codes except for The NANP specifies that total codes of the format Nil which are reserved for special functions This provides of 152 NPA codes as follows
Maximum NPA codes available with an 0/1 format 160
Less reserved codes of Nil format
Total NPA codes available for assignment 152
in the and solution called Depletion of the NPA pool was foreseen early 1960s in the Interchangeable NPA INPA codes was developed INPA codes are following format
NXX
where is any digit through
is any digit through
which includes the 152 codes in the This NXX format provides total of 792 NPA codes
0/1 format more than fourfold increase
Maximum NPA codes available with NXX format 800 LessreservedcodesofNliformat
792 Total NPA codes available per assignment
including 152 codes in the 0/1 format
NOTE
or The introduction of INPA codes which is scheduled to take place on as described in after January 1995 requires special preparation Section 3.6 BOC Notes on the LEC Networks 1994 SR-TSV002275
Numbering Plan and Dialing Procedures issue AprIl 1994
3.2.2 NPA Code Assignment
Assignment of NPA codes is the responsibility of the NAN Administration NANPA Organization at Beilcore Applications for NPA codes should be directed to the Director
NANP Administration Tables 3-11 and 3-12 show the existing assignment of NPA
codes and SACs Figure 3-2 shows the geographic areas encompassed by each NPA
NPAs were created and designed in ways that maximize caller understanding while
minimizing both dialing effort and equipment cost There are several principles to be
considered in planning NPA boundary changes due to either the introduction of new
NPAs or the realignment of existing NPA boundaries
Where possible boundaries should be drawn to coincide with state province or other
political subdivision boundaries In the United States boundaries must not cross over
state lines
When it is impractical to draw boundaries to coincide with province or other political
subdivision boundaries then the boundaries should follow recognizable physical
geographic features or structures such as rivers large lakes mountain ranges or major highways
Boundaries should be drawn to minimize the splitting of existing and future
communities-of-interest or recognized metropolitan areas
Customers affected by boundary realignment or split should not be subject to
other related for subsequent realignment or numbering changes at least 10 years If this is not feasible the projected time to exhaust for both the old and new NPAs
should be roughly equal
Experience in recent NPA relief has emphasized that planning must include all carriers providing local and cellular service in the affected NPAs and must begin early enough to
adequately inform the public and regulatory bodies of the pending changes See Section
3.5.4 for further discussion of code conservation and relief planning
3.3 Service Access Codes
NPA codes in the format N00 are called Service Access Codes SACs These nongeographic codes have been reserved and allocated to provide caller access to
Interexchange Carriers ICsor Local Exchange Carriers LECs Four SACs are currently assigned 600700800 and 900 In addition another NPA code has SAC like function 710 is assigned to the United States Government
The 600 SAC is mixed service code for Canada NXX codes within the SAC are available to any Canadian carrier that meets assignment criteria SAC 600 is administered by the Canadian Number Administrator in conjunction with the Canadian
Steering Committee on Numbering
The entire range of Central Office codes and line numbers associated with the 700 SAC has been assigned for unrestricted use by ICs to provide services Predivestiture ATT
34 BOC Not. on the L.EC Networks 1994 SR-TSV-002275 Plan and Dialing Procedures Issue April 1994 NumberIng
Code document Nationwide Numbering Plan Established 700 Service Access SAC code.1 SR-83-1O-076 contains additional information about the 700
service in which the called Telephone numbers within the 800 SAC are used to provide
is for the call Effective 1993 800 party rather than the calling party charged May in the United States Under the interim plan 800 number portability became mandatory to NXX codes were assigned to common carriers Now the 800 NXX codes assigned code carriers U.S entities are placed into database and each NXX can serve multiple in 800 NXX codes assigned to Canadian and non-U.S Caribbean entities are not yet common database with the U.S For these entities 800 NIXX codes are still administered in an 800 number can by NANPA under the interim plan End users interested obtaining 800 Service contact one of the many LECs or ICs that have access to the Management System SMS/800
various services to Telephone numbers within the 900 SAC are used to provide special services callers Information services polling and fund-raising are among the many the 900 service provided Typically these services involve call charges established by in 900 NXX provided to the caller Following industry-approved guidelines outlined 900 codes to Code Assignment Guidelines AL-86-07-006 NANPA assigns NXX common carriers who wish to provide such services to the public.2 list of currently
be in Section 4.9 of the Local assigned 900 NXX codes can found Volume E.cchange Routing Guide LERG TR-EOP-000092.3
about local data The LERG is Beilcore document which contains information routing the obtained from the Routing Database System RDBS This information reflects
for all entities current network configuration and scheduled network changes originating Canada or terminating within the NANP excluding
titled 800/900 NXX Copies of publication Service Access Codes Assignments SR be OPT-001843 which includes the assigned carriers name and telephone number can 201-74O-7500 obtained by calling the Traffic Routing Administrator
Codes 3.3.1 Media Representation of Service Access
The numbers 600700800 and 900 must always be dialed in connection with their should services Whenever these SACs are shown in of media they respective any type for NXX-XXXX or NXX-XXXX not appear in parentheses example 800 900 because parentheses imply that dialing the code is optional Following dialing recommendations made later in this section media advertising that includes 600700
800 or 900 numbers should show them preceded by the prefix digit for example 1800 NXX-XXXX
3-7 BOC Notes on the LEC Networks 1994 SR.TSV-002275 1994 Numbering Plan and Dialing Procedures Issue April
3.4 NI Service Codes
in Service codes serve various special functions Some are no longer in use others are limited use and some are standard almost everywhere Currently service code assignments in many LEC networks are as follows
Table 3-2 Service Code Assignments
Code Assignment
211 Unassigned
311 Unassigned
411 Local Directory Assistance
511 Unassigned
611 Repair Service
711 Unassigned 811 Business Office
911 Emergency
3.4.1 Unassigned Service Codes
Any unassigned service codes including 611 and 811 if they are phased out of service
will be kept available for future assignment by NANPA Service codes may be used notice locally if their assignment and use can be discontinued on short
3.4.2 Universal Emergency Number
service should be Where it has been implemented public emergency universally dial accessible by dialing 911 requirement for callers to or any other
911 is Enhanced 911 service should not be prefix with the digits strongly discouraged that the could referred to or shown as E91 to avoid the possible misconception orshouldbedialed Enhanced 911 servicediffersfrom9ll inthatwithEnhanced9ll
the telephone number and the location address of the caller are available to the
emergency center
3.5 Central Office Codes
in subsections description of Central Office codes is provided the following
3.5.1 Central Office Code Format and Capacity
Since the inception of the NAN Central Office codes have been in the following format
3-8 1994 9l45V.OO2275 DCC Not. an the LEC Networks Plan and Dialing Procedures issue April 1994 NumberIng
NNX
where is any digit through and
is any digit through
Central Office codes for each NPA The addition of This provides capacity of 640 format increases the number of interchangeable Central Office codes in the 0/1 Central Office codes by expanding the format to
NXX and where is an digit 2through
Xis any digit through
Office code combinations to although This increases the potential number of Central 800 described later in this the actual use of some of these codes is not recommended as codes introduced to section Typically interchangeable Central Office are provide As of this about numbering relief and thus delay an impending NPA exhaust printing Office codes 55 NPAs have implemented interchangeable Central
3.5.2 Central Office Code Assignments
within NPA is In general the assignment of Central Office codes geographic with other co-carriers that serve the administered by the predominant LEC in cooperation NPA Each code assignment should be made in accordance with industry-approved
outhned in the Carriers Forum ICCF document guidelines as Industry Compatibility Guidelines 93-0729-0l0 In Central Office Code NNX/NXX Assignment ICCF when an addition the following special codes should be considered making assignment
all NNX/NXX codes Codes for central office assignment should include type Area code NPA codes and excluding the Home Numbering Plan HNPA adjacent the following five codes that currently are reserved for special use
555 Directory Assistance
950 Feature Group Access
958 Local Plant Test
959 Local Plant Test
976 Information Delivery Service
used for Within the 555 code line numbers other than 1212 which are generally could be made available to other entities who want to provide directory assistance business services complementary to directory assistance such as area listings zip 555 code is not the exclusive codes area code service address provision etc. The assistance Line numbers province of any exchange carrier or directory provider be made available to others tariff permitting other than those currently in use should
3-9 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Numbering Plan and Dialing Procedures April
Committee where technically feasible The Industry Numbering INC standing line subcommittee of the ICCF is now working on guidelines for the assignment of
that line number numbers in the 555 code However it is not recommended 555 Further information assignments be made until the guidelines work is completed in the 555 code can be found in OSSGR pertaining to the assignment of local numbers FR-NWT-00027 Operator Services Systems Generic Requirements Section
code 950 can be found in Section 3.9 description of Feature Group access
and to be Codes 958 and 959 are universally assigned as local plant test codes are not
assigned for any other purpose
Service If than Access code 976 is assigned to LECs for Information Delivery more one LEC wishes to use the 976 access code within the same NPA then the LECs mutual involved must resolve muting and billing issues through agreement
3.5.3 Interchangeable Central Office Code Assignment
Central Office codes within an When it becomes necessary to implement interchangeable
NPA the following should be considered
reasonable code assignment order can be established by determining the traffic and the codes in volume from the originating NPA to all other NPAs assigning least-called would order of increasing traffic volume Thus the code for the NPA Office code be the first code assigned as an interchangeable Central Assigning
low traffic volume NPA codes first is an attempt to gradually familiarize callers
with interchangeable Central Office codes
As last resort assign N00 codes
last resort The HNPA Use adjacent NPA codes as Central Office codes only as
code should not be assigned
Nil codes should never be assigned as Central Office codes
Office When assigning 0/1 codes as interchangeable Central codes major for errors that result from caller objective is to minimize the potential dialing might
code is to cause some confusion code that caller frequently uses as an area likely confusion when encountered as Central Office code
3.5.4 Code Conservation and Relief
conservation The continuing growth in telephone number assignments has made code the and code relief an important consideration There are two main factors in increasing in main stations demand for telephone numbers One factor is the traditional increase
is the in services that require due to increasing population The other factor growth new and mobile telecommunications numbers such as Direct Inward Dialing DID Centrex blocks of numbers The DlDlCentrex problem is compounded by the practice of reserving
3-10 Networks SR-TSV-002275 BOC Notes on the LEC 1994 Plan and Procedures Issue April1994 Numbering DIaling
often unknown in addition to working numbers to allow for future growth of an magnitude Services such as cellular telephone and radio paging are creating significant of numbers Code conservation and advance new requirements for large blocks planning for code relief are more critical than ever
Central Office code conservation forestalls the need for NPA code relief Since Central
substantial it is Office code relief for any NPA involves equipment expenditures for minor essential that Central Office codes are not assigned for convenience alone or or
Central Office codes can sometimes be temporary economic advantage Underutilized and recaptured and better utilized Failure to use Central Office codes carefully datesof individual codes efficiently would advance the exhaust NPA
Guidelines5 contains Section of the Central Office Code N1WNXX Assignment conservation measures that the Central Office code administrator should follow in
items that should be making assignments The following list contains additional
considered in any discussion of code conservation measures
for The use of multiple Central Office codes in the same wire center solely rate
determination purposes is discouraged
Central Office codes should not be dedicated to individual DID customers but would be rather shared with other DID or non-DID customers One exception DID
customers whose documented number requirements will approach the
administrative maximum number fill for Central Office code Another would be
non-DID services that require dedicated code to operate
is the of the same Central Office code One application of code sharing assignment increased of station to two or more Central Office entities thereby gaining use thousands numbers in low-fill offices The offices are usually differentiated by the
is limited the costs associated digit of the station number Code sharing use by of automatic with providing required translations additional trunking redesign modification of Automatic rating equipment and coin raters Message Accounting code is AMA equipment and the billing systems Central Office sharing Only involved within the same toll-rate area and practical if the entities are exchange
there are economic benefits to be gained
such caller Special Central Office codes dedicated for miscellaneous purposes as announcement services should be instruction special billing or mass-calling kept
to minimum
The number of Central Office codes dedicated for plant test and official Codes that not suitable for use communications purposes should be minimized are as Central Office codes for example HNPA codes adjacent NPA codes etc codes should be used for telephone company service or as plant test
have been introduced and Once all possible conservation measures interchangeable Central Office codes have been implemented the only recourse for meeting increasing
three available code relief demand is code relief There are NPA measures
3-11 BOC Notes on the LEC Networks 1994 SR-TSV002275 1994 Numbering Plan and Dialing Procsdures issue AprIl
Realign NPA boundaries in multi-NPA states only
Split the existing NPA and introduce new NPA
Overlay new NPA code on the same geographic area as the existing NPA codes
will have Having two or more NPAs assigned to the same geographic area varying effect on administrative procedures and applicable Operations Support Systems OSSs well Analysis is underway to identify any necessary administrative procedural changes as OSSs as the hardware or software modifications that may be required by to implement an
NPA overlay
As of this printing the Industry Numbering Committee INC was working on guidelines for NPA relief planning
3.6 Implementing Interchangeable Codes
As previously mentioned the introduction of interchangeable codes causes changes in the format of both central office codes and NPA codes Table 3-3
Table 3-3 Noninterchangeable/Interchangeable Codes
Type of Format Noninterchangeable Interchangeable NPA Code NO/1X NXX
Central Office Code NNX NXX
The introduction of interchangeable codes provides additional number capacity but
to convert to requires careful plnnning Service providers are expected interchangeable codes as follows
Interchangeable Central Required in an NPA before Office Codes that NPA receives relief
INPA Every service provider must be prepared
Codes to accept and route calls to INPAs after January 1995
3.6.1 Interchangeable Numbering Plan Area Codes
scheduled for The conversion to INPA code capabilities Table 3-4 currently fourfold increase in the completion by January 1995 will provide more than quantity of NPA codes
3-12 Notes the LEC Networks SR-TSV-002275 BOC on 1994 Numb.dng Plan and Dialing Procedures issue April 1994
Table 3-4 Interchangeable NPA Code Conversion
of codes available Maximum quantity NPA 800 using NXX format
Less reserved codes of Nil format
Quantity of NPA codes available for assignment 792
Quantity of NPA codes available for 152 assignment with existing Oil format
Increase in available NPA codes 640
codes be Unlike interchangeable Central Office codes INPA must implemented simultaneously throughout the NANP area Before the first NPA code in NNX format them can be assigned every switching system in the NANP must be converted to accept of as NPA codes The cost of such conversion is largely related to the type switching in For systems involved Dialing procedures will also have to be changed many areas
is after codes are even in areas 10-digit calls dipling required INPA implemented in where interchangeable Central Office codes never existed The same requirements Office to as Section 3.6.2 regarding interchangeable Central codes apply INPA codes well Additional details of the recommended dialing procedures for use with of this section interchangeable codes are shown in Tables 3-8 and 3-9 at the end
Codes 3.6.2 ImplementIng Interchangeable Central Office
codes the The change from Central Office codes to interchangeable Central Office in from 640 792 in the number of available Central format NXX provides an increase to Office codes in an NPA
individual NPA Generally interchangeable Central Office codes are implemented on an in basis without affecting the dialing procedures or switching system arrangements any
takes all other NPA However within the NPA in which the conversion place switching Central Office codes in the format 0/1 as the systems must be modified to accept first digits of 7-digit number
of Also when interchangeable Central Office codes are introduced in an NPA the ability and address the the switching systems to distinguish between 7- 10-digit by examining some other method for making that first address digits received is impaired Thus and are described in the following distinction is required Three possibilities exist
sections
3-13 BOC Note on the L.EC Networks 1994 SA-TSV-00fl75 Issue 1994 Numbering Plan and Dialing Procedures AprIl
3.6.2.1 Prefix Method
The decision The or prefix method is the recommended standard dipling procedure
for the future is based on the to designate the prefix method as the standard following
be dialed This to The prefix method requires that an extra digit must applies 10-digit when numbers calls only and customers already use dialing 10-digit
need for 4-second The prefix method avoids the imposing post-dialing delay benefits scheme on some or all local calls Avoiding this extra delay on local calls
both the telephone companies via reduced holding time for the switching systems common-control equipment and the caller by reducedcall-setup delay
Those areas with Step-by-Step SXS switching equipment will have an additional calls will have to be dialed on 10- penalty under the prefix scheme HNPA toll As the common-control digit basis instead of the 7-digit basis often used now calls will be dialable on the systems replace the SXS equipment all HNPA
recommended 7-digit basis
codes The recommended dialing procedure for use with interchangeable speciftes and 10-digit dialing for all operator-assisted calls both HNPA Foreign Numbering Plan Area FNPA The HNPA call is the one case when even after SXS is than the replaced customers will be asked to dial additional digits other beyond instead of for HNPA their present dialing patterns that is 10-digit 7-digit The additional will avoid the for the 4- operator-assisted calls digitS requirement dialed second thning period that occurs if only digitS are
3.6.2.2 Timing Method
fixed of time The timing method requires that the switching system wait period for
if example approximately seconds after digits have been received to determine arereceivedwithin the additional digits are received If no additional digits required call basis period the switching machine will time out and process the on 7-digit
within few Common Channel Signaling CCS permits connections to be completed continues to seconds after dialing As the long-haul post-dialing delay average decrease calls would the existence of 4- to 6-second delay on an increasing number of local
callers become increasingly irritating to
3.6.2.3 Hybrid Method
toll call is dialed on The hybrid method requires timing only in those cases where
the dialed code is as both Central Office code within 7-digit basis and NXX assigned of the the HNPA and as an NPA code elsewhere in the NANP Successful application of the first hybrid method is dependent on switching systems capable examining digits determine whether these are received after prefix is dialed This is done to digits anNpAcodeonlyanofficecodeonlyoranaflibiguousCOdethatisusedasboth Only
3-14 LEC Networks SR-TSV-002276 BOC Not. on the 1994 Procedures Issue AprIl 1994 Numbering Plan and Dialing
after the seventh to determine if the code is ambiguous is the timing option applied digit is summarized in whether 7- or 10-digit number is being received The hybrid method Table 3-5
Table 3-5 Hybrid Method
Call Dialing Timing Type Procedure Required
Local 7-digit NXX-XXXX No
if is also an Toll 7-digit NXX-XXXX Only NXX
assigned NPA code ambiguous code
No All 10-digit NPA NXX-XXXX
where Common-control switching systems can avoid the need for timing except and central office ambiguous codes that is those codes actually assigned for both NPA the need for However as time and the use exist initially minimizing timing passes of time-out also quantity of ambiguous codes increases the quantity applications all intraNPA increases the number of callers with an ambiguous office code Therefore
calls would eventually be subjected to the timing delay
with In this document references to the prefix or method in connection calls and without to interchangeable codes mean that is used only for 10-digit regard
toll call local call With the method dialing whether the 10-digit call is or prefix 17 situation codes have been digits will result in partial-dial once interchangeable dial are implemented in an NPA Many callers that are presently required to 110 digits The latter will have to be also required to dial 17 digits for 7-digit toll calls procedure of eliminated or the timing or hybrid method implemented prior to implementation be in all interchangeable Central Office codes in an NPA Similar action will required of codes in the NANP NPAs prior to implementation INPA
with codes The recommended dialing procedure for use interchangeable specifies both and calls HNPA calls are 10-digit dialing for HNPA FNPA operator-assisted will be asked to dial additional other than the the single case where customers digits 10 digits instead of 07 digits for beyond their present dialing patterns that is The additional avoids the 4-second timing HNPA operator-assisted calls digits dialed period that occurs if only digits are
caller reaction that results from of change It is difficult to predict the degree of any type
and are factors in smoothing the in dialing procedures Early planning preparation major codes becomes transition process when conversion to interchangeable necessary of it can be to Depending upon the situation and the types equipment involved helpful well in advance of the time when actually implement new dialing procedures they
3-IS BOC Notes on the LEC Networks 1994 SR-TSV-002275
Numbering Plan end Dialing Procedures Issue April 1994
become necessary This practice avoids the introduction of both caller-dialing changes and equipment changes simultaneously when interchangeable codes are implemented
3.7 Telephone Numbers
Routine telephone number assignments are outside the scope of this document such offered However the following are specific considerations for assignments by NANPA
3.7.1 Numbering
with the existence of various Some patterns of diiIing irregularities coupled high-volume numbers for example NPA-555-1212 can lead to large quantities of wrong number calls being directed toward certain station numbers in the Direct Distance Dialing DDD network Wrong numbers due to dialing mistakes when spread randomly through the
receive network are largely unavoidable but tolerable to most customers who an occasional wrong number call However when high-volume numbers are involved even very small dialing error rate can result in significant volume of wrong numbers situation be intolerable the being directed to few customers Such can to recipients
Therefore it is appropriate to take steps to avoid such situations
The following are some of the known dialing irregularities
Dialing that starts before dial tone is received results in the loss of Dual-Tone
Multifrequency DTMF dialed digits or the first few pulses digits of dial-
pulsed rotary dialed call Slow dial tone aggravates this irregularity
Omitting the prefix digit in 10-digit call where the interchangeable Central
Office codes are in use
call address This Dialing one digit too high or too low anywhere inthe is
generally more prevalent with rotary dials than with touch-tone dialing
Omitting the 800 SAC when customers know that the called 800 number is in their own NPA
To avoid problems resulting from these irregularities the following guidelines are recommended
the format in NPAs not using 10-digit-only dialing any Central Office using
NX5-XXXX should leave the number NX5-5512 unassigned or for internal purposes leave 0/1 only NPAs with interchangeable Central Office codes should 5-55 12
unassigned This prevents error
In NPAs using interchangeable Central Office codes any Central Office using the
format 0/1 X-XXXX should leave the number 0/1 X-5551 or preferably This N0/1X-555X unassigned or use it for internal purposes only prevents error
3-16 SH-TSV-002275 BOC Not. on th LEC Networks 1994 Plan and Procedures Issu AprIl 1994 NumberIng DIaIkg
Any central office using codes 255 355 or 455 should leave station number 1212
unassigned This is to guard against error in the rotary dial case The assumption
is that once caller places finger in the wrong position on the dial he/she will dial
all three Central Office code digits without removing the dialing finger each time
Similar logic could be applied to 222- 444- 666- and 888-1212 for touch-tone
dialing but such errors seem less prevalent than the rotary dial case
Any central office using code in the form N91 should avoid placing subscribers who station number are likely to receive high volume of calls in the N91-1XXX to
prevent misdialing to 911 This prevents error
3.7.2 Coin Station Numbering
It has been recommended that public and semipublic stations be assigned line numbers in
the 9000 series for example NXX-9XXX Generally present operating practices
include check for public/semipublic telephones on collect or third-number calls to 9000
series numbers only
Many public/semipublic telephones meet the requirements for an automated check In those cases where the automated public/semipublic station check can be applied there is
no need to have the called public station numbered in the 9XXX series
However there are still many situations in which the 9XXX line number is the only
indication of public/semipublic station Therefore it is still suggested that companies
assign public/semipublic stations in this 9XXX line number series when possible
3.8 Dialing Procedures
to Dialing refers to the use of certain digits or special characters as prefixes or appendices
the number address defined by the NANP or its equivalent elsewhere in the world
3.8.1 Recommended Dialing Procedures
for IC and The preferred dialing format excluding any procedures required selection
is summarized as after all switching systems throughout the NANP are common control follows
and digits All local station calls
all direct-dialed toll calls within the HNPA
All toll local station calls 110 digits FNPA or
0l0digits AllHNPAandFNPAcallsthat
are customer dialed and
operator assisted
3-17 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Numbering Plan and Dialing Procedures issue April 1994
The following set of principles were used in developing the recommended dialing procedures
Dialing procedures should
Be simple and easy to understand by end users
Require dialing minimum number of digits
in for Provide continuity dialing procedures the long term
Give the end users minimum number of different dialing procedures to reach
local and toll points
Involve minimumnumber of boundaries which affect dialing procedures
Provide uniform dialing procedures for all customers to reach all local and toll
points This applies also to optional Extended-Area Service EAS when calls to the same point may be local for some customers and toll for others
Provide maximum possible protection to prevent misdialed local calls from
completing to toll point
Be arranged to minimize customer number changes both short and long term
Result in as few changes as possible in existing dialing procedures
10 Provide for uniform local dialing procedures between NPAs in multi-NPA EAS
situations where there is close community of interest and mobility across the NPA boundary
3.8.2 Dialing Procedure Objectives
It would be ideal to have identical dialing procedures in all areas However with the current differences in switching system capabilities it is almost certain that variety of
for time It is recommended dialing procedures will remain in use some to come that whenever an opportunity arises steps be taken to move toward the ultimate dialing plan
Tables 3-6 and 3-7 show the recommended dialing procedures for areas with and without
SXS equipment respectively
There are several points about the recommendations that should be emphasized
The 11OD HNPA or prefix dialing procedure can exist without interchangeable
codes but interchangeable codes cannot exist without dialing unless timing is invoked
There is difference between the seven digits dialing procedures that presently
of the and the recommended when exist in many parts country procedure interchangeable codes are implemented In its most common present usage the
implies toll calls as well as all 10-digit calls When used with interchangeable
codes the implies 10-digit so it must not be used with 7-digit calls unless the
hybrid method of dialing or timing is implemented
3-18 1994 SR-TSV002275 BOC Notes on the LEC Networks Plan and Procedures issue AprIl 1994 NumberIng Dialing
that is Any LEC that might choose to implement the long-term dialing procedures of codes is for 10-digit only prior to implementation interchangeable the recommended encouraged to do so The intent is not to imply that codes are procedures should be deliberately delayed until interchangeable in implemented There would seem however to be significant advantage having to to the long-term di1ing procedures running smoothly prior changeover
interchangeable codes
Any LEC that now uses 10-digit dialing with or without 7-digit dialing
if should not revert to 10-digit dialing even equipment changes for example Movement elimination of SXS equipment would otherwise allow them to do so and in the future is in the direction of 10-digit to be dialable everywhere any
is to cause customer confusion change away from that objective only likely
3.9 Dialing Prefixes for Carrier Selection
and As result of the Modification of Final Judgment MFJ the GTE consent decree
in well federal the implementation of access change plans state as as jurisdictions many boundaries ICs connect callers are required to select an IC for calls that cross LATA and LEC networks using several their facilities to Bell Operating Company BOC many Feature different access arrangements The most common access arrangements are Group FGB and Feature Group FGD
FGB callers reach an ICs facility by dialing 950-XXXX The XXXX digits expanded called from 0/1XXX effective April 1993 in the 950 number identify the IC and are
are NANPA in accordance with the Carrier Identification Code CIC CICs assigned by ICCF 92-0726-002 industry-approved guidelines CCAdninistrative Guidelines second dial tone When the call is cut through the IC switching equipment provides Personal Identification Number the indicating that the caller must dial PIN plus
number to be called
IC on basis If the FGD permits callers to presubscribe to or select specific per-call the called number need be dialed caller wants to use the presubscribed carrier only basis and choose an FGD also allows the caller to override presubscription on per-call 10 The is called the alternate IC by dialing 1OXXX 0/1 digits 1OXXX dialing prefix CAC the Carrier Access Code CAC The last digits of the 1OXXX are CIC
than ICs Due to the FGB and FGD access are available for certain uses to entities other the of FGB CICs has required expansion popularity of these access arrangements supply exhaust in 1995 and that of FGD is projected to early
shown below FGD CICs are planned to be expanded to the dialing pattern
1O1XXXX Oil 10 digitS
3-19 BOC Notes on th LEC Networks 1994 SR-TSV.002275 Issue 1994 Numbering Plan and Dialing Proc.durss April
shown in Tables Additional details of dialing procedures available for use with FGD are in Feature 3-8 through 3-10 Further information pertaining to FGB access can be found Group FSD 20-24-0300 TR-TSY-000698.8 FGD access information can be found in
Compatibility Information for Feature Group Switched Access Service TR-NPL
000258 and Expansion of Carrier Identification Code Capacity for Feature Group FGD TR-NWT-001050.10
3.10 Operator Assistance
Callers reach the LEC operator by dialing zero To reach-the presubscribed
is available interexchange operator carrier 00 zero zero dialed where presubscribed customer should also be able to dial 1OXXX to reach an alternate IC operator
end 00 can be muted either to the LEC facility In nonequal-access offices operator facility to single ICs operator facility or it can be blocked
3.11 International Direct Distance Dialing
There are three major types of carriers involved in international calling
and International Carriers INCs transport the call between United States gateway
foreign country where the INC connects to the applicable foreign telephone entity
call from the to the Interexchange Carriers iCs provide transport originating LATA INC gateway office
Jnterexchangellnternational Carriers IC/INCs provide both domestic interLATA
transport and international transport
On most international calls both ICs and INCs axe involved which implies that two carriers are selected by single CAC
and international and single carrier IC/INC provides both interLATA transport
uses single CAC that includes both
to handle each others traffic An IC and an INC having separate CACs can agree call could customer placing an International Direct Distance Dialing IDDD use the IC and the either carriers CAC The interLATA portion would be handled by
international portion would be handled by the NC
An IDDD caller is not able to independently specify both an IC and an INC for an the caller international call Except in the case of carrier that provides both functions will specify either the IC or INC of choice The other carrier INC or IC respectively involved will be the result of prearranged business agreement
3-20 SR-TSV-002275 BOC Notse on the LEC Networks 1994 Plan and Procedures issue April 1994 Numbering Dialing
the local When an international call is dialed by customer in national network international address switching system must be able to recognize that it is receiving an
is alerted to the fact that an In the NANP local switching system with IDDD capability The international number is being dialed by use of special prefix code following
for in the dialing patterns are utilized IDDD NANP
calls 011 code national number For station-paid direct-dialed country
code national number For operator-assisted calls 01 country
be found in Section 1.10 of the The list of current country code assignments can LERG.11
3.12 OXCand 1XX Codes
codes and that are not Within the NAN there are two series of 3-digit OXX 1XX End used as NPA or Central Office codes but are used for various specialized purposes offices offices or their associated Centralized Automatic Message Accounting CAMA OXX 1XX code in the NPA or will not accept 7-digit or 10-digit address having or Central Office code field However such codes are accepted and muted by switching
received via an intermachine tnink source authorized to generate them systems when or for example testboanl In the past OXX codes were typically used as pseudo- calls office that did not have normal Central Office code to route special to switching codes also used to Central Office code assigned for example toll office These were office termination that LEC did not want dialed using route special calls to switching
normal address When OXX codes serve pseudo-Central Office code function they the be in each are used in conjunction with an NPA code so most of codes can reused NPA
used codes For some By contrast 1XX codes are frequently as pseudo-NPA example codes in the form 18X are used to direct international calls to the proper gateway office
does administer or the uses of the Beilcore in its role as NANP Administrator not assign be used for OXX or 1XX codes The selection of the specific OXX or 1XX code to of the carrier its use If the routing or billing function is the responsibility implementing OXXorlxXcodewillbeusedtOrOUtecallsbetweeflaLECandanlCthecode The selection should be made by mutual agreement to avoid code conflicts NAN code Administrator will act as coordinator if requested in the selection of OXX or lxx
of the lists the that will be used in the networks of two or more ICs Section 1.4 LERG
1XX codes that have universal muting assignments.11
3-21 BOC Notes on the LEC Networks 1994 SR-TSV002275
Numbering Plan and Dialing Procdurss Issue AprIl 1994
3.13 SpecIal Characters and
need to The advent of new services and special dialing procedures creates an increasing make use of the and characters for special functions
To minimize the amount of confusion experienced by callers using these characters there is an effort to standardize their use It is also important that consistent terminology be be called known and used when referring to these characters The and the should
the The terms number and star have been the number sign and star respectively sign of the asterisk for and for internationally agreed upon Use term pound sign should not be used in documentation dealing with dialing procedures
At present the characters and have the following general applications
the The first use of the number sign is as an end-of-dialing or conclude present
action and proceed to the next action indicator This end-of-dialing use exists
today and avoids timing period for example IDDD using certain types of
switching systems The conclude-and-proceed use also occurs in some telephone
call is credit card services where the customer wants to indicate that the present
over and new call is about to be placed for example sequence calling The
latter use is expected to become more common as services with extended dialing
sequences become more prevalent
The second use of the number sign is as the first character when dialing call of that is wideband or other data call requiring special treatment In certain types
data calls both an initial and concluding may be required Functionally this is
similar in many respects to the KP address ST format used by operators
The first use of the star is as prefix when dialing Vertical Service Code VSC for example call forwarding of the form XX In this application the certain desired indicates to the switching system that the digits following specify feature/service Section 3.14 discusses VSCs
The second major use planned for the is not yet implemented It is anticipated of various that new services will require customer dialing digit strings on
sequential basis in response to prompting The is expected to provide an error-
correcting function for such dialing sequences Most caller-recognized dialing and errors in existing services are corrected by the customer simply hanging up be in future situations The will starting over That will not appropriate some
allow the caller to back up to some preestablished point and redial only the segment in which an error was recognized
does Prefix 11 provides the same function for dial-pulse rotary dial telephones that for DTMF touch-tone telephones
3-22 the LEC Networks 1994 SR-TSV-002275 BOC Notes on Plan and Procedures Issue AprIl 1994 NumberIng Dialing
3.14 VertIcal Service Codes
Vertical Service Codes VSCs are customer-dialed codes in the XX dialing format for used to touch-tone phones and 1XX dialing format for rotary phones They are provide customer access to features and services for example Call Forwarding Automatic such LECs and ICs For Callback etc provided by network service providers as activated 72 or 1172 example call forwarding is by dialing
enable consistent the VSCs are assigned to features or services to accessibility throughout of common/standard VSCs is Public Switched Telephone Network PSTN The purpose service for to minimize customer confusion and provide standard access approach
features and services within
Multiple individual networks multi-network applications
Across and/or among two or more networks on an internetwork basis internetwork in consistent applications where multiple networks must act upon VSC manner
on given call
but multi-networks and VSC assignments are to be made using the same VSC resource will be identified internetwork applications separately
VSCs are assigned and administered by NANPA using industry-approved guidelines ICCF 92-1127-005 Vertical Service Codes Assignment Guidelines provides information of code and code on assignment principles and criteria responsibilities applicants
administrator and code application procedures.12
LERG.11 Current VSC assignments can be found in Section 1.6 of the
3.15 SS7 Point Codes
to each SS7 network Signaling System SS7 point codes are unique numbers assigned SS7 code consists of three 8- node that are the name and address of that node The point and Cluster Member bit binary octets known as the Network ID Cluster Code values of 00000000 to 11111111 respectively Each octet has possible assignment
translating to to 255
the Alliance for Telecommunications Industry NANPA using guidelines established by Solutions ATIS Subcommittee T1S1.3 assigns the following
defined those networks at least 75 Signaling To large networks currently as having and 150 in and also having Signaling Transfer Point Points SPs initially years the Network ID The network SIP or SiP functionality NANPA assigns large
Standards Association Formerly the Exchange Carriers ECSA
3-23 BOC Notes on the LEC Networks 1994 SR-TSV.002275 NumberIng Plan and Dialing Procedures Issue April 1994
administrator assigns the Cluster Codes and Cluster Members to the SPs within the
large network
To small networks currently defined as those networks having less than 75 SPs
initially and less than 150 in years and also having an SW or SiP functionality
NANPA assigns the Network ID and Cluster Codes The small network within the network administrator assigns the Cluster Members to the SPs small
Those companies without SW functionality are grouped together and share
Network ID and Cluster Codes NANPA assigns the Network ID Cluster Codes
and Cluster Members to the SPs
3.16 AutomatIc Number identification ii Digit Assignments
Automatic Number Identification ANT IF digits are two digits that are sent with the
originating telephone number identifying the type of originating station for example Plain Old Telephone Service Hotel/Motel etc. Assignment of new
II made is ANT digit pairs are through industry consensus at ICCF NANPA responsible for tracking the assignments Listings of ANT II digit pairs can be found in Section 1.8 of the LERG.1
3-24 BOC Notes on the LEC Networks 1994 SR-TSV-002215 Numbering Plan and DialIng Procedures Issue AprIl 1994
with SXS Table 3-6 Recommended Dialing Procedures for Locations Equipment
Without With
Interchangeable CO Codes Interchangeable CO Codes
Pre- Area CO Pre- Area CO
Code Use Fix Codet Code Use Type of CaH Fix Code NXX-XXXX Local Direct- NNX-XXXX NXX-XXXX NR Dialed NNX-XXXX NR NR HNPA NW NNX-XXQC NR cvi NXX-XOcX NW NNX-XOCX NWIX NXX-XXXX NXX-CCXX FNPA Codes NNX-XXXX NNX-XXXX NR NXX-XXXX NR NW NNX-OcXX NR Wi NXX-XXXX NR NW1 NNX-OCXX NWI NXX-XXXX NXX-XXXX NR FNPA Codes NW NNX-XXXX NR Wi W1X NNX-XXXX NW1 NXX-OOCX NXX-XXXX NR Toil Direct- NNX-XXXX NXX-OOCX NR Dialed NNX-XXXX NR HNPA W1X NNX-XXXX NR Wi NXX-OOcX NR NWIX NNX-000C NW1X NOC-CCOC FNPA NW NNX-OOCC NR Qf NXX-OCOC NR Wi NNX-OCCX WI WCC-XXXX NNX-XXXX NOc-OOcX NR All Operator- Assisted NNX-XOOC NW NCC-000C HNPA NNX-XXXX NCC-OOOC NR FNPA Codes NWXNNX-XXOcP NW1XNXX-OOCXR WI NXX-OCXX FNPA Codes NW NNX-OOCC
Permissive Digit or procedure CO Central Office permitted in addition to recommended FNPA Foreign Numbering Plan Area procedure HNPA Home Numbering Plan Area Recommended procedure SXS Any digit through Step-by-Step NR Procedure not recommended Any digit through
to an IC interLATA calls In locations where FGD has been implemented if the caller is not presubscrlbed form 1OXXX the dialing format shown in this table require use of CAC currently in the preceding Central Office codes in those NPAs using interchangeable Unless timing is used in addition to being required is for all areas They will also be required unless timing these procedures are the recommended objectives in the NANP used in all areas when INPA codes are implemented codes In this the NPA code format also will These iilauug procedures will also apply for INPA case become NXX versus Wi
3-25 BOC Notes on the LEC Ntworks 1994 SR-TSV-002275 Issue 1994 Numbering Plan and Dialing Procedures April
SXS Table 3-7 Recommended Dialing Procedures for Locations without Equipment
Without Wi
Interchangeable CO Codes Interchangeable CO Codes
Pre- Area CO Pre- Ares CO
Type of Call Fix Code Code Use Fix Codel Code Use
Local Direct- NNX-XXXX NO-OOOC Rt
Dialed NNX-XXXX NR NOC-XXXX NR NR HNPA af NNX-XOOC NR NW NOC-OOOC NGIIX NNX-XOCC NWIX NO-000
FNPA Protected Codes NNX-XOCX NoC-OCXX NNX-XOO NR NOC.XOcX NR
Gil NNX-OCC NR NW NOC-XXJOC NR NW1X NNX-XCOC NW NXX-CCXX
NR Gil NXX-OOCX NR FNPA Nonprotected Codes Gil NNX-XOCX WIX NNX-XOOC NW NXX-CCXX
Toll-Direct NNX-XXXX NXX-XXXX
Dialed NNX-XXXX NR NOC-XCOC NR JPA W1X NNX-XXXX NR WI NOC-COC NR NW NNX-XOCC NW NOC-OOcX
FNPA Gil NNX-XXXX Gil N30C-000C NR NW NNX-XXXX Gil NOC-XOOC R4 NXX-000 NR All-Operator NNX-XXXX
AssLrftd Gil NNX-XXXX NW NOC-COCC Rf UNPA NOC-XXXX NR FNPA Protected Codes NNX-XXXX NW1XNNX-XXXXP NG1XNXX-XXXXR
FNPA Nonprotected Codes Gil NNX-OOOC NW NOC-XXXX
Legend
cwi DigitOorl Permissive procedure
Co Central Office be permitted in addition to
FNPA Foreign Numbering Plan Area recommended procedure
HNPA Home Numbering Plan Area Recommended procedure SXS Any digit through Step-by-Step NR Procedure not recommended AnydigitOthrough9-
to an interLATA calls jrr P1I been implemented ffl caller is not presubscribed IC the fornmt shown in this table require use of CAC currently in the form 1OXXX preceding dialing NPAs Central Office codes Unless timing is use in addition to being required in those using interchangeable will also be unless timing is these procedures are the recommended objectives for all arees They required the NANP used in all aress when INPA codes are implemented in format also wifi These MIlng procedures will also apply for INPA codes In this cue the NPA cede become NXX versus Wi codes become These are the recommended long-term procedures to apply after SXS equipment and protected
obsolete
3-26 SR-TSV-002275 BOC Not. on the LEC Networks 1994 and Procedures Issue AprIl Numbrlng Plan Dialing
Table 3-8 Recommended Dialing Procedure for Directory Assistance Under Feature Group
Type of Dialing Operator Call Procedure Reached
IntraLATA
HNPA 411 or555-1212 LEC FNPA 1NPA-555-1212 LEC
current HNPA 1OXXX-555-1212 IntraLATA Carrier FNPA55 1OXXX-1NPA-555-1212 IntraLATA Carrier
Planned HNPA5 1O1XXXX-555-1212 IniraLATA Carrier FNPA 1O1XXXX-1NPA-555-1212 IntraLATA Carrier
InterLATA
HNPA5 555-1212 LEC
FNPA 1NPA-555-1212 ICt
current HNPA 1OXXX-555-1212 ICt FNPA 1OXXX-1NPA-555-1212 ICt
Planned
HNPA 1O1XXXX-555-1212 ICt FNPA 1O1XXXX-1NPA-555-1212 ICt
FNPA Foreign Numbering Plan Area HNPA Home Numbering Plan Area
IC Inteiexchange Carrier LATA Local Access and Transport Area
LEC Local Exchange Carrier NPA Numbering Plan Area
Usc of the prefix is acceptable in areas where CAMA access is required allowed oniy applies in those areas where intraLATA competition is
calls The call will be banded off to the IC but the IC Piesubsctiption applies to interLATA directosy assistance
assistance result in LEC business arrangement with LEC to provide directosy may reaching operator
3-27 SR-TSV-002275 BOC Notes on the L.EC Networks 1994 Issue 1994 Numbering Plan and Dialing Procedures AprIl
Offices Table 3-9 Treatment of And 00 Dialed Calls from Equal-Access End
Dialing Suggested Disposition Format Equal-Access End Office
LEC
00 ICS
Current 1OXXX.0 IC Planned 1O1XXXX0 IC
Current 1OXXX00 IC Planned 1O1XXXX00 IC
Current 1OXXX 7/1OD IntraLATA IC if permittedt
Planned 1O1XXXX O-i7110D IntraLATA IC if permittedt
O7110D IntraLATA-LEC IntraLATA ICI
Legend IC Interexchange Carrier
LATA Local Access and Transport Area LEC Local Exchange Carrier AnydigitOthrough9 Digits
Assumes subscriber is presubscribed 1OXXX While this is not an NANP dialing standard to avoid customer confusion 00 the IC dialed calls should be processed and routed to operator facility
varies this section does Because regulatory treatment of IntraLATA competition widely
dialed 7/1OD where such is allowed not specifically address competition 007/10Dandl0XXXO07/10DdialedcallSenOtdefifledmtheN Upon
be routed to the IC facility completion of dialing 00 the call would generally operator This to subscribers with and subsequent digits would be acknowledged may only apply
dial customers not be DTMF telephones calls of this type generated by rotary may proccsse
3-28 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Plan and Dialing Procedures Issue April 1994 Numbering
Available with Feature Table 3-10 Dialing Procedures Group
Destination Dialing Format
Carrier 1OXXX 1OXXX NPA NXX XXXX specified by 1OXXX 011 CC NN
carrier 011 CC NN Pscribed
carrier function 01 CC NN Presubscribed operator
NPA NXX XXXX InterLATA Presubscribed carrier NPA NXX XXXX IntraLATA LEC function NPA NXX XXXX InterLATA Presubscribed carrier operator LEC function NPA NXX XXXX IntraLATA operator
of 1OXXX NPA NXX XXXX Operator function 1OXXX 1OXXX 01 CC NN carrier specified by
LEC operator
carrier function 00 Presubscnbed operator
1OXXX Operator of carrier specified by 1OXXX
SAC NXX XXXX Carrier determined by 6-digit or 10-digit
translation of SAC NXX
1OXXX IOXXX Wi SAC NXX XXX Carrier specified by
1OXXX Carrier specified by 1OXXX
Legend Wi Digitoorl
CC Country Code Any digit2through9 NPA Numbering Plan Area Anydigit0through9
to CXXX CIC in 1995 Conversion planned to 1OXXXX dialing prefix XXX expansion
indicates optional di1ing digits touch-tone at the end of an indicates that diAling the character on DTMF telephones
If it eliminates the need for timing in some international address is desirable but not required used
cases
CAC is indicates that the character as the end of dialed required
3-29 BOC Notes on the L.EC Networks 1994 SR-TSV-002275 issue April 1994 Numbering Plan and Dialing Procedures
Table 3-il NPA Codes in Alphabetical Order as of February 1994
STATE/PROVINCE STATE/PROVINCE STATE/PROVINCE OR OTHER AREA OR OTHER AREA OR OTHER AREA SPECIAL USE CODE SPECIAL USE CODE SPECIAL USE CODE
800 Service 800 Iowa 515 Nova Scotia 902
900 Service 900 Iowa 712 Ohio 216
Alabama 205 Kansas 316 Ohio 419
Alabama 334 Kansas 913 Ohio 513 614 Alaska 907 Kentucky 502 Ohio 405 Alberta 403 Kentucky 606 Oklahoma Arizona 520 Louisiana 318 Oklahoma 918
Arizona 602 Louisiana 504 Ontario 416 519 Arkansas 501 Maine 207 Ontario Caribbean Islands 809 Manitoba 204 Ontario 613 705 British Columbia 604 Maryland 301 Ontario California 209 Maryland 410 Ontario 807
California 213 Massachusetts 413 Ontario 905
California 310 Massachusetts 508 Oregon 503
California 408 Massachusetts 617 Pennsylvania 215
California 415 Michigan 313 Pennsylvania 412
California 510 Michigan 517 Pennsylvania 610
California 619 Michigan 616 Pennsylvania 717
California 707 Michigan 810 Pennsylvania 814
California 714 Michigan 906 Quebec 418
California 805 Minnesota 218 Quebec 514
California 818 MInnesota 507 Quebec 819
California 909 Minnesota 612 Rhode Island 401
California 916 Mississippi 601 Saskatchewan 306 Canada Services 600 Missouri 314 South Carolina 803
Colorado 303 MIssouri 417 South Dakota 605
Colorado 719 MIssouri 816 Tennessee 615
Connecticut 203 Montana 406 Tennessee 901
Delaware 302 Nebraska 308 Texas 210
Dist of Columbia 202 Nebraska 402 Texas 214
Florida 305 Nevada 702 Texas 409
florida 407 New Brunswick 506 Texas 512 Texas 713 Florida 813 New Hampshire 603 Florida 904 New Jersey 201 Texas 806 817 Georgia 404 New Jersey 609 Texas 908 Texas 903 Georgia 706 New Jersey 505 Texas 915 Georgia 912 New Mexico 710 Hawaii 808 New York 212 U.S Govenusent 801 IC Services 700 New York 315 Utah 802 International Inbound 456 New York 516 Vermont 703 Idaho 208 New York 518 Virginia 607 804 illinois 217 New York Virginia 206 illinois 309 New York 716 Washington 718 360 Illinois 312 New York Washington 914 509 Illinois 618 New York Washington 304 Illinois 708 New York 917 West Virginia Wisconsin 414 Illinois 815 Newfoundland 709
Indiana 219 North Carolina 704 Wisconsin 608 715 Indiana 317 North Carolina 910 Wisconsin 307 IndiRnR 812 NOrth Carolina 919 Wyoming Iowa 319 North Dakota 701
3-30 SR-TSV-002275 BOC Not. on the LEC Networks 1994 Plan and Dialing Procedures issue AprIl 1994 NumberIng
Table 3-12 NPA Codes in Numerical Order as of February 1994
STATE/PROVINCE STATE/PROVINCE STATE/PROVINCE AREA OR OTHER AREA OR OTHER AREA OR OTHER CODE SPECIAL USE CODE SPECIAL USE CODE SPECIAL USE
201 New Jersey 415 California 707 California 202 Din of Columbia 416 Ontario 708 illinois 203 Connecticut 417 Missouri 709 Newfoundland Government 204 Manitoba 418 Quebec 710 U.S
205 Alabama 419 Ohio 712 Iowa 206 Washington 456 International Inbound 713 Texas 207 Maine 501 Arkansas 714 California 208 Idaho 502 Kentucky 715 Wisconsin
209 California 503 Orogon 716 New York
210 Texas 504 Louisiana 717 Pennsylvania 212 New York 505 New Mexico 718 New York 213 California 506 New BrunSWiCk 719 Colorado
214 Texas 507 Minnesota 800 800 Service Massachusetts 801 Utah 215 Pennsylvania 508 216 Ohio 509 Washington 802 Vermont
217 illinois 510 California 803 SOUth Carolina
218 Minnesota 512 Texas 804 Virginia
219 Indiana 513 Ohio 805 California
301 Maryland 514 Quebec 806 Texas Ontario 302 Delaware 515 Iowa $07 Hawaii 303 Colorado 516 New York 808 809 Caribbean Islands 304 West Virginia 517 Michigan 305 Florida 518 New York 810 Michigan 306 Saskatchewan 519 Ontario 812 Indiana 307 Wyoming 520 Arizona 813 Florida 308 Nebraska 600 Canada Services 814 Pennsylvania illinois 309 Illinois 601 Mississippi 815 Missouri 310 California 602 Arizona 816 Texas 312 Illinois 603 New Hampshire 817 California 313 Michigan 604 British Columbia 818 314 Missouri 605 South Dakota 819 Quebec 315 New York 606 Kentucky 900 900 Service
316 Kansas 607 New York 901 Tennessee 317 lndiRn2 608 Wisconsin 902 Nova Scotia
318 Louisiana 609 New Jersey 903 Texas
319 Iowa 610 Pennsylvania 904 Florida 905 Ontario 334 Alabama 612 Minnesota 906 360 Washington 613 Ontario Michigan 401 Rhodelsland 614 Ohio 907 Alaska
402 Nebraska 615 Tennessee 908 New Jersey California 403 Alberta 616 Michigan 909 Massachusetts 910 North Carolina 404 Georgia 617 405 Oklahoma 618 illinois 912 Georgia 406 Montana 619 California 913 Kansas New York 407 florida 700 IC Services 914 Texas 408 California 701 North Dakota 915 916 California 409 Texas 702 Nevada 917 New York 410 Maryland 703 Virginia 918 Oklahoma 412 Pennsylvania 704 North Carolina 919 North Carolina 413 Massachusetts 705 Ontario 414 Wisconsin 706 Georgia
3-31 SOC Notes on the LEC Networks 1994 SR-TSVMO2215 Issue 1994 Numbering Plan and Dialing Procedures April
3-32 LEC Networks SR-TSV-002275 BOC Notes on the 1994 Pten and Procedures Issue AprIl 1994 NumberIng DIaling
Ref erences
SR-83-1O-076 Nationwide Numbering Plan Established 700 Service Access Code SAC October 1983
AL-86-07-006 900 NXX Code Assignment Guidelines Issue Beilcore July 1986
TR-EOP-000092 Local Exchange Routing Guide LERG Volume Offshore
and International 800 Series LATAs Independents 900 Series LATAs Beilcore March 1994
SR-OPT-001843 Service Access Codes 800900 NXX Assignments Issue Beilcore December 1993
Guidelines ICCF 93-0729-010 Central Office Code NNX/NXX Assignment
Industry Carriers Compatibility Forum 1993
FR-NWT-00027 OSSGR Operator Services Systems Generic Requirements Bellcore 1994 Edition
ICCF 92-0726-002 CICAdministrative Guidelines Industry Carriers
Compatibility Forum 1992
TR-TSY-000698 Feature Group FSD 20-24-0300 Issue Beilcore June 1990 module of LSSGR FR-NWT-000064 1989 plus Revision July
Switched Access TR-NPL-000258 Compatibility Information for Feature Group Service Issue Beilcore October 1985
10 TR-NWT-001050 Expansion of Carrier Identification Code CIC Capacity for Feature Group FGD Issue Beilcore April 1991
Guide 11 TR-EOP-000085 through TR-EOP-000092 Local Exchange Routing LERG volumes Beilcore March 1994
12 ICCF 92-1127-005 Vertical Service Codes Assignment Guidelines Industry
Carriers Compatibility Forum 1992
3-33 BOC Notes on the LEC Networks 1994 SR-TSV..002275 Issue 1994 Numbering Plan and Dialing Procedures AprIl
NOTE
All Beilcore documents are subject to change and their citation in this document reflects the most current information available at the time of this printing Readers are advised to check current status and availability of all documents
To obtain Beilcore documents contact
Belicore Customer Relations
Corporate Place Room 3A-184
Piscataway NJ 08854-4156 l-80052l-CORE
908 699-5800 for foreign calls
and Beilcore BCC personnel should contact their company document coordinator
personnel should call 908 699-5802 to obtain documents
be obtained the Industry Carriers Compatibility Forum ICCF documents can through
Alliance for Telecommunications Industry Solutions ATIS formerly the Exchange
Carriers Standards Association by calling 202 628-6380
3-34 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Plan and Dialing Procedures Issue AprIl 1994 Numbering
Bibliography
Guidelines ICCF 93-0729-0 10 Industry Central Office Code NNX/NXX Assignment
Carriers Compatibility Forum 1993
Carriers CICAdministrative Guidelines ICCF 92-0726-002 Industry Compatibility Forum 1992
Access Service TR-NPL Compatibility Information for Feature Group Switched
000258 Beilcore Piscataway NJ October 1985
Feature Expansion of Carrier Idenhficanon Code CIC Capacity for Group FGD
TR-NWF-001050 Beilcore Piscataway NJ April 1991
NJ June Feature Group FSD 20-24-0300 TR-TSY-000698 Beilcore Piscataway 1989
TR-EOP-000085 TR-EOP Local Exchange Routing Guide LERG volumes through 000092 Bellcore Piscataway NJ March 1994
Code Nationwide Numbering Plan Established 700 Service Access SAC SR-83-10-076 October 1983 NJ 900 NXX Code Assignment Guidelines AL-86-07-006 Belicore Piscataway July 1986
FR-NWT-00027 Bellcore OSSGR Operator Services Systems Generic Requirements Piscataway NJ 1994 Edition
Service Access Codes 800/900 NXX Assignments SR-OPT-001843 Beilcore Piscataway NJ December 1993
TA-TAP-000459 Beilcore Ten-Digit 800 Service Number Administration Guidelines
Piscataway NJ August 1987
92-1127-005 Carriers Vertical Service Codes Assignment Guidelines ICCF Industry
Compatibility Forum 1992
3-35 BOG Not. on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Numbering Plan and Dialing Procedures AprIl
3-38
BOC Notes on the LEC Networks 1994 SR-TSV-002275 Contents Issue AprIl 1994
SectIon Network Design and Configuration Contents
4-1 Network Design and Configuration
4.1 Introduction
.. 4i 4.1.1 TeriTlinal Equipment ...... 43 4.1.2 Network Configurations 44 4.1.3 Ssvitcb.i.ng Eqiipmnent 4-5 4.1.3.1 End Office Switching Systems 45 4.1.3.2 HostfRemote Switching Unit 4-6 4.1.3.3 Tandem Switching Systems 4-8 4.1.3.4 Dynamic Routing Switching Systems 4-8 4.1.3.5 Combined Systems 4-8 4.1.3.6 Digit Utilization and Translation
4.1.3.7 Trunk Circuits 49 4-10 4.1.3.8 Call Control 4-10 4.1.4 Interexchange Carrier Points of Presence 410 4.2 Operator Services Systems 41 4.2.1 Existing Architecture 4-11 4.2.2 Future Architecture 4-13 4.2.3 OSS Switching Environment 4-13 4.2.4 Position in the Network 4-13 4.2.5 Call Handling 4-13 4.2.6 OSS Subsystems. 414 4.2.7 Features...... 4-14 4.2.7.1 Basic OSS Features 4-15 4.2.7.2 Customer Access Features 4-15 4.2.7.3 Customer Listing Information Features
Call Features 4-16 4.2.7.4 Service Specific Handling 4-16 4.2.7.5 Special Billing Features...... _...... 4-16 4.2.8 Teleconirnunications Relay Service 4-17 4.3 Network Design Considerations 4-18 4.3.1 Fundamentals of Hierarchical Routing 4-21 4.3.2 Application of Alternate Routing 4-22 4.3.3 Fundamentals of Dynamic Routing Technique 424 4.4 Blocking Probabilities .... 425 4.5 LATA Network Configurations.. 4-25 4.5.1 IntraLATA Configurations 426 4.5.1.1 Routing ...... 426 4.5.1.2 Blocking 426 4.5.1.3 onflgurations 4-30 4.5.2 Dynamic Routing Configuration
... 431 4.5.3 LATAAccess Configurations ...... BOC Notes on the LEC Networks 1994 SR-TSV-002275
Contents Issue AprIl 1994
4.5.3.1 Equal Access Feature Group 4-31
4.5.3.2 Other Access Feature Groups and 4-37 4.5.3.3 Feature Group A... 4-37 4.5.3.4 Feature Group 4-38
4.5.3.5 Feature Group 4-38
4.5.3.6 operator Services 439
4.5.4 Combined Configurations 4-40
4.6 Reliability of Equipment and Systems 443
4.6.1 Local Exchange Network Hypothetical Reference
Connection .. ._ .4 444
4.6.2 End-to-End Network Availability Objective 4-45
4.6.3 Network Segment Availability Objectives 4-46 4.6.3.1 Distribution Network Segment 4-46 4.6.3.2 Circuit Svitch ...... _ 44.7
4.6.3.3 ISDN Switch.... 447
4.6.3.4 Facility-Entrance Network Segment 4-49
4.6.3.5 Interoffice Network Segment 4-49
4.6.4 CCS Network Reliability and Unavailability Downtime
Objectives .... 4-51 4.7 Network Service Evaluation 454
References ...... 457
Bibliography ...... _ ...... 459
II the LEC Networks SR-TSV-002275 BOC Notes on 1994 Contents Issue AprIl 1994
List of Figures
4-7 Figure 4-1 Hypothetical Local Network within single LATA
4-12 Figure 4-2 Existing Operator Services Systems OSSs
4-20 Figure 4-3 Alternate Routing Arrangement
4-20 Figure 4-4 Relationships Involved in Alternate Routing Arrangement
Figure 4-5 Example of Nonhierarchical Routing Using the DR-T Routing 4-23 Scheme ......
4-27 Figure 4-6 Single Tandem with Alternate Routing
Alternate Figure 4-7 Combined Sector-Tandem Configuration with Multistage 4-29 R.outi.ng S. 430 Figure 4S FhreeLevel Intra1.ATA Network.
A-B Traffic 4-31 Figure 4-9 Dynamic Routing Sequence for .....
Figure 4-10 Basic Interexchange Carrier LATA-Access Routing Cotions 433
Fie 41 Service Prefix Routing
4-35 Figure 4-12 Sectored Routing
A1tPrn2tf Rnutin 4-35 Figure 4-13 _._-__-- 436 Fie414 Terminating Routing 436 Fie415 utofLATA Routing ...... 441 Fie4-16 Single Tandem/Access Tandem
4-41 Figure 4-17 Combined Sector Tandem/Access Tandem.....
Paths 4-43 Figure 4-18 Restricting DRT to Two-link
Reference Figure 4-19 Local Exchange Network Hypothetical Connection 44.5
4-46 Figure 4-20 End-to-End Network Availability Objective
4-48 Figure 4-21 Distribution Network Segment Unavailability Objective
Figure 4-22 Switch Network Segment Unavailability Objective Through 4-48 Path ......
..... 4-50 Figure 4-23 Facility-Entrance Network Segment Availability
4-50 Figure 4-24 Interoffice Network Segment Unavailability Objective.
Downtime for CCS Basic Mesh Figure 4-25 ANSI T1.1l1.6 Objectives 4-52 Network Segments N11P only
III BOC Notes on the LEC Networks 1994 SR-TSV.002275
Contents Issue AprIl 1994
Figure 4-26 Example Case One Trunk Group with Its Terminating CCSSOs 4.53
Iv LEC Networks SR-TSV-002275 BOC Notes on the 1994 Contents Issue AprIl 1994
List of Tables
4-24 Table 4-1 Comparison of Typical Blocking Probabilities SOC Notes on the LEC Networks 1994 SR-TSVOO2275
Contents Issue AprIl 1994
vi the LEC Networke 1994 SR-TSV-002275 BOC Notes on Network and Issue April 1994 Design Configuration
Network Design and Configuration
4.1 Introduction
for and The equipment arrangements and features described herein originating based on terminating calls in Local Access and Transport Area LATA are equipment that exists in some or all intraLATA networks All arrangements described in this
section are intended to operate within these LATA boundaries
4.1.1 TermInal Equipment
the Although terminal equipment is not part of intraLATA networks general show the to and use of the descriptions included here are provided to relationships
associated demarcation points Terminal equipment consists of apparatus provided on receive communications the customer premises that permits user to originate and/or and over the telecommunications network This equipment generally provides incoming
but is not limited to these outgoing signaling and 2-way communications solely functions
in Customer premises terminal equipment must comply with the requirements specified Part 68 of the Federal Communications Commission FCC Rules and Regulations as
the network Terminal with the FCC prerequisite for connecting to equipment registered
in accordance with the requirements in Part 68 can be connected directly to the telecommunications network for those services covered by the FCC Rules and
Regulations
Detailed information describing the electrical interfaces between switching equipment be in LATA and customer premises terminal equipment can found FR-NWT-000064 Section of this Switching Systems Generic Requirements LSSGR1 and in publication
General information is contained in this section
An individual central office line serves only one customer Several terminal equipment
items can be bridged across the line but they are for use by single customer
Since the multiparty line is central office line that serves more than one customer the line at line has one set of equipment at the central office only one customer can use
time Each customer can be selectively signaled using superimposed ringing systems
from either side of the line and by Selectivity is obtained by ringing to ground telephone
using polarized ringers
used Local Exchange Carriers LECs to Multifrequency ringing systems are commonly by independent subscribers These can be connected across the two sides provide selective ringing for party-line ringers the number of does not of the line rather than from one side of the line to ground as long as parties
exceed the available frequencies
4-1 BOC Note on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Network Design and Configuration April
Terminal equipment arranged for outgoing signaling generates supervisory off- or on- Dual-Tone This hook signals and either dial pulses or Multifrequency DTMF pulses arrangement enables the central office or Private Branch Exchange PBX equipment to Carrier other initially establish the routing of the call through Local Exchange LEC or switched networks to its destination
Rotary dials or an electronic equivalent are used to generate dial pulses alternate opens and closures of dc loop that are transmitted on central office or PBX line DTMF keyset is used to generate tones needed to operate central office or PBX equipment The keyset is arranged to generate pair of specific frequencies for each dialed digit
Terminal equipment can be divided into various categories Following is general description of three basic categories
Terminals such as telephone sets data modems facsimile machines and ancillary
devices for example answering sets and automatic dialers
Key Telephone Systems KTSs
PBXs
telephone set or its equivalent is used to communicate by voice over the telecom munications network telephone set is terminal instrument that permits 2-way real time voice communications over the network The set converts voice and voiceband acoustic signals into electrical signals suitable for transmission over the network and conversely converts received electrical signals into acoustic signals telephone set call the network and the usually generates the control signals required to initiate on consists of alerting signal in response to an incoming call telephone set generally transmitter receiver induction coil hybrid switch-hook dial and ringer or electronic sounder Direct current and ringing current are usually supplied from the central office or from the PBX when telephone set is connected to PBX
KTS is an arrangement of multiline telephone-station apparatus and associated or hold calls over equipment that usually allows user to selectively answer originate held buttons specific central office or PBX line Lines are selected or by operating or keys that are mounted either external or internal to the station apparatus Visual indicators usually display line status such as line select busy idle hold and ringing
is Audible alerting generated internally or externally to the station apparatus normally and provided Other features such as intercom capability toll restriction exclusion conferencing are also sometimes provided
within of PBX is an assembly of equipment that allows individuals community users the network to communicate with each other It also provides access to and from by means of trunks between the PBX and the serving central office Connections with the calls PBX are made by the PBX equipment in response to user dialing action Outgoing to central office can also be made by dialing through the PBX switching equipment or
the attendant An access code is usually dialed sometimes by placing them through PBX and the PBX station is terminated to trunk in central office thereby gaining access to the network
4-2 the LEC Networks 1994 SR-TSV-002275 BOC Notes on Network Design and Configuration Issue April 1994
in After the second dial tone address information of the called party is dialed resulting for network connection to the called station An attendant position can be provided
attendant also incoming answering incoming calls and for user assistance The completes
calls to PBX stations except when the PBX provides Direct Inward Dialing DID service With PBX DID service central office call can be completed to the PBX station done since the dial PBX interprets without operator assistance This can be equipment forwarded from the central office and routes the call directly to the digits equipment
station
that be the to Hybrid PBXs/KTSs are systems can arranged through common equipment In is an assembly of perform automatic PBX andKTS functions particularaPBXIKTS within of users to or answer equipment that allows an individual community originate other within the community In calls to or from the public network or users PBX line or hold calls over addition PBXIKTS allows user to selectively answer originate found office line detailed of the interface can be specific central description signaling
in Section of this document
4.1.2 Network Configurations
network of trunks the Switching systems in LATA are interconnected by providing of services The interconnections necessary capabilities for handling variety customer interLATA services trunks provide for both intraLATA and interLATA services For connect most LEC networks to the networks of the Interexchange Carners ICs of and interconnecting trunks is referred to as particular arrangement switching systems on network configuration number of different configurations are possible depending
the number and type of switching systems employed
is The number and placement of switching systems in particular configuration largely and Economic studies dependent on the economic trade-off between trnnking switching most handled show that large volumes of traffic between two points are economically of traffic between two when served over direct trunks Conversely when the volume the demand at intermediate is it is more economical to aggregate points small ordinarily several if the switching systems End-to-end connections can involve switching systems distance originating and terminating points are significant apart
for the and efficient handling of The basic routing arrangements required systematic these nearly always message traffic are defined in network plan Currently plans hierarchical network and automatic alternate routing to provide specify configuration network rapid connections while making efficient use of the deployed equipment
and distribution of traffic for all points configuration must provide for the collection condition on With automatic alternate routing call that encounters an all trunks busy and offered in to one or the first route tested is automatically route-advanced sequence final route more alternate routes for completion until it reaches
considerations to This section describes the network configurations and design applicable
in the provided at the end intraLATA networks The symbols used are defined Glossary
of this document
4-3 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Network Design and Configuration
4.1.3 Switching Equipment
used at Stored Program Control SPC is the most common type of switching equipment end offices and tandem offices These systems use either analog or digital switching
However there are locations that continue to be served by electromechanical Step-by used have the Step and crossbar systems The switching system must capability to send receive and be actuated by the signals discussed in Section
Each callable customer terminal in World Zone is assigned unique 10-digit
of calls address Routing between terminals is based upon this address Proper routing The details of these considerations are found in may require dialing additional digits Section of this document
Signaling between switching systems may use either inband or out-of-band signaling and dial An of out-of- Examples of inband signaling are multifrequency pulse example With and dial band signaling is Common Channel Signaling CCS multifrequency
call is pulse signaling the number of digits actually passed at each stage of the usually end the minimum required to advance the call toward its destination For incoming calls offices office switching systems are arranged to receive minimumof digits End
serving more than one central office code need to receive or more address digits on
incoming calls
24-bit label is used to When Signaling System SS7 CCS is used unique SS7 routing contains 8-bit Destination route the signaling information associated with the call It an Point Code Point Code DPC that identifies the terminating office an 8-bit Originating and OPC that identifies the message originating point the originating office load the Signaling Link Selection SLS field that is used to perform sharing on signaling such the bearer links used to route the message Other information about the call as carrier identification of unlisted capability connection type identification calling
number etc is also sent with the routing label
Most SPC offices can accept and process Carrier Access Codes CACs including End Offices 1OXXX Offices with this capability are referred to as Equal-Access In the 1994/1995 time frame EAEOs and support Feature Group FGD calling FGD CAC format will be 1O1XXXX that is the CAC will be expanded from to the CACs digits Most SPC offices should accept and process new
code for Some end offices are not equipped to accept carrier 1OXXX/1O1XXXX access end offices handle 950-XXXX routing for example SXS offices However these can numbers for Feature Group FGB access and Feature Group FGA access
of Connections established through the network from an originating customers point controlled termination to terminating customers point of termination are generally by Control hook switch status and the originating or calling terminal signals including
dialed to the end office the Integrated Services Digital digits passed originating by Network D-channel or by loop closure and either DTMF or dial pulse signaling the network and will initiate the call This in turn will connect the customer to provide
transmission path between the originating and terminating points The network
various will the call-progress specifically the switching systems provide necessary
4-4 Notes on the LEC Networks 1994 SR-TSV-002275 BOC Network Design and Configuration Issue AprIl 1994
the terminal indicating call progress and an alerting signals to originating equipment that call is waiting signal to the terminating terminal equipment indicating
4.1.3.1 End Office Switching Systems
Telecommunications End office switching systems provide access to the Message Service MTS network telephone user can originate or receive communications to or of the network is to from the network via an end office The basic function provide and communication paths between originating-customer terminal equipment and customers terminating-customer terminal equipment If both originating terminating the communications is the one are served by the same switching system path through in the If the customers are served different switching systems switching system only by intraLATA network If the same LATA the communications path is established via the in different customers are served by Bell Operating Company BOC switching systems the interLATA network via an IC LATAs the path is established through
the of the end office to selectively The traffic network design is based on capabilities called number If the end office is of alternate route traffic according to the capable
traffic distant office can routing generally the case for common-control systems to
all trunks in that are the office can first be routed on one trunk group When group busy direct control alternate route the overflow to another office For noncommon-control or routed trunk systems all the traffic for destination must be over an only-route group their The introduction of SPC capabilities in end office switching systems expands ability
traffic the ultimate network configuration of trunks and to selectively route Thus of the mix of end offices switching systems is dependent on the capabilities
both the route chosen and the of call Distinctly The signaling used depends on type interLATA direct interLATA via different signaling patterns are used for intraLATA accommodate tandem international and operator-assisted calls The network can various of tandem-switched mixture of CCS and multifrequency signaling on the legs
call
4.1.3.2 Host/Remote Switching Unit
of customers SPC switching technology also offers the potential to serve group
is connected to remotely using Remote Switching Unit RSU which controlling and facilities Figure 4-1 host SPC switching system by data link interconnecting extension of the host SPC switching The remote terminal operates primarily as an the remote terminal via the data link from the host At system Commands are issued to these commands and the the remote terminal microprocessor interprets performs
some LECs InterLATA calls may be handled differently by independent
4-s BOC Notes on the L.EC NetworksI 994 SR-TSV-002275 Issue 1994 Network Design and Configuration April
requested functions In addition the microprocessor scans the network and line and these via the appearances in the remote terminal for changes of state reports changes data link the host data link to the host switching system Figure 4-1 The connecting trunk the two units this trunk and remote unit is part of the group connecting Ordinarily
is calls from RSU some group the only one allowed for switched an office however trunk from the remote unit to cuirent host/remote designs have the capability to directly have the to other offices without routing through the host Also some RSUs capability
the data link fail between the allow calling among customers served by the RSU should RSU and the host switch This can be an advantage where the RSU serves an isolated community single.host electronic switching system can control multiple RSUs For some RSUs there may exist host office without lines for example host office equipped with trunks only and no lines
The RSU is smaller and more cost-effective system than traditional stand-alone
switching entities Figure 4-1 One of the attributes of the host/remote distributed
than is system is the ability to start new wire centers at smaller size economically feasible for larger stand-alone systems while still providing the customers in the serving area with all the features of the SPC host system Remote switching has number of applications including Community Dial Office CDO replacement or capping new small wire-center formation and extension of new features or services to electromechanical wire centers
4.1.3.3 Tandem Switching Systems
used interconnect offices direct trunk Tandem switching systems are to end when groups alternate are not economically justified or when the network configuration indicates
the to the routing is economically justified Tandem offices provide ability configure functions network economically act as buffers between different systems and centralize LEC tandem such as billing which may not be available in all end offices switching
systems perform some or all of the following functions
Interconnect end offices
Connect to other tandems
Serve as Centralized Automatic Message Accounting CAMA points for end offices
Provide access to ICs
Provide access to operator positions
In other words tandem switching systems perform trunk-to-trunk switching customer two basic network lines axe not ordinarily connected to tandems and generally provide
functions traffic concentration and centralization of services As traffic concentrators
for tandems allow the traffic of groups of end offices to be economically gathered end offices distant with tandems call recording delivery between the or to points Also be centralized LATA access operator services and signaling conversion functions can and made economically available to groups of end offices Proper deployment of
44 1994 SRTSV-002275 BOC Notes on the LEC Networks Network Design and Configuration Issue AprIl 1994
Unes on Integrated Range Extension
AnalogFacility Remote Switch
Pair-Gain Remote Terminal Digital
Carrier I- End Office
not shown Note All possible configurations are
Local Network Figure 4-1 Hypothetical within single LATA
4-7 BOC Notes on the LEC Networks 1994 SR-TSV-002275 1994 Network Design and Configuration Issue Apr11
tandems is based on the blending of the functional needs and the economics of traffic concentration according to the technical capabilities of the tandems being deployed
Tandem switching systems can be 2- or 4-wire analog or digital depending upon the transmission plan for the networks to which the tandem switches have access and the distance between offices Both 2- and 4-wire trunk facilities can be terminated on analog but tandem switches Digital switches are inherently 4-wire switching systems may contain 2-wire analog interfaces
4.1.3.4 Dynamic RoUthgSwitching Systems
Dynamic Routing Switching Systems commonly called via nodes are used to interconnect end offices when direct trunk group is unavailable Via nodes provide the the total network trunk ability to configure the network economically by reducing requirements via node interconnects end offices in the same way as tandem switching system but is also used as an end office thus utilizing idle trunks in the network Proper use of via node is determined by collection of current network data at centralized controller Dynamic Routing Switching Systems must be SPC
4.1.3.5 Combined Systems
Recognizing that dedicated tandems serving rural or other low-volume areas may not of end necessarily be cost effective tandem capabilities have been added to variety hardware and software office technologies The combined systems share portions of the
as an efficient compromise to meet both customer service needs and network requirements
4.1.3.6 Digit Utilization and Translation
Routing within an intraLATA network is done sequentially by each switching system as
call progresses To do this each office must be able to examine the destination-code digits received to select an outgoing route and determine the proper signaling to pass to the next switching system
numbers the of destination-code The dialing plan for geographic employs principle routing Each customer terminal in World Zone is assigned unique 10-digit number and station that consists of 3-digit area code 3-digit central office code 4-digit number
of call When Several methods are commonly used for treating the address digits an intraLATA Foreign Numbering Plan Area FNPA can be reached by more than one number of each route the first digits area code and central office code of the 10-digit to determine the call to an FNPA are examined by the originating switching system
In all of the can be deleted other preferred outgoing route addition or part digits the can be converted to other on the digits can be prefixed or digits digits depending
4-8 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Network and Issue AprIl 1994 Design Configuration
address information must be requirements of the switching system to which the forwarded This process is called 6-digit translation
Digit deletion is used for various purposes including the following
To drop an area code when pulsing into that area
be substituted for To drop an area code or central office code when other digits are to
them this is called code conversion
of central office code when the code are all that To drop part or all remaining digits
are necessary to route the call to that office delete or digits
deleted is of the number of used for The number of digits that can be independent digits
deletion with the first received selecting the outgoing route Digit always begins digit
the of One to six digits can be prefixed to the received digits depending upon type Plan Area code to switch An example is the prefixing of the Home Numbering HNPA the central office code and station number received
substitution of Code conversion is capability in some systems which permits the digits in for some or all of the digits received This feature provides flexibility meeting numbering plan requirements by furnishing routing digits for certain switching systems in the network for example to establish call through an SXS system that requires
The last routing digits different from those provided by the 7-digit address preceding tandem office can delete some of the digits and furnish instead digits that fit the
Another is the of the dialed switching pattern of the SXS system example converting number for digits 911 to 7- or 10-digit telephone routing
4.1.3.7 Trunk Circuits
Trunks between switching systems are most commonly carried on channels of digital carrier systems Digital Signal level and higher-order multiplexes However some individual analog circuits on copper cable pairs and some Frequency Division
Multiplex FDM carrier systems are employed
each trunk Analog SPC and electromechanical switching systems must treat as an full DS1s individual analog circuit Digital SPC systems usually treat or higher-order of the channel without conversion to multiplexes and switch the digital contents analog
trunk and the The following paragraphs describe the relationship between types
connection types that are supported
and Voiceband or 3-kHz connections may use either analog or digital trunk channels 56 must use either multifrequency or CCS signaling Data connections at kbps digital CCS the use of trunk channels and may use either multifrequency or signaling However limit the of use of that channel multifrequency signaling may flexibility
to kHz or 64 Clear-Channel Digital trunk channels designed carry kbps require such as CCS for interoffice Capability CCC and thus require out-of-band signaling
4-9 SOC Notes on the LEC Networks 1994 SR-TSV-002275 issue 1994 Network Design and Configuration April
in signaling Detailed requirements for trunk signaling are contained FR-NWT-000064 LATA Switching Systems Generic Requirements LSSGR
4.1.3.8 Call Control
Recorded announcements and various tones are used to advise the calling customer of
will receive either recorded call progress On most calls the calling party
announcement or call progress tone Control of the connection is achieved as follows
immediate control of On customer-dialed calls the connection is usually under The of the called the calling customer and under delayed control timed disconnect
for various is customer The range of disconnect timing intervals switching systems shown in Table 6-8 in Section of this document
On operator-dialed calls the connection between the operator and the calling actions have customer is under joint control except where the operator performs to
sole control of the call
4.1.4 Interexchange Carrier Points of Presence
Point of Presence POP is location within LATA that has been designated by an IC
for the connection of its facilities with those of LEC Typically POP will be at
and it be located building that houses an ICs switching system or facility node must within the LATA that the IC serves An IC may have more than one POP within
LATA and POP may be for public and private switched and nonswitched services One location may serve as POP for several service types
Termination The IC is required to designate at each POP physical Point of P01 the The consistent with the technical and operational characteristics specified by LEC functions and the POT provides clear demarcation between the LECs exchange-access IC interLATA functions and enables the LEC to meet its tariff obligations This POT
item of at which the generally will be distributing frame or other equipment LEC verification access lines terminate and where cross-connection testing and service can
occur The IC can also have multiplexed Time-Division Multiplexing
Frequency Division Multiplex etc POT interface which requires special
testing procedure
4.2 Operator Services Systems
telecommunications Although the vast majority of calls that are placed through the situations and/or network are established directly by the customer there are many functions services that services that require an operator There are also certain or automated Both access to previously required an operator that are now fully operators the via the Services and some automated functionality are provided to customer Operator System OSS
4-10 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Network Design and Issue AprIl 1994 Configuration
be into broad categories Assistance Services provided via the OSS may grouped two and Information
assist customers in the completion Assistance operators and automated functionality of services also be trained of calls and in special or alternate billing Operators may of services or available to to provide assistance on the proper use optional capabilities
the customer
customer information Information or Directory Assistance operators provide listing via database accessible the telephone numbers address information etc by accessible the customer Intercept is also operator or in some cases directly by included in this category
from which customers access The OSS serves as call-processing switching system may
in order to calls or gain access to operators or automated functionality complete information Some additional functions accomplished by the OSS include automatic call
and information retrieval Additional distribution recording of billing details Services information may be found in Beilcores FR-NWT-000271 Operator Systems
Generic Requirements OSSGR.2
4.2.1 Existing Architecture
in 4-2 This generic view of the existing OSS architecture is shown Figure figure end offices tandem shows that an OSS may have access to operator positions databases from which offices and other OSSs The OSS may also serve as platform new be to services or functions technology such as speech recogthtion can applied existing service based on service codes dialing The OSS is capable of identifying the requested information The is of patterns trunk groups and/or signaling system capable automated based on these identified distributing calls to attendant positions or peripherals
service needs
4.2.2 Future Architecture
of the architecture The future OSS architecture will be based on the evolution existing of the OSS to allow new services to provide Emphasis is being placed on the flexibility calls under the control of other network elements operator or automated functionality to the OSS into the Advanced Intelligent and to fully integrate functions provided by OSS is to be that of Automatic Network AIN concept The future role of the expected calls attendants or Call Distributor ACD that is enqueueing and dequeueing requiring of the calls All associated automated functions and recorder of billing details processed would be resources databases attendant positions automated platforms etc provided accessed via the OSSs tall distribution functionality via intelligent nodes or platforms role with descriptions of the AIN This concept of the OSSs future concurs published
4-11 SR-IS V.002275 BOC Notes on the LEC Networks 1994 issue AprIl 1994 Network Design and Configuration
Network
Network
OSS Supporting Databases
Services Figure 4-2 Existing Operator Systems OSSs
4-12 SR.TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Network Design and Configuration
4.2.3 055 Switching Environment
An OSS is tandem switching system with special operator services capabilities Some
OSSs serve only operator services traffic in stand-alone environment in other words tandem functions are not provided Others reside on Access Tandem AI switches that
also serve nonoperator services traffic Additional hardware and software is necessary of services for switching system to be capable providing operator
4.2.4 Position in the Network
The OSS receives calls from end offices from LEC tandems and from other operator
systems both LEC and IC An OSS is capable of completing calls to LEC end offices
and of routing calls to an ICs POP The OSS may also route calls to other OSSs Some terminate the service calls OSS-provided services at system such as some listing OSSs
and automated service call combined end office trunk normally receive operator types on groups The OSS sorts the traffic by call type and distributes each call to the resource needed for call proccssing
4.2.5 Call Handling
After recognizing request for service an OSS will begin initial call processing to determine call type This initial processing may also determine originating station restrictions if applicable to the requested service If the service is intraLATA the OSS will either serve the call or pass it to another system that can provide the requested
service on the LECs behalf If the call or service is interLATA in nature the preferred IC is determined and the call is either served by the LEC OSS on behalf of that carrier
prearranged service contracts must be in place or the call is passed to the IC for handling
4.2.6 OSS Subsystems
To accomplish the provision of operator services the OSS depends on the core switching capabilities of the OSS and numerous subsystems and databases that are accessed at the direction of the core The various components that make up the subsystems and databases are frequently developed and provided by multiple suppliers In order to promote an environment in which this arrangement can function efficiently open non-proprietary interfaces between the components are strongly recommended Many of these non- proprietary interfaces are specified in Beilcore sFR-N Wr-00027 Operator Services
Systems Generic Requirements OSSGR.2
Some examples of subsystems and databases that may be used by an OSS are listed below
Position Subsystem This subsystem provides the means by which the core switch
can attach an attendant to call The position equipment may consist of terminals
4-13 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Network Design and Configuration issue April 1994
simply displaying information provided by the core Recently deployed intelligent
workstations can be equipped with software layer that provides additional displays or attaches additional call processing resources based on the basic core-provided call
details
Databases Databases are used to store information that is needed for call
services customers processing and to provide listing-information-based to An the of call individual database may be accessed directly or indirectly by core as part directed processing by the position subsystem at the direction of an attendant or as
by other OSS subsystems Examples of these databases include the following
Line Information Database LJDB
Listing Services Database LSDB
Intercept database
Operator Reference Database ORDB
Real Time Rating System RTRS
Announcement Subsystem This subsystem provides audio information to system
users on an automated basis Recent applications have implemented speech
recognition and speech processing capabilities for use in interactive functionality
between the customer and fully automated services
for administrators Report Subsystem This subsystem prepares reports system
and/or provides data for downstream processing and report generation
4.2.7 Features
The features provided at the OSS may be divided into several categories those common
to the basic OSS functionality customer access access to customer listing information
service specific call-handling and special billing
4.2.7.1 Basic OSS Features
Features common to the basic OSS include determination of calling called and billed call number This capability enables an operator or the system itself to enter selected details This functionality includes basic validity and format checks
Service Determination and Handling Methods allow an operator to enter or the method the system to determine the specific service and the handling requested by
caller
the determine Initial Call Processing provides the capability for OSS to customer- information dialed digits and to request and interpret post-seizure dialing
IntraLATA/InterLATA Check provides the capability to determine whether request
for call completion is intraLATA or interLATA
4-14 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Network Design and Configuration
IC Code Processing allows the OSS to offer service on behalf of or to direct calls to ICs
Sequence Call Processing allows customer to request further action/services while connected to the OSS
Tenninating Inward Service provides the capability to receive requests from other
OSSs for service on various calls including emergency assistance call completion and other services busy-line verification operator interrupt operator-handled
4.2.7.2 Customer Access Features
Customer access features provide the capability for customer to access an operator in order to obtain information relating to services dialing instructions or general assistance
the traditionally provided by operator
Rate Information allows the operator to provide customer with information about
charges for specific services
call in order obtain the CAMA allows an operator to be bridged onto to calling
billing number from the customer
Credit Recording provides the capability for an operator to enter customer credit calls that encountered number network trouble requests for wrong or
Trouble Reporting provides the capability for an operator to report customer- encountered network difficulties by keying trouble codes and details into the OSS
4.2.7.3 Customer Listing Information Features
obtain information Customer listing information features allow customers to through the via machine listed OSS either from an operator or an announcement Examples are below
Directory Assistance provides the capability for customer to obtain the listed
telephone number for given name and address
Customer Name and Address Service allows customer to obtain the mi1ing address
associated with given telephone number
Area Business Listings allow customer to obtain business listings based on given
geographic area and the business category or trade name
Data associated with these and other listing services are not retained in the OSS but in databases that are accessible by the OSS
4-15 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Network Design and Configuration issue April 1994
4.2.7.4 Service Specific Call Handling Features
The OSS can provide functionality or automation specific to certain services or classes of services Note These services may or may not be optional in their offering or pricing
Message Delivery is feature that allows customer to record message to be
delivered to specified station by the OSS
Busy-Line Venfication is feature that provides the capability for calling customer to
the of line request that an operator verify current status given
Operator Interrupt provides the capability for an operator at customer direction to
intermpt an established connection
Conferencing is feature that allows three or more customers stations to be bridged
together on single call
OSS call handling for specialized attendant groups uses the ACD functionality of the
OSS to distribute incoming calls to specialized attendant groups that provide services unique to the callers service code or other identifying characteristic of the originating call
4.2.7.5 Special Billing Features
Special billing functions enable the OSS to provide alternate billing that is calling card collect and third number billing Common to all of these billing methods is the capability of the OSS to verify the billed number via access to the LIDB in which the billed number resides This validation process is provided via data messages launched and replied to on the existing SS7 network
Calling Card Billing allows customer to place call and have the charges
associated with that call billed to valid calling card
Collect Billing enables the calling customers capability to bill the charges associated
with call to the called customer This billing method requires verbal acceptance
from the called party
Third Number Billing allows customer to bill call to valid telephone number that
is neither the called nor the calling number
Originating Line Number Screening is the OSS feature that queries the LIDB to
determine what billing or service restrictions if any are associated with the calling
station
4.2.8 Telecommunications Relay Service
Telecommunications Relay Service TRS is telephone transmission service that provides the ability for an individual who has hearing or speech disability to engage in communication with hearing individual in manner that is functionally equivalent to
4-16 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Network Design and Configuration
does have or the ability of an individual who not hearing impairment speech impairment TRS includes services that enable 2-way communication between an individual who uses Text Telephone TI or other nonvoice terminal and an individual who does not use such device
actions have mandated that be made available Several regulatory and legislative TRS
actions is the Americans with Disabilities Act which Most significant of these ADA
prescribes that
Each common carrier shall provide TRS individually through designees through
competitively selected vendor or in concert with other carriers
In addition the ADA directed the FCC to prescribe regulations establishing functional for In the Docket requirements guidelines and operations procedures TRS FCC No
90-571 the Commission provided such regulations Key among them is technical
ICs it is stated that standard that prescribes equal or equivalent access to Specifically
TRS users shall have access to their chosen interexchange carrier through TRS and
to all other operator services to the same extent that such access is provided to voice users
In each state TRS is provided after selection/certification bidding process by single
carrier either an IC LEC or other usually nonprofit organization
has been that the The regulation prescribing equal access for TRS interpreted to require call TRS provider offer the TRS user the ability to designate the carrier to transport the
by using Feature Group FGD signaling to the LEC access tandem Accordingly the TRS provider must establish the technical capability and the administrative procedures to
route the call to the designated transport carrier Similarly the transport carrier must be
able to recognize the TRS call complete the call to its destination and obtain sufficient
call detail information to accurately rate and bill the call With such an arrangement the
established connection will link the calling party to the called party through the TRS
platform and the facilities of the transport carrier
the In order to provide the technical capability as specified in the FCC Docket and meet
requirements of the ADA workshop was established under the auspices of the Industry
Carriers Compatibility Forum ICCF to develop and propose the necessary technical
arrangements to accommodate TRS The final output of the TRS Workshop entitled IRS of Technical Needs ICCF 93-0729-008 presents the current industiy understanding
network technical issues associated with the implementation of TRS.3 The document
which should be considered the product of industry consensus also proposes the technical arrangements and the ultimate network solution to the stated issues
4.3 Network Design Considerations
The successful completion of traffic dialed by customers and operators depends upon
trunking network in which no-circuit conditions are rarely encountered under expected
conditions Alternate or dynamic routing and selection of appropriate blocking
4-17 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Network Design and Configuration April
with reasonable trunk This section discusses probabilities make this possible efficiency
network design considerations for intraLATA services that may not apply to LATA and access services See SR-TAP-000191 Trunk Traffic Engineering Concepts
Applications for detailed discussion.4
traffic first- The principle of alternate routing is applied to telephone by providing for item of and alternate route choice high-usage route given traffic second-choice
when calls fail to find an idle trunk on the first-choice route Additional alternate routes
can be provided subject to routing restrictions
traffic The principle of dynamic routing is applied to telephone by updating routing the basis of trunk measurements patterns on real-time or short-time interval on group collected by network central controller
4.3.1 Fundamentals of Hierarchical Routing
minimize Alternate routing is advantageous because it provides the opportunity to the
load is allocated cost per unit of carried traffic With alternate routing the to high-usage
and fmal routes in the most economical mnnner Alternate routing also permits the
meshing of traffic streams that have differing busy hours or seasons
Figure 4-3 illustrates 1-way high-usage trunk group from end office to end office
with an alternate final route via tandem In general the direct or high-usage route is
shorter and less expensive than the alternate-route path However because each leg of
the alternate route is used by other calls number of traffic items can be combined for
improved efficiency on that route The basic engineering problem then is to minimize
the cost of carrying the offered load that is to determine how much of the offered load
should be carried on the direct route and how much should be overflowed to the alternate
route
function of the Figure 4-4 shows the relationships involved The graph shows as
number of trunks in the high-usage trunk group the cost of the direct route the cost of
the alternate route and total cost for serving the given offered load The high-usage
trunk group cost of course increases in direct proportion to the number of high-usage trunks If there are no high-usage trunks all of the offered traffic must be carried on the
alternate route so the incremental alternate-route cost is high As trunks are added to the high-usage trunk group less offered traffic is overflowed to the alternate route so that the incremental alternate-route cost decreases This cost decreases very rapidly as the first
trunks are added to the high-usage trunk group This is due to the efficiency of each of
these trunks which relieves substantial amount of load from the alternate route As
more high-usage trunks are added each successive high-usage trunk carries less traffic
This principle can be illustrated with an SXS switching system offering call to group of ten 1-way outgoing trunks Tested in order think No will be selected first reselected when idle and thus be kept busy mostof thetime TrunkNo 2willbeslightlylessbusyandtrunkNo 3will beusedless than
No This pattern will continue to the tenth think which is called into use only when all prior trunks are busy
4-18 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Network Design and Configuration
while each alternate-route trunk continues amount of traffic to carry significant
Eventually it becomes undesirable to add any more high-usage trunks The point at
which this threshold occurs is where the total cost the sum of the two curves is
minimized This point is designated as in Figure 4-4
method commonly used to determine is called Economic Hundred Call Seconds
ECCS engineering This method determines the maximum number of high-usage
trunks for which the cost per hundred call seconds CCS carried on the last trunk of the high-usage tnmk group is less than or equal to the cost per CCS on an additional
alternate route trunk
This relationship can be expressed by the following equation and is the basis of ECCS
engineering
CALT 28 CHU ECCS
Where CALT Cost of path on the alternate route
CHU Cost of trunk on the high-usage route
28 Capacity in CCS added to the alternate route by the addition of an incremental trunk path
The equation is solved for the ECCS the load to be carried by the last or least- efficient trunk in the high-usage trunk group Given the ECCS and the offered load standard trunking tables can be entered to determine the number of trunks required and the estimated amount of overflow This is the largest number of trunks for which the
load carried on the last trunk is not less than the ECCS
Since the equation is solved for the ECCS the other elements of the equation must be known The left portion of the equation CALTICHIJ is the cost ratio or the relationship of the cost of path on the alternate route to the cost of trunk on the direct route Cost ratios used for alternate-route engineering are always greater than unity
The 28 shown in the equation is the incremental capacity of the alternate route the capacity that would be added to the alternate route by the addition of one path This value is usually assumed to be constant of 28 CCS thereby permitting calculation of the ECCS as function of single variable the cost ratio
Thus it can be seen that with low cost ratios the ECCS will be high and fewer high-usage trunks will be provided Conversely low ECCS would result from high cost ratio and
greater number of high-usage trunks will be provided Simply the more expensive the alternate route relative to the high-usage trunk group the less traffic that will be overflowed to it
4-19 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Network Design end Configuration iaaue April 1994
Tandem
Alternate Route
End Office End Office
High-Usage
Figure 4-3 Alternate Routing Arrangement
Total
High-Usage
Cost
Number Of High-Usage Thinks
Figure 4-4 Relationships Involved in Alternate Routing Arrangement
4-20 SR.TSV-002275 BOC Notes on the I.EC Networks 1994
Issue AprIl 1994 Network Design and Configuration
The total cost curve is rather flat near the minimum As result errors in ECCS that might result from minor cost ratio or incremental CCS errors will not have significant impact on network cost
The number of high-usage trunks to be provided in group depends not only on the
ECCS and offered load but on the variability of the offered load as well This variability can be either within the hour usually peakedness or day to day Such variability can be
it be the result of traffic patterns as in the case of day-to-day variations or can system- induced as is usually the case with peakedness In either event the effect of such variability is reduction of the capacity of group of trunks Where such variability is present equivalent random-engineering techniques are required for the high-usage groups and Neal-Wilkinson capacity tables are used to size grade-of-service engineered fmal trunk groups
Traffic volumes reach peaks during certain hours Trunks are usually provided to care for average-time consistent busy-hour loads in the busy season of the year Where only one outlet trunk group is available trunks must be provided for the group busy-hour load If two routes direct and an alternate route are available however the busy hours on each of the two routes will frequently be different Where this is the case trunks only need to be provided on the direct route to care for that portion of busy-hour offered load that cannot be carned on idle trunks in the alternate route The alternate route may be sized for different busy hour and thus is not fully loaded in the busy hour of the direct route
Often there are two or more potential first-choice alternate routes for high-usage group
The selection of alternate routes can be based on routing discipline if overall cost differences are not significant or the choice can be based on the economics of each individual case that is selection of the least expensive alternate route In general the overall network economics are not highly sensitive to variation in alternate-route costs
New high-usage trunk groups are ordinarily established when offered loads are large enough to justify them Using cost-ratio techniques alone trunk groups with as few as one trunk can be economically justified However other factors such as administrative costs traffic measurement variability modular trunk engineering and the cost of certain central office equipment should be considered in establishing minimumtrunk group size The deployment of digital switching systems digital trunk interfaces and digital transmission facilities provides the opportunity for modularization of trunk groups to achieve equipment and administrative cost savings The specific modularity rules are given in SR-TAP-000191 Trunk Traffic Engineering Concepts and Applications.4
4.3.2 ApplicatIon of Alternate Routing
The principle of alternate routing is basic to the design of the network and is used extensively to provide economic and service advantages Switching equipment automatically seeks alternate routes Calls can be offered in succession to series of alternate routes via one or more tandems At each switching system all of the high- usage trunk groups to which call can be offered are kept very busy with portion of the
4-21 BOC Notes on the LEC Networks 1994 SR.TSV.002275
Network Design and Configuration Issue April 1994
traffic overflowing to another route The final trunk groups are fewer in number and
have low blocking so that the engineered level of service is good The overall chance of trunk completing call is improved by the fact that it can be offered to more than one of service between group Switching equipment operates rapidly and the change in speed
the selection of direct and alternate routes is not significant
In an emergency situation of limited impact and extent such as localized equipment of service failure the ability to use an alternate route adds another measure protection to
However if there is heavy surge of traffic over an entire area for example during
major disaster such as hurricane there is little margin to absorb such surges in load and service may not be as immediately available as it would be with an only-route-type network
In addition to the fmal trunk groups that connect end offices to their home tandem high- end offices and tandems when usage trunk groups are provided from end offices to other that should be considered justified by economics and traffic volumes The traffic items
when evaluating traffic volumes for the purpose of proving-in new high-usage groups are
subject to the rules of the network hierarchy
There are in many cases no direct routes for calls to low-volume points Calls between
end offices not directly connected are completed over two or more trunk groups in tandem tandem switch in hierarchical network will always be involved in multilink
two or more trunks connections
be Since every end office is connected to tandem the tandem network can used to
provide an alternate route for each of the high-usage groups Therefore fewer high-usage
trunks are required Furthermore with the ability to alternate route via tandem it
generally becomes economical to accommodate growth by establishing new high-usage
groups of small size
4.3.3 Fundamentals of Dynamic Routing Technique
Dynamic Routing Technique DRT is traffic routing method in which one or more
central controllers determine near real-time routes for switched network based on the
state of network congestion measured as trunk group busy/idle status and switch
congestion The choice of traffic routes in hierarchical network is static preplanned and
fixed over time other than the manual or automated controls performed by Network
Traffic Management NTM in response to localized or general network overload
Using DRT network traffic can be more efficiently distributed over the network trunk
groups and switches than traffic muted on the hierarchical network Based on near real time network traffic congestion DRT selects routes that provide lower blocking than
todays fixed routes can attain Consequently DRT can reduce the level of demand
servicing and react more easily to relieve problems associated with forecast errors Also
traffic if switch fiber link fails than networks using DRT can carry significantly more or networks using hierarchical routing
4-22 SR-TSV-002275 BOC Notes on the LEC Networks 1994 and Issue AprIl 1994 Network Design Configuration
in least DRT differs from current routing operations at two important areas
the frequency of traffic data collection and application of this data to the selection of routes This dynamic routing algorithm commonly called DR-T can use traffic data collected about every minutes to change routes after each data update where is fixed from near zero to about five minutes
in where can Routing using the DR-T scheme is illustrated Figure 4-5 any node originate traffic and also act as via node The choice of routes can change in the next T-minute period
In nonhierarchical muting switches could originate and terminate traffic and also be used for via traffic
the At the beginning of the update interval of length for example minutes ordered routes for first-offered traffic from switches to determined by the DR-T algorithm could be A-B A-C-B
The ordered routes from switches to could be C-D-B C-B
Figure 4-5 Example of Nonhierarchical Routing Using the DR-I Routing Scheme
4-23 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Network Design and Configuration Issue AprIl 1994
4.4 Blocking Probabilities
Trunking service objectives are expressed in terms of the percent of calls blocked on fmal
and only-route groups in the average time consistent busy hour of the busy season With
given load the degree of blocking is function of the amount of trunk idle time handle calls available When the idle time is low there is little capacity available to new
and the blocking rate is high When the idle time is high there is capacity available to
handle new calls and the blocking rate is low For example with random offered load
of 406 CCS the different trunk capacities and idle times required to achieve B.0l and
B.02 blocking according to the Neal-Wilkinson theory are shown in Table 4-1
Table 4-1 Comparison of Typical Blocking Probabilities
Offered Load Peakedness of Trunks Percent Percent
Blocking CCS Offered Load Required Occupancy Idle
B.O1L 406 1.0 20 56 44
B.02L 406 1.0 18 63 37
It should be noted that there is more idle time with B.01 service than with B.02 service
Trunk groups engineered on B.0l basis therefore do not react as severely to overloads as when higher blocking probabilities are used This applies to all levels of offered load
B.01 objective for engineering trunk group does not necessarily mean 1-percent overall or point-to-point blocking If the group is an only-route group B.01 blocking can be expected in the average time consistent busy hour of the busy season At other periods of the year or during other hours of the day probability of blocking is substantially lower If the B.01 objective is used on an alternate-route final group the blocking in the network that it is part of is expected to be considerably lower even in the average time consistent busy hour of the busy season For example if 50 percent of the calls first offered within the of those were to high-usage groups network only percent overflowing to the final group as an alternate group would be subject to trunk blocking In such case the average blocking in the total network would be closer to B.005 than to
B.01 In other words blocking within alternate-route networks is always substantially less than the blocking objective for final groups
Trunks are provided in such quantities that the probability of blocking including switching equipment blocking in the chain of connection constitutes satisfactory overall Grade of Service GOS This requires careful consideration of all factors involved in meeting the objective of balanced service and cost Based on the expected number of links per connection and the relative numbers of trunks in high-usage and final groups the use of B.01 as the quality-of-service objective for final groups produces in theory overall trunking service in the B.0l-to-B.02 range under average conditions
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issue Aplil 1994 Network Design and Configuration
4.5 LATA Network Configurations
LEC intraLATA networks serve both intraLATA and LATA-access traffic
Configurations for intraLATA traffic are discussed first and then LATA-access configurations are discussed in Section 4.5.2
4.5.1 IntraLATA Configurations
LATAs vary in shape and size as well as in population density and distribution Within
given LATA configurations for the distribution of intraLATA traffic can be characterized as metropolitan high-volume short-distance and nonmetropolitan low volume long-distance LATAs can be served by variety of configurations
Metropolitan local-tandem networks because of the high degree of direct trnnking have in the past served less as point of concentration and more as means to convert incompatible electromechanical end office signaling schemes The evolution to SPC end offices reduces the reliance on local tandems for both signal conversion and traffic concentration and provides smooth transition to DRTs The availability of large digital tandems provides the opportunity to replace several electromechanical tandems with single digital tandem This combination and deployment in metropolitan networks has the following advantages
Growth follows an orderly modernization pattern from electromechanical to electronic tandems
lower total network cost can be achieved that is the number of tandems can be
stabilized by replacing an existing smaller tandem with larger system that better
absorbs network growth or by reducing the number of tandems by employing
dynamic routing scheme
Transmission performance is improved
In some metropolitan networks intraLATA and interLATA traffic remained combined and was carried by the same network components for permitted transitional period following divestiture However the required separation of the networks has now been largely realized and intraLATA and interLATA traffic is combined only at access tandems and on end office-to-access tandem trunk groups as discussed in subsection 4.5.3
In nonmetropolitan areas several electromechanical CDOs may be clustered around larger office serving larger community The interoffice traffic is handled by using the tandem capabilities of the larger and more modern centralized end office As the CDOs
direct be are replaced by SPC systems high-usage trunk groups can economically built between these systems to reduce the tandem load The conversion to host/remote systems also reduces tandem requirements
4-25 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Network Design and Configuration Issue AprIl 1994
4.5.1.1 Routing
The routing rules for the intraLATA network are based on the alternate route network design principles discussed in Section 4.3 The provision of high-usage trunk groups is dependent upon the offered loads and design parameters With SPC switching systems the practicality of establishing 2-way trunk groups increases the opportunity for more directional high-usage groups than would be possible on 1-way basis Also for given loads single 2-way group is more efficient than pair of 1-way groups sized for the directional loads Another advantage of 2-way groups is that they can automatically adjust to changes in the direction of the offered load
With some older end office switching equipment some traffic cannot be routed directly from end office-to-end office on high-usage or only-route trunk groups even though there is sufficient load to support such groups and the end offices are capable of direct routing This traffic and traffic from less capable offices must be tandem-routed for the following reasons
CAMA Recording Any traffic requiring detail billing must be routed to tandem
for CAMA recording for end offices that have no capability for Local Automatic Message Accounting LAMA recording
Pulse Conversion Some end offices do not have trunk circuit pulsing that is
compatible with all other offices and must use tandem for pulse conversion
Six-Digit Translation Some end offices do not have 6-digit translation capability or capacity for certain number services for example 800 or 900 Service and must
use tandem for translation or concentration
4.5.1.2 Blocking
The design of the intraLATA network is generally based on blocking probability criteria of B.01
4.5.1.3 Configurations
When considering the design of an intraLATA network different configurations may be appropriate depending on the traffic demand and end office capabilities within the
LATA Three configurations will be discussed single-tandem two-level networks multitandem two-level networks and three-level networks
In an environment of common control and SPC end offices the single-tandem iwo-level network with alternate routing is the logical choice for many LATAs The single-tandem network is two-level configuration in which overflow from all high-usage trunk groups is routed via the single tandem First-routed traffic is also routed via the tandem where high-usage trunk groups between end offices are not justified or where certain tandem functions are required
4-26 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Network and Issue AprIl 1994 Design Configuration
The tandem the Figure 4-6 is an example of single-tandem configuration provides
and and the first route for overflow route for high-usage groups A-B A-C C-B C-A B-A
and B-C traffic In this example all trunk groups are shown as 1-way although 2-way for the groups should be established as permitted by economics and equipment types final-trunk terminated previously stated reasons It should be noted that only groups are at the tandem The high-usage trunk groups connect end offices First-routed and
overflow traffic are merged on the tandem trunk groups to effect trunk economies
The single-tandem alternate-routing configuration offers the advantage of greater when to nonaltemate-route flexibility and lower cost compared configurations Two
for call offered first to possible routes are available any high-usage group
Unanticipated loads between end offices can often take advantage of temporarily idle tandem route capacity on the
the overflow route for traffic first-routed on In any network where the tandem provides high-usage trunk groups the tandem is subject to congestion from overload Small increases in the load offered to the high-usage trunk groups can result in large increases
in the load overflowed from those groups and then offered to the tandem The sensitivity
of the tandem to network overloads is function of the size of the trunk groups incoming
to the tandem Larger trunk groups because of their higher occupancy saturate sooner calls at the Network and protect the tandem by blocking originating switching system will controls usually consisting of alternate-route cancellation at subtending offices function overloads ordinarily ensure that the tandem can continue to effectively during
Tandem
High-Usage Trunk Group
FinaJ or Only-Route Trunk Group
Aftemate Route
FIgure 4-6 Single Tandem with Alternate Routing
4-27 BOC Notes on the L.EC Networks 1994 SR-TSV.002275
Network Design and Configuration issue AprIl 1994
When growth causes the tandem requirements in metropolitan area or LATA to exceed
the capacity of single tandem an additional tandem or tandems must be added This is
done by sectoring the area with each tandem serving sector resulting in multitandem
two-level network
The combined sector tandem configuration is two-level Multialternate Route MAR
arrangement that provides maximum of four routes between any two end offices
depending on the number of high-usage trunk groups that are justified
Figure 4-7 depicts three-sector arrangement with full complement of trunk groups The first-choice route between and end offices is the high-usage group A-B the
second-choice route from to is via the distant tandem A-T2-B the third-choice
route is via the home-sector tandem A-Ti-B and the last-choice route is via the intertandem final trunk group A-T1-T2-B
The three-sector configuration depicted in Figure 4-7 can be expanded to four or more
sectors by interconnecting all sector tandems with final trunk groups using these same
routing patterns All features of the combined sector-tandem configuration are retained
with this arrangement
High-usage trunk groups in the combined sector-tandem configuration can be either 1- or
2-way The final route to and from an end office is via its own sector tandem High-
usage trunk groups are established in accordance with the criteria for load accumulation and trunk-group sizing
The combined sector-tandem configuration so named because both incoming and
outgoing traffic for sector are combined on the same tandem is preferable over
directional tandem configurations It provides the greatest flexibility because of its
extensive alternate-routing capability and its ability to adjust to changing traffic patterns and load conditions
Several sectors or individual two-level networks within LATA may be interconnected
intertandem trunks between all of tandems form by establishing pairs to one large two- level network However it may be more economical to designate one or more tandems
as principal tandem thus creating three-level network
Figure 4-8 shows that the second-level or sector tandems would be interconnected by with the high-usage groups overflow routed to the principal tandem Not all possible Where high-usage groups are shown high-usage intertandem groups are not justified
the traffic would be routed to the principal tandem End offices could have high-usage
groups to the principal tandem but only for its sector tandem function In LATAs with multiple-principal tandems sector tanderns could establish high-usage groups to distant principal tandem based on economics sector tandem would home or final-route to only one principal tandem
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.-
/\ I%
-.
... .-
.- .% .-
SECTOR SECTOR SECTOR
Route AC
Rrst A-B A-C Second A-T2-B A-T3-C
Third A-Ti -B A-Ti -C
Fourth A-Ti -T2-B A-Ti -T3-C
Note All Trunk Groups Can Be i-or 2-Way Trunk Groups In This iliustraton Are Shown 2-Way For Simplificalion
High-Usage Trunk Group
Final Trunk Group
Alternate Route
Figure 4-7 Combined Sector-Tandem Configuration with Multistage Alternate
Routing
4-29 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Network Design and Configuration Issue April 1994
Pndp Tandem
Sector Tandems
End Offices
Figure 4-8 Three-Level intraLATA Network
4.5.2 DynamIc Routing Configuration
For every designated period and for every pair of switches and in the Dynamic
Routing network the controller computes the following routing sequence for A-to-B traffic Figure 4-9
Direct path The first choice path in the routing sequence is AB
Alternate path The next path in the routing sequence is nonhierarchical path that is path of the form AVB where is DRT network switch used as the via
node DRT routing sequence may or may not include an alternate AVB path depending on whether the central controller can fmd suitable via node
Tandem path if AB is high-usage trunk group then the last path in the DRT routing sequence will be ATh where is the homing tandem of the switches
and If AB is direct fmal then the DRT routing sequence will not include the tandem path ATh
4-30 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Network Design and Configuration
will either links When the Thus path in dynamic routing sequence have one or two
controller computes nonhierarchical alternate path AVB the dynamic routing sequence will be AB-AVB-ATB if AR is high-usage trunk group If AB is direct final the routing sequence will be AB-AVB
Tandem Trunks Are Still The Finals
The controller will not recommend the intermediate path AVB if no suitable via node
is available
Figure 4-9 Dynamic Routing Sequence for A-B Traffic
4.5.3 LATA-Access Configurations
Access for ICs to telephone subscribers within LATA is provided by most LECs as either equal access for conforming end offices or by several other forms of access for nonconforming end offices
4.5.3.1 Equal Access Feature Group
Each LEC must within the terms of the Modification of Final Judgment MN and/or FCC rules provide equal LATA access to all ICs upon receipt of bona flde request
This section discusses the conditions under which access is provided and the network configurations for the access services The transmission plan is described in Section of this document
4-31 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Network Design end Configuration issue April 1994
LATA access is provided through the end offices serving the telephone customer
Originating equal-access FGD service requires the following
trunk-type termination affording call supervision to an IC
uniform access code accomplished using OXXX prefix to be expanded due to
1988 industry consensus to 1O1XXXX prefix dialed by the customer that selects the desired IC
Identification Calling-party identification by forwarding Automatic Number
available as an option to the IC
Recording access-charge billing details
Presubscription to customer-specified IC
Overlap outpulsing
These features can be provided only in SPC-type switching systems and are available with the vendor products used for illustrative purpose in Section of this document
Terminating equal access requires trunk termination to afford call supervision It also requires some form of terminating message recording for proper access-usage billing to the IC
It is required that equal access for terminating traffic be provided coincident with the provision of originating equal access but it may be provided earlier at the discretion of the LEC
via above the end office The MFJ allows the BOCs to provide access switching system level This switching system or FGD access tandem allows small volumes of traffic to various ICs to be economically gathered at the tandem until direct groups with or without overflow to the tandem can be justified between an end office and an IC
Tandem access is designed to provide service transmission and call-blocking probability equal to that of direct end office-POP connections The location of the access tandem is LEC option and is based on economic studies While an access tandem generally will be located in the LATA it serves it is permissible to serve LATA from tandem located in another LATA
The equal-access multifrequency signaling format consists of the calling number and 7- or 10-digit address information The calling number which includes expanded ANI information digits is transmitted first followed by the address digits See Section of this document for details
FGD access service between an end office and an IC POP will be ordered by the IC The service will be provided in cooperation with the IC on an only-route group between the end office and the POP on tandem connecting group between the access tandem and
POP or on high-usage group between the end office and POP with overflow to the access tandem see Figure 4-10 FGD service does not allow more than one access tandem in connection between an end office and POP
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If an IC has multiple POPs in LATA it is assumed that the IC will elect to serve
designated set of end offices from each POP An access tandem serving multiple IC and/or POPs may need to be able to route to an IC based on the incoming end office trunk group as well as by the CAC IC traffic may not be routed from an end office to
more than one POP based on destination address or IC-designated load allocation but may be alternate routed as described later BOC cannot route originating LATA access traffic to POP other than the one designated by the IC
End Office
End Office
End Office
Figure 4-10 Basic Interexchange Carrier LATA-Access Routing Options
An IC with either presubscription or 1OXXX/1O1XXXX access code dialing can specify
that BOC route LATA-access traffic from an end office to more than one POP or on
separate trunk groups to the same POP according to customer-dialed service prefix
indicator 0- 0-i- 01 011 00- or the originating line class of service multiparty coin hotel/motel See Figure 4-11 Such routing is dependent on screening performed by the equal-access end office
The IC will designate that special routing is required by providing an order for each type traffic from the end office of to the designated POP This type of special routing only
applies to originating traffic Depending on the IC order separate routing pattern may have to be developed for each type of traffic Trunk requirements will then be developed each trunk based the for group on combination of traffic types to be routed over it
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End Office
Figure 4-11 Service Prefix Routing
LATA access between given end office and the POPs for all ICs that do not have an only-route trunk group to the end office will be fmal routed through single BOC designated access tandem One of the advantages of tandem routing is that it reduces trunking and routing changes that may occur because of potential shifts of traffic between different ICs In some LATAs due to geographic considerations access tandem capacity limitations facility availability or economic justification the BOC can elect to sector the
LATA into geographic territories each served by separate access tandem Figure 4-12
Each sector would consist of the territory served by the end offices that are subtending an access tandem for the final routing of terminating LATA-access traffic Likewise end offices should be sectored on single tandem for originating traffic but different tandems can be used according to service prefix routing requirements Access tandem sectoring is independent of the homing plan chosen by the ICs for their POPs
At the of first-route request an IC BOC may all of any type of originating equal-access traffic as defmed by service prefix indicator service access code or originating line class of service to POP designated by an IC and alternate-route overflow traffic to second POP The BOC will determine whether this alternate-routing option will be performed at the end office or the access tandem and specify the trunk quantities Figure 4-13
4-34 SR-TSV.002275 BOC Notes on the LEC Networks 1994
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End Office
Figure 4-12 Sectored Routing
End Office Same
Interexchange Carrier
End Office
End
Figure 4-13 Alternate Routing
4-35 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Network Design and Configuration Issue April 1994
end office BOC will accept an individual ICs terminating traffic destined for single
from more than one POP As with the alternate routing for originating LATA-access
It also traffic this permits the IC to route to more than one POP for service protection another eliminates the necessity for an IC to shuttle traffic inefficiently from one POP to for completion to an end office Figure 4-14
There will be LATAs or areas within LATA where there is either no tandem technically
capable of performing the access-tandem function or no tandem at all In such case tandem function the BOC can identify tandem in another LATA to provide the access
Figure 4-15 The network economics access tandem capacity and facility availability
will determine the selection of this type of arrangement
Figure 4-14 Terminating Routing
End Office
LATA Boundary
Figure 4-15 Out-of-LATA Routing
4-36 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Network Design and Configuration
If LATA does not have an access tandem and uses tandem in another LATA for
access traffic the tandem interLATA connecting trunk groups must be connected to the
ICs POP in the LATA to be served that is the originating LATA That traffic cannot be routed to an ICs POP located in the same LATA as the access tandem BOCs can
also use tandem in an adjacent LATA to perform intraLATA switching although it is not LATA-access function
The design blocking objective for FGD LATA access service applies to the GOS between
the end office and the ICs POP irrespective of the routing configuration used The
design blocking objective is specified in tariffs filed and is typically B.O1
If access is provided by an only-route trunk group direct interLATA connecting
between the end office and the IC POP that group is designed to the blocking objective via specified in the tariff for example B.O1 If access is provided an access tandem both
the end office-access tandem tandem connecting group and the access tandem-POP
tandem interLATA connecting group are engineered to B.005 in order to meet the
overall end office-POP objective of B.Ol The provision of high-usage group between
the end office and the IC POP does not change these blocking objectives on the tandem route
High-usage trunk groups can be established between the end office and the POP in
cooperation with the IC when traffic volumes justifr them Standard engineering
procedures should be followed to prove in high-usage group candidates and to determine
the ECCS to be used in trunk-group sizing The tandem-connecting group serves as the fmal group for all LATA-access traffic into and out of the end office It will be shared by all the ICs except those that have direct interLATA connecting groups IntraLATA traffic the office the also be carried this between end and access tandem can on group based on economics The tandem interLATA connecting group serves as the fmal route for an ICs LATA-access traffic between its POP and the end offices served by the tandem
4.5.3.2 Other Access Feature Groups and
Equal-access service FGD is based on particular dialing signaling routing and transmission capabilities at conforming end offices and access tandems Because some end offices do not have the capabilities that permit FGD service to be offered and because some ICs may not need all the capabilities provided with FGD other access services are also offered These services are offered as Feature Groups or as discussed in the following subsections Transmission plans for these services are discussed in Section of this document
4.5.3.3 Feature Group
Feature Group FGA service provides line-side access With this service customer dials an assigned telephone number that connects to specific IC That IC then returns tone or announcement to signal the caller to input additional tone-generated digits of the
4-37 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Network Design and Configuration Issue AprIl 1994
called number Calls can be completed to the called number by the IC seizing an access Traffic line in the called LATA and dialing the number generally on local-call basis to and from the FGA serving office is completed over augmented local-network trunk groups often via intraLATA tandem
4.5.3.4 Feature Group
Feature Group FOB service is trunk-side access where subscriber currently dials
950-O/1XXX access code to reach the IC This service is available from selected end offices that must be capable of 7-digit translation in order to route the call to the proper
XXX-identified trunk group per industry consensus planned to be expanded to XXXX in April 1993 to the selected IC As with FGA upon reaching the IC address digits that is the called number are provided as specified by the IC
While optional rotary dial service and ANT are also available for direct trunking to an IC they may not be available in every office capable of 7-digit translation Direct terminating access is available to designated end offices with proper call-recording via capability Customers in all types of offices can access an IC or be accessed by an IC an FOB access tandem that provides the translation and call-recording function for the end office However customers in certain end offices for example SXS may need to dial l950O/1XXX for access or l950XXXX after April 1993
The combination of high-usage direct thinking with overflow to the access tandem is available to an IC for those end offices capable of direct termination service An intermediate tandem subtending the FOB access tandem can be employed as an alternative to extending FOB access to end offices by either establishing additional access tandems or by rehoming end offices to existing access tandems
The transmission plan performance objectives are less stringent than for equal access and are provided in Section of this document
4.5.3.5 Feature Group
Feature Group FGC is the post-divestiture equivalent of the nonequal-access predivestiture arrangement provided to ATT as well as default carriers or carriers of last resort It retains the predivestiture routing that generally is on direct basis between each end office and an ATT switching system In those cases where the ATT switching system is in the LATA it will be POP If the ATT switching system is in an adjacent or remote LATA ATT has established facility POP and the BOC will route from the end office only to the facility POP The BOC may desire to route traffic via an FGC access tandem on high-usage/final-route basis or first-route basis via the access tandem rather than routing all the traffic directly Alternate routing of originating traffic takes into account end office capabilities and any technical limitations of interLATA billing data Automatic Message Accounting recording through an access tandem ATT must convert their access service to FGD when an end office
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// SR-IS V.002275 BOC Notes on the LEC Networks 1994
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is converted to equal access Most end offices have now been converted so the use of
FGC is diminishing
4.5.3.6 Operator Services
Operator services are provided on those customer calls that require operator handling to
complete the connection for example 0- 00- collect third-number billing manual
credit card calls and manual sent-paid coin and on calls that require operator or
automated assistance for billing after the customer has dialed the called number for example automated credit card and local coin
In general intraLATA operator billing and assistance services are handled on LEC in operator systems These operator systems are integrated tandem switching systems
that are available from various vendors The integration allows operator traffic to be
combined with intraLATA message traffic on tandem connecting trunks between the end
office and the access tandem These systems technically allow the LECs to provide FGC
ICs well for themselves In these tandems and FGD operator services for as as addition
with or without the operator function are capable of switching operator traffic to those
ICs wishing to provide their own operator services In any case the system design provides network economies because normally low volume and inefficiently trunked operator traffic can be efficiently concentrated at tandem Directory assistance and intercept arrangements are described in Section of this document
Sent-paid coin traffic originating from LEC public and semipublic coin stations can be served by LEC operator system for mtraLATA toll calls InterLATA sent-paid coin traffic originating at LEC coin stations is presubscribed to an IC Customer-Owned Coin-Operated Telephones COCOTs do not receive coin box accounting functions from BOC equipment
The trunk facilities between the end office and the OSS are equipped with inband expanded inband or multiwink signaling to provide coin collect coin return and other controls between the LEC operator systems and/or ATT equipment and the coin box
If the coin box control signals are to be tandemed through BOC tandem the tandem must meet the signaling and transmission objectives described in Sections and of this document
FGC traffic identified by 0- or 01 service prefix indicator is predominantly handled by BOC operator system equipment either by operators or by automated means
For those end offices that can sort out intraLATA and interLATA traffic the operator services equipment may be bridged on both IC and BOC tandems so that the IC traffic need not route via the BOC tandem Some LECs may utilize 00- or
1OXXX1O1XXXX-00- to allow separation between IC and LEC 0-operator traffic
Within some independent areas such as Alaska LECs do not and have not provided operator services Within these select areas intraLATA operator billing and assistance services handled via IC third-number are operator systems Ordinarily 0- collect billing manual credit card calls and manual sent-paid coin or calls that require operator
439 BOC Notes on the LEC Networke 1994 SA-TSV-002275 Network Design and Configuration Issue April 1994
assistance are muted to the IC of last resort It is intended that intraLATA 0- traffic is Service Provider the responsibility of the LEC and is therefore routed to an Operator OSP chosen by the LEC All ICs served via an independent areas Equal-Access End
Office EAEO or tandem are accessed by presubscribed customers dialing 00- or 10xxx-00-
Operator services traffic can be combined with 011 and 800 service traffic and
if combined trunk inband with sent-paid coin However on one group signaling requirements will be increased and all trunks will have to be equipped for operator access This requires special trunk circuits and could impact operator system capacity
Combined operation should occur only where the added costs of equipping trunks and the effect on operator system capacity can be offset by reduced trunk requirements
Ordinarily this will occur only where small trunk groups can handle the total traffic volume
Public and semipublic coin station nonsent-paid coin for example credit card service and all noncom-station operator services FGD traffic 0- 01 can be routed to any IC including ATT based on the 1OXXX access code or presubscription Both operator services and Direct Distance Dialing DDD calls with or without the ANI option can calls that be routed directly or via the access tandem However operator assistance-type and are dialed by patron to an IC that has not requested this service may be screened blocked at the originating end office In some end offices customer stations presubscribed to an IC can obtain operator assistance from the IC by dialing 00
4.5.4 Combined Configurations
IntraLATA and interLATA access can be treated as separate network configurations
While such segregation is possible for SPC end offices capable of providing equal-access service there is also the potential to combine the switching and trunking to the extent that network economies can be achieved The following paragraphs discuss typical combined network configurations
In LATAs with single access tandem that tandem can also serve as local intraLATA tandem as shown in Figure 4-16 IntraLATA and interLATA traffic are combined on the tandem connecting trunk groups while the end office-to-end office high-usage groups carry only intraLATA traffic and the end office-IC POP groups carry only interLATA traffic IntraLATA routing is the same as with segregated single-tandem network
Where two or more access tandems are required the tandems can also serve as local tandems in combined sector-tandem configuration as shown in Figure 4-17 As with the single tandem case described above the tandem connecting final groups carry both intraLATA and interLATA traffic The end office-to-end office and end office-distant tandem and the intertandem final intraLATA traffic high-usage groups group carry only routed as with segregated combined sector-tandem configuration
4O SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Network Design and Configuration
High-Usage Trunk Group
Final Trunk Group
Alternate Route
Figure 4-16 Single Tandem/Access Tandem
High-Usage Trunk Group
FInal Trunk Group
Alternate Route
Figure 4-17 Combined Sector Tandem/Access Tandem
4-41 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Network Design and Configuration Issue AprIl 1994
It is feasible to have two access tandems in LATA with only one of them needed as
tandem for intraLATA traffic However this arrangement will normally evolve to the
combined sector-tandem configuration as soon as the thinking rearrangements can be
made to take advantage of the flexibility and multiple alternate routes offered by the
two-tandem arrangement Similarly it is possible that two tandems could be required for
mtraLATA traffic but only one required as an access tandem With only one access
tandem trunking penalties will result from the need to segregate intraLATA and
interLATA traffic to avoid second tandem switch on interLATA calls This can be
avoided by equipping both tandems as access tandems and routing the traffic as shown on
Figure 4-17
The three-level principal tandem arrangement shown in Figure 4-8 may also be used for
intraLATA traffic With this arrangement the sector tandems would be equipped as
access tandems and the principal tandem would function only as tandem for intraLATA
traffic
In LATAs with Dynamic Routing the via nodes serve as tandems and end offices for
intraLATA traffic Due to the one tandem link rule Dynamic Routing cannot currently
be used for interLATA traffic
When the Dynamic Routing algorithm recommends two-link path the probability is
very high that both links will have excess capacity to complete the overflow calls
however there is small probability that one of the two links may not have any spare
capacity to complete the call If the first link is busy the call will overflow to the tandem
and be in completed the same way as it would in hierarchical network However if the
second leg is busy and the A-B call is allowed to overflow from the via node to the tandem then the A-B call will be carried on the three-link path AV VT TB See Figure 4-18 The three-link path however will not cause transmission problems in the
network because the combined transmission loss for links VT and TB or VT Ti and
TB when the offices and home on different tandems and is not greater than that
for the link YB alone The tandem winks and tandem switches are normally designed to make up for the extra transmission loss
Occurrence of such three-link paths can be prevented in the DRT implementation as
follows Two tables be in routing can set up each end office switch one for originating
traffic and for traffic one incoming In switch the originating traffic table should
consist of two paths for V-to-B calls YB VTB The incoming traffic routing table should consist of only one route VB Thus A-B calls which are rerouted from the direct
route AB and reach will attempt YB but if YB is busy they will not overflow to the
VT link The incoming traffic routing table will prevent such overflow On the other
hand V-B calls originating in will attempt YB and if VB is busy they will attempt the VTB path See Figure 4-18
4-42 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Network Design and Configuration
Separate Routing Tables in Via Switches for Originating and Incoming Traffic
A-to-B calls rorouted via
attempt VB but do not over flow through the tandem
Route advance sequence of VB in originating traffic table VB VTB
Route advance sequence of VB in incoming traffic table VB
Figure 4-18 Restricting DRT to Two-link Paths
4.6 Reliability of Equipment and Systems
Local exchange telecommunication networks providing services such as Plain Old
Telephone Service POTS Integrated Services Digital Network ISDN capabilities or future telecommunications services must be highly dependable The customer has come to expect high level of network dependability based on the performance levels that have been experienced for POTS and on the levels that are continuing to be observed for new services such as ISDN
As new technology functionality and services are integrated into the network objectives have been set that at minimum preserve the expected levels of dependability for these existing services
primary characteristic of local exchange network dependability is its availability
Availability is strictly defined as the ability of an item to be in state to perform
function instant required at given of time or at desired instant of time within given time interval This assumes that the external resources if required are provided
4-43 BOC Notes on the LEC Networks 1994 SR-TSV002275 Network Design and Configuration issue April 1994
the However for the intraLATA networks availability is generally interpreted as long- term fraction of time that the network performs its function as intended for example when the network successfully provides communications path from one customer to another
of the intraLATA network There are four major factors influencing the availability as seen by the customer
Network topology
Equipment architectures
Equipment reliability
Telephone company maintenance practices
Each of these factors must be considered during equipment and system design as well as during network planning and design to ensure that an acceptable level of service dependability is provided to customers
To ensure adequate equipment and systems reliability the service dependability includes the management process is followed This process following
Establishment of service-level dependability objectives
Development of reference network architectures
Allocation of the dependability objectives to various facility interoffice etc
network equipment and systems
local network have Baseline service-level objectives on the availability of exchange been developed for network engineering purposes and are presented in this section network- These end-to-end network objectives are derived from long-established and availability objectives observed network-availability performance projected
is and availability needs of the network reference network architecture presented allocations to network segments and network elements are given
These resulting availability objectives for segments equipment and systems are primarily used during network architecture studies product conception engineering where studies design reliability evaluations and customer reliability analyses reliability modeling techniques are used to estimate performance for comparison to objectives In addition they are also used as baseline performance objectives for comparison to actual field performance
4.6.1 Local Exchange Network Hypothetical Reference Connection
The service dependability management process requires reference network architecture or local exchange network Hypothetical Reference Connection HRC The network architecture used as the local exchange network HRC is shown in Figure 4-19
4-44 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Network Design and Configuration
Fadlity
Entrance Entrance
Distribution Distribution
Figure 4-19 Local Exchange Network Hypothetical Reference Connection
Figure 4-19 is simple model of the existing intraLATA POTS network including the major network segments needed to connect two telephone subscribers served by different central office switches There are four network segments used in the HRC
Distribution consisting of two distribution network segments related to each
subscriber customer premises equipment which is not part of the telephone company network is not considered here
Switch the two central office switches
Facility Entrance facility-entrance network segment including equipment such
as analog-to-digital converters channel banks multiplexers automated digital terminals etc
Interoffice the interoffice transmission facility segment used to transmit calls from
one central office switch to the other
4.6.2 End-to-End Network Availability Objective
Since it is important from the customers view that there be high probability of obtaining path through the network high level of end-to-end network availability is desirable This section addresses only the availability of path through the network due to failures of the equipment and not the effects of blocking due to traffic congestion All segments in the network are independent and each network segment contributes directly to the unavailability or downtime of any path The hypothetical reference circuit shown in Figure 4-20 has derived end-to-end availability of 99.93 percent This is approximately 365 minutes per year or one minute per day of unavailability
445 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Issue 1994 Network Design end Configuration April
Facility Facility Entrance Entrance
0.005
Distribution Distribution
99.93%
Figure 4-20 End-to-End Network Availability Objective
4.6.3 Network Segment Availability Objectives
Switching and transmission services and equipment availability objectives are channel Each contributes to traditionally stated in terms of line or availability directly indicate the the end-to-end network path availability Therefore these parameters ability
of the equipment in the network segment to perform its function for example when needed for distribution switching facility entrance or interoffice transmission in each of the customers call Beilcore has investigated the availability of the equipment been network segments shown and end-to-end objectives have proposed to help ensure
is affected the dependability of the services provided over these networks Availability from hardware by many factors such as equipment failures for example resulting and reliability failures software bugs or procedural errors equipment system
architectures maintainability and repair strategies and uncontrollable factors such as and cable cuts/dig-ups storms etc Each factor must be considered in designing
maintaining dependable equipment and dependable network The network segment observed field objectives discussed are based on longstanding performance objectives on p rformance and summation of the objectives for the equipment in the segment Each
network segment is discussed in detail in the following paragraphs
4.6.3.1 Distribution Network Segment
The distribution network segment as used here includes both the feeder and the ioop
from the switch to the customers home/office excluding customer premises equipment Two distribution segments one associated with each subscriber are included in the local
46 SR-TSV-002275 BOC Notes on the LEC Networks 1994
issue April 1994 Network Design and Configuration
exchange network HRC In the distribution network availability is essential from the
telephone customers view since they have come to expect access to the network virtually
that is upon demand The objective on the level of the distribution segment availability
suggested for engineering existing and new services is 99.99 percent see TR-NWT
000499 Transport Systems Generic Requirements TSGR Common Requirements.5
This would give maximum unavailability objective of 0.01 percent which equates to
maximum downtime objective of approximately 53 minutes per year per customer line
Figure 4-21 Availability objectives are sometimes expressed in terms of the
downtime Each is discussed in the complement of availability unavailability or
remainder of this section which is devoted to the switch network segment
4.6.3.2 Circuit Switch
in the interconnection of subscriber lines to trunks The switching systems HRC perform to form the end-to-end transmission path The best method known is the total switch
downtime objective of minutes per year which is described in TR-TSY-000512
Reliability Section 12 module of LSSGR.6 In addition objectives also exist for individual lines 28 minutes per year and for individual trunks also 28 minutes per year For through transmission path transversing the switch from line to trunk the maximum unavailability objective is the sum of the line and trunk unavailabilities minus
minutes per year since the total outage objective is included in both the line and trunk objectives and need only be considered once on through path This results in through-path objective line to trunk of 53 minutes per year or 0.01 percent Switch unavailability is shown in Figure 4-22
Additional dependability objectives have been developed for circuit switches in the following areas and are contained in the LSSGR.1
Cutoff calls
Ineffective machine attempts
Failure rates
Service life
4.6.3.3 ISDN Switch
Reliability objectives for ISDN switching systems have been developed to help ensure that the dependability of ISDN services is similar to that of POTS ISDN introduces the concept of multiple services such as circuit-switched voice and packet-switched data integrated onto the same physical interface Thus the definition of line failure becomes more difficult Therefore parameters that address the numerous partial line outage modes have been developed in addition to objectives of the LSSGR For Basic Rate
Access BRA reliability objectives have been developed to be consistent with Figure
4-22 and the LSSGR Following are examples of new availability downtime parameters
4-47 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Network Design and Configuration issue April 1994
Distribution Network
0.01% mInutes 53 per year
Figure 4-21 Distribution Network Segment Unavailability Objective
Une Trunk -3 mInutes per year Through Path 53 mInutes per year
Une Trunk
28 minutes per year 28 mInutes per year
Through Path
53 minutes per year
Figure 4-22 Switch Network Segment Unavailability Objective Through Path
4-48 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprH 1994 Network Design and Configuration
Total B-channel circuit mode downtime
Total B-channel packet mode downtime
D-channel packet data downtime
Total ISDN circuit switching capability downtime
Total ISDN packet switching capability downtime
for The Similar parameters have been developed Primary Rate Access PRA objectives
can be found in TR-NWT-001047 ISDN Switching System Reliability Objectives for
Basic Rate Access and its supplement for PRA ISDN Switching System Reliability
Objectives Supplement for Primary Rate Access.7
4.6.3.4 Facility-Entrance Network Segment
For purposes of reliability modeling the facility-entrance network segment is defined as
the portion of the network that performs functions such as analog-to-digital and digital-
to-analog conversion framing digital channel cross-connection multiplexing
demultiplexing etc before channels are put onto the interoffice transmission facilities to
be sent to the receiving-end central office At the receiving-end central office it is
assumed that the facility-entrance equipment is replicated to perform reverse functions
such as demultiplexing Figure 4-23 illustrates representative configuration of typical
digital terminal equipment contained in the facility-entrance network The facility-
entrance segment is allocated 0.005 percent unavailability at each end or total of 0.01
percent for both Digital terminals in the facility-entrance network typically have
unavailability objectives of about minutes per year See TR-TSY-000009
Asynchronous Digital Multiplexes Requirements and Objectives8 and TR-NWT-000418
Generic Reliability Assurance Requirements for Fiber Optic Transport Systems9 for more information
4.6.3.5 Interoffice Network Segment
The origin of the availability objective for the BOCs interoffice transmission network is the former Short-Haul Availability Objective which has its origin in early microwave radio applications
The suggested short-haul 2-way transmission minimum availability objective for BOC transmission channel is 99.98 percent 0.9998 availability at 250 miles full
statement of the numeric values of the objective is plot of unavailability linearly prorated by route length However only the maximum Objective will be used here
4-24 is Figure model showing the generic application of the short-haul availability objective to transmission system in the interoffice transmission segment of the network short-haul has been The availability objective widely applied to BOC transmission systems in the past such as fiber-optic systems.59
4-49 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Network Design and Configuration Issue AprIl 1994
Automated
Digltai DSX-1 Digital Terminal DSX-3 Ratho
Interoffice Network
0.005%/ end
or 0.01% for both ends combined
Figure 4-23 Facility-Entrance Network Segment Availability
Transmission System
Line Line
Temilnaling Terminating Equipment Equipment
0.02%
Figure 4-24 Interoffice Network Segment Unavailability Objective
4-50 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue AprIl 1994 Network Design and Configuration
4.6.4 CCS Network Reliability and Unavailability Downtime Objectives
The integration of out-of-band signaling with intraLATA networks via Common
Channel Signaling CCS networks is an important factor in overall network reliability
This is because failures in signaling will prevent completion of calls and will be viewed by customers as failures of the network Following is brief discussion of CCS network unavailability downtime objectives and four potential alternatives to achieve software diversity in the CCS network
control the of time Unavailability downtime objectives are intended to amount CCS network or segment thereof is unable to perfonn its required signaling functions of time They can be represented by single number equal to the long-term percentage
CCS network or segments thereof are expected to be down As such downtime end-user of service The objectives can significantly influence perception quality be either expected percentage of downtime for network element can interpreted as
The average downtime over many years for this network element or as
The average downtime over one year for population of the network elements
National Standard Telecommunications According to ANSI Tl.i 11 American for SS7 MTPIU Section 5.1.2 the Message Transfer Part MTP downtime objective for the
CCS basic mesh network shown in Figure 4-25 corresponds to an average 00 no more than 10 minutes downtime per year for the signaling paths between two Signaling End Points SEPs and is broken down as follows
Each user interface segment should be down an average of no more than minutes
per year
Each network access segment should be down an average of no more than minutes
per year and
The backbone network segment should be down negligible amount of time that is
close to minutes downtime per year Note that downtime for this segment includes
failures that prevent use of the backbone segment but do not by themselves disable
any other segments
The above allocation assumes an ANSI-based Recommendation Ti .111.5 in ANSI
T1.1i1-1988 Section 7.2.110 reference architecture with two-way diversity for the A- link sets and three-way diversity for the B-/D-link sets If three-way diversity is not
The original text in the American National Standard for Telecommunications SS7 MTP refers to
nominal requirements that have been interpreted in TR-NWT-000246 Bell Communications Research
Specification of Signaling System Number 711 as average downtime numbers thus the text in the
parentheses represents Bellcores interpretation of this ANSI downtime objective
Examples of SEPs are Service Control Points SCPs and switches
4-SI BOC Notes on the L.EC Networks 1994 SR-TSV-002275
Network Design and Configuration Issue AprIl 1994
lOmlnutesofdownhfmeperyearMTPonIy
negligible mln/yr minfyr approdmately mIn/yr mm/yr mm/yr
User Network Access Backbone Network Access User
Interface Segment Segment Segment Interface Segment Segment
SEP
Figure 4-25 ANSI Ti .111.6 Downtime Objectives for CCS Basic Mesh Network Segments MTP Only
achievable in the backbone segment the downtime of that segment may no longer be negligible Hence the 10-minute end-to-end objective may no longer be achievable
backbone network segment failure may cause the switches on each Signaling Transfer Point lose communication with the switches the SIP but the Si pair to on remote pair switches can still communicate with the other switches homed on the same Si pair It occurs when
The entire B-ID-link set quad fails
One of the STPs in either mated pair and the B-/D-link set pair of the other Si in the
mated pair fail or
A-link sets to one of the STPs in either mated pair and its C-link set and the B-ID-link
set pair of the other Si in the mated pair fail
When the SEPs in Figure 4-25 are both CCS Switching Offices CCSSOsthe 10- minute end-to-end downtime objective and the above allocation to network segments correspond to single trunk group with its terminating CCSSOs interconnected using the
ANSI-based reference architecture see Figure 4-26
CCSSO is switch equipped with the ISDN User Part ISUP of SS7 for call setup
4-52 SR-IS V.002275 BOC Notes on the LEC Networks 1994 issue April 1994 Network Design and Configuration
10 minutes of downtime per year MTP only
negligible min/yr mm/yr approximately min/yr mm/yr mm/yr
User Network Access Bckbone Network Access User intce Segment Segment Segment Interface Segment STP STP Segment B- or D-link set
ccsso ccsso
mated C-link set C-iink set mated
pair pair hi .fJ B-or D-Iinkset NZV STP STP
One Trunk Group
Figure 4-26 Example Case One Trunk Group with Its Terminating CCSSOs
It also applies when instead of CCSSOs there are Service Switching Points SSPs or SCPs
in Detailed information on CCS network element reliability objectives can be found TR
NWT-000082 Signaling Transfer Point STP Generic Requirements in TR-NWF 000029 Service Control Point Node Generic Requirements for IN1 in TR-NWT
000533 Service Switching Points FSD 31.O1.0000 plus various references.6
An SSP is switch equipped to halt call progress launch an SS7 query to obtain additional information from an SCP and route or treat the call based on the information received in the SCPs response SSPs can be End Offices EOs or tandem switches SSPs interact with databases to provide services and routing
4-53 BOC Notes on the LEC Networks 1994 SR-TSV002275 Issue 1994 Network Design and Configuration AprIl
4.7 Network Service Evaluation
that statistical The Service Evaluation System SES is an operations system provides network indicators that can be used to evaluate the quality of the telecommunications selected call under all types of service conditions Evaluation consists of monitoring no attempts to determine the disposition of the call for example completed busy answer equipment blockages and failures Service evaluation data is used to provide the and to both quality assessment of network service delivered to customer provide direct quality control activities
Service evaluations are random samples of telephone service obtained from the of this function evaluation of calls originated by telephone users Since dropping during times of switch overload would defeat the intent of service evaluation namely to assess customer perspective of service during times when the customer is most likely to be The adversely affected service evaluation is considered nondeferrable function be uniform samples are taken by such means in such quantities and so distributed as to service evaluation throughout BOC network Historically certain switches supported lines interfaces based on the frequent rotation of bridging arrangements among customer raise about However these arrangements are undesirable because they concerns privacy random are costly due to the need for manual rotations cannot provide truly sample
and provide very limited sample size for fault identification Therefore newer interface for switching systems provide some type of common-point monitoring random sampling
link The bridging arrangement or monitoring interface consists of voice link and data
The voice link permits audible monitoring of the call-setup process and the data link
permits the passing of data signals between the switching system and the SES
Network service performance evaluations are completely automated through the use of
the No.2 SES The No.2 SES obtains Dial-Line Service Evaluation DLSE and
Incoming-Trunk Service Evaluation 1TSE measurements without human monitoring TR-TSY-000742.15 See No Service Evaluation System Inreiface
DLSE samples telephone user-originated calls in local office switching systems as close
to the user-origination point as possible It follows the call until an ultimate disposition
is determined Statistics are then accumulated on disposition categories such as completed busy did not answer etc and/or blockage and failure events such as
reorder no ring-no answer etc. This measurement provides an end-to-end view of
service as perceived by the telephone user
methods of manual No SES the first computer-based system for service evaluation automated earlier No remains in evaluation and allowed for centralized operation and automatic record keeping SES Beilcore service to evaluate operator-assisted calls The No SES is the most recent proprietary
software system
44 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue Aprfl 1994 Network Design and Configuration
1TSE used the of the in evaluations are to report on functioning LATA network terminating IC calls Calls may be evaluated at switching systems in the interexchange network and at access tandems As with DLSE statistics are accumulated on various disposition categories This measurement provides view of the performance of the measured switching system and all of its subtending network
In addition to DLSE and ITSE the No.2 SES provides statistics on whether billing information on individual call attempts is being provided correctly by the associated switching equipment and facilities This source of data is called Mechanized Evaluation of Call Completion Anomalies MECCA MECCA provides an automated examination their associated times of sampled call attempts and holding Therefore calls with special remain for than threshold billing types that up longer for example 90 seconds without answer supervision are identified as MECCA calls If answer supervision is not detected which is the switching equipment indicator to allow for the billing of the call to the originating subscriber No.2 SES would classify the call attempt as MECCA failure This information is stored in history file within No.2 SES and reports are issued based on threshold criteria
4.65 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Network Design and Configuration Issue AprIl 1994
46 SR.TSV-002275 BOC Notes on the LEC Networks 1994
Issue ApiiI 1994 Network Design and Configuration
References
FR-NWT-000064 L4TA Switching Systems Generic Requirements ISSGR Beilcore 1994 Edition
FR-NWT-00027 Operator Services Systems Generic Requirements OSSGR Beilcore 1994 Edition
ICCF 93-0729-008 TRS Technical Needs Industry Carriers Compatibility Forum 1993
SR-TAP-000191 Trunk Traffic Engineering Concepts and Applications Issue Beilcore December 1989
TR-NWT-000499 Transport Systems Generic Requirements TSGR Common
Requirements Issue Beilcore December 1993 module of TSGR FR NWT-000440
TR-TSY-000512 Reliability Section 12 Issue Beilcore February 1990 plus
Supplement August 1993 module of LSSGR FR-NWT-000064
TR-NWT-00 1047 ISDN Switching System Reliability Objectives for Basic Rate
Access Issue Beilcore March 1991 plus Supplement August 1991
TR-TSY-000009 Asynchronous Digital Multiplexes Requirements and Objectives Issue Beilcore May 1986
TR-NWT-000418 Generic Reliability Assurance Requirements for Fiber Optic
Transport Systems Issue Beilcore December 1992
10 ANSI T1.1 11-1988 American National Standard for Telecommunications
Signaling System Number SS7 Message Transfer Part MTP American
National Standards Institute 1988
11 TR-NWT-000246 Bell Communications Research Specification of Signaling
System Number Issue Beilcore June 1991 plus revisions
12 TR-NWT-000082 Signaling Transfer Point STP Generic Requirements Issue Bellcore December 1993
13 TR-NWT-000029 Service Control Point Node Generic Requirements for IN1
Issue Beilcore September 1990
14 TR-NWT-000533 Service Switching Points FSD 31-01-0000 Issue Beilcore
January 1994 module of LSSGR FR-NWT-000064
15 TR-TSY-000742 No Service Evaluation System Interface FSD 45-13-0200
Issue Beilcore March 1990 module of LSSGR FR-NW1-000064
.4-57 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Network Design and Configuration issue April 1994
NOTE
document reflects All Beilcore documents are subject to change and their citation in this the most current information available at the time of this printing Readers are advised to check current status and availability of all documents
To obtain Beilcore documents contact
Beilcore Customer Relations
Corporate Place Room 3A-184
Piscataway NJ 08854-4156 1-800-521-CORE
908 699-5800 for foreign calls
BCC personnel should contact their company document coordinator and Beilcore personnel should call 908 699-5802 to obtain documents
To obtain ANSI documents call 212 642-4900
be the Industry Carriers Compatibility Forum ICCF documents can obtained through
Alliance for Telecommunications Industry Solutions ATIS formerly the Exchange
Carriers Standards Association by calling 202 628-6380
48 SR-IS V.002275 SOC Notes on the LEC Networks 1994 Network and Issue AprIl 1994 Design Configuration
Bibliography
American National Standard for Telecommunication Signaling System Number Ameiican National 557Message Transfer Part MTP ANSI T1.111-1988
Standards Institute 1988
Asynchronous Digital Multiplexes Requirements and Objectives TR-TSY-000009 Beilcore Piscataway NJ May 1986
Bell Communications Research Specification of Signaling System Number TR-NWF
000246 Beilcore Piscataway NJ June 1991
Fiber Generic Reliability Assurance Requirements for Optic Transport Systems TR NWT-000418 Beilcore Piscataway NJ December 1992
JSDN Switching System Reliability Objectives for Basic Rate Access TR-NWT-001047
Beilcore Piscataway NJ March 1991
LATA Switching Systems Generic Requirements LSSGR FR-NW1-000064 Beilcore
Piscataway NJ 1994 Edition
No Service Evaluation System Interface FSD 45-13-0200 TR-TSY-000742 Beilcore
Piscataway NJ March 1990
Operator Services Systems Generic Requirements OSSGR FR-NWT-000271 Beilcore
Piscataway NJ 1994 Edition
1990 Reliability Section 12 TR-TSY-000512 Beilcore Piscataway NJ February
Service Control Point Node Generic Requirements for INJ TR-NWT-000029 Beilcore
Piscataway NJ September 1990
Service Switching Points FSD 31-01-0000 TR-NWT-000533 Beilcore Piscataway NJ
January 1994
Signaling Transfer Point STP Generic Requirements TR-NWF-000082 Beilcore
Piscataway NJ December 1993
Transport Systems Generic Requirements TSGR Common Requirements TR-NWT
000499 Beilcore Piscataway NJ December 1993
TRS Technical Needs ICCF 93-0729-008 Industry Carriers Compatibility Forum 1993
Trunk Traffic Engineering Concepts and Applications SR-TAP-000191 Beilcore
Piscataway NJ December 1989
4-59 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Network Design and Configuration issue April 1994
440
SR-TSV-002275 SOC Notes on the LEC Networks 1994 Issue AprIl 1994 Contents
Section
Billing Customer Data and Control Contents
Billing Customer Data and Control 5-1
5.1 Automatic Message Accounting 5-1
5.1.1 Data Generation...... 5-3
5.1.1.1 FlatRate alls ...... 5-3
5.1.1.2 Measured-Rate Calls.... 5-3
5.1.1.3 Toll Cals ... 5-4
5.1.1.4 InteiLATA Carrier Interconnection 5-4
5.1.1.5 Originating-LATA Recording of Interexchange
arrier/International arrier alls 5-4
5.1.1.6 Terminating-LATA Recording of Interexchange
Carrier/International Carrier Calls 5-6
5.1.1.7 Advanced Intelligent Network Automatic Message
Accounting...... 5-6
5.1.1.8 Centralized Automatic 5-7 Message Accounting ....
5.2 Netsvork Service Evaluation ...... 5-7
5.3 Customer Network Services 5-8
5.3.1 Message Detail Recording 5-8
5.3.1.1 MDRv1aRAO...... 5-9
5.3.1.2 I11R to Customer Premises .... 5-10 5.4 Customer Network Ivlanagement 5-10
5.4.1 Configuration ls4anageinent...... 5-11 5.4.2 Perforniance Management 5-12
5.4.3 Fault Management...... 5-14
5.4.4 Accounting Management..... 5-15
5.4.5 Security Management...... 5-16
R.eferences ...... 5-17
Bibliography 519 BOC Notes on the LEC Networks 1994 SR-IS V.002275 Contents Issu April 1994
II SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprU 1994 BUling Customer Data and Control
Billing CustomerData and Control
This section discusses the many features that define and maintain billing customer data and control
5.1 Automatic Message Accounting
Automatic Message Accounting AMA is the process used by circuit-switching systems packet-switching systems and other network elements to provide certain type of data
This data is needed either to permit charging the customer for use of network services or to permit charging Interexchange Carriers ICs for access to the Local Access and Transport Area LATA network for their end users and optimally to facilitate their billing to these end users The specific data items needed for customer billing are determined by complex interaction between the customers service request the customers service permissions and local tariffs
In general network personnel create and maintain the databases about customer service permissions and charging in response to service orders issued when customer requests involve interaction between new or changed service In todays network such requests the customer and Local Exchange Carrier LEC service representative Special direct interactions between the customer and network elements and/or Operations-Support
Systems OSSs could commonly initiate service changes in the future
Network elements determine what service to provide by using customers service request for example dialed digits and the networks database information about the customers service permissions Then by using AMA call processing these elements determine whether usage information must be generated for billing and other purposes
If AMA data is generated the network element outputs the data in form suitable for processing by Revenue Accounting Office RAO
The AMA data output from the network element is transported to the RAO by AMA teleprocessing data networking or via magnetic tapes These tapes are carried between the network element and the RAO network element that is provided with an AMA teleprocessing feature transmits AMA data on store poll and forward basis to central point for input into the RAO message billing process The teleprocessing feature is implemented at the network element via hardware and software which as package is called an AMA Transmitter AMAT An AMAT is connected to central collector through data-transmission facilities to form an AMA Teleprocessing System AMATPS more information see TR-TSY-000385 Automatic Message Accounting Teleprocessing System AMA TPS Generic Requirements.1
AMA data networking like AMATPS allows transmission of AMA data to central point for input to the RAO In particular AMA data networking takes advantage of emerging data services and file transfer protocols for the information transport AMA
Data Networking System AMADNS supports the transfer processing and management mechanisms required to supply data applications with AMA data Although similar mechanisms are provided by the AMATPS which is the system currently used for AMA
5-1 BOC Notes on the LEC NetworksI 994 SR-TSV.002275 1994 Billing Customer Data and Confrol Issue AprIl
which data transfer the future environment dictates that mechanisms be supported are considerably more advanced than the present ones The future environment will see substantially higher AMA data volumes due to new network services and more- comprehensive measurement strategies for existing services At the same time new and of these will have applications will require access to AMA data some applications data and near-real-time and on-demand special needs such as specialized processing access to AMA data In addition the value of given AMA data may vary widely due to the use of data aggregation for example thereby requiring the capability to treat different AMA data in different manner Because AMATPS will not be able to adequately support this future environment the concept of an AMADNS has been developed AMADNS is designed to support the anticipated AMA data volumes and while the of special needs of multiple applications retaining high degree quality for data Generic availability and security required AMA See GR-1343-CORE
Requi rements for the Automatic Message Accounting Data Networking System AMADNS for more information.2
The AMA data records received in an accounting office are edited and subjected to various integrity checks The Customer Record Information System CRIS processes
in this is to records that are needed for end-user billing The first major step processing for each billable of calculate monetary price based on applicable tariffs occurrence customer usage The corresponding customer account is recognized and the priced usage transactions are posted for customer billing at regular intervals Records that are needed for carrier access billing are sent to the Carrier Access Billing System CABS which
based the to the calculates monetary prices on applicable tariffs posts resulting charges carriers accounts and bills the carriers on regular basis CRIS and CABS are generic of There terms used to describe specific types billing systems are currently many system types that are based on the CRIS and CABS general functionality but have different names The names of the billing systems may be different but they all perform basically the same function
In addition to using the AMA data for actual billing purposes the data is also used for network and surveillance For these such ancillary functions as maintenance operations functions the data received by the RAO in the normal AMA data stream is spun-off for dissemination to the organization requesting the data
Because of the tremendous volume of AMA data that typical LEC accounting offices must process each day and the business requirement for very high integrity billing network processes it is essential that universal AMA data format be used by all elements and for all services This format is referred to as the Beilcore AMA Format
for all services are set forth in TR-NWT BAF The generic requirements of BAF 001100 Belkore Automatic Message Accounting Format BAF Requirements.3 Similar generic requirements for other services are documented in Beilcore documents for the specific service
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5.1.1 Data Generation
Every line and/or trunk that can originate LEC service is assigned charge class This
charge class in conjunction with other supplementary data determines the service
from the line and/or trunk The class is also requests that can be originated charge
factor in determining whether or not an AMA data record is to be generated for given
service request and in determining the content and format of AMA data generated for the
service request
For each occurrence of service use AMA data is generated if that use is billable or if the
data is required for one of the ancillary AMA data-usage functions The AMA data is
under the that all of associated with the service always provided premise usage resources
may be billable Therefore in addition to data input that is common to all AMA data records for example the identification of the user of the service the users service
requests dialed digits the time and duration of such use the record for specific network
service use contains data specific to that use and the features of the customers line or
trunk that provide access to the service
The following sections discuss AMA data generation strategies for several services and technologies These sections do not cover all types of recordings see TR-NWT-001 10 for complete list
5.1.1.1 Fiat-Rate Calls
fiat-rate area is defined by group of destination codes called NXX or NPA-NXX and usually includes all the destination codes within geographic boundary flat-rate
service permits non-coin line customers having the appropriate charge class to make for
fixed monthly charge an unlimited number of network uses of services or calls to destinations within flat-rate area
For calls originated from lines having the flat-rate charge class AMA data is normally not required for call to destination within the originators flat-rate area However for individual and multi-party lines capability is provided to generate detailed AMA data for special studies and for billable features that may apply
5.1.1.2 Measured-Rate Calls
Measured-rate service provides to customers who have the appropriate charge class limited amount of call usage to destinations within defined message-rate area for basic monthly charge All usage for calls to destinations within the defined area that exceeds the limit is additionally charged Computation of the allowed and additional usage may be based upon any combination of the following factors distance called call duration time of day day of the week and/or date
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The data generated for local message-rate calls is formatted into message-rate call type data for call The particular call type to be used for recording the AMA billing particular is function of the data that is necessary for the billing tariffs that determine the charges for that call
5.1.1.3 Toll Calls
flat-rate and/or Calls to destination codes outside the originating customers message-rate area are chargeable mainly on the basis of the call destination the call duration the day the date and the time of the day For nonoperator-handled calls originated by 1- and
in the 2-party non-coin lines the AMA data record is generally generated switching
is function of office serving the originating customer The actual form of the record how the call is to be carried for example via the Bell Operating Company BOC facilities or those of an IC domestic carrier or International Carrier For calls that
centralized for originate from 4- or 8-party lines the call must be routed to point
for these calls is made at that identification of the calling station The AMA data record point
As competition for carrying intraLATA traffic increases for the BOCs other suppliers may become toll call carriers If this situation occurs then that supplier will be required in to perform the same AMA billing as the BOCs This AMA billing may or may not be decide BAF It will be up to that supplier and the Public Utilities Commission PUC to on the best method to ensure correct billing and system continuity
5.1.1 InterLATA Carrier Interconnection
Per-call AMA data records are generated at each LATA for all IC/INC calls originating from or terminating to that LATA This includes calls routed to an operator-service facility and test calls made by an IC/INC to LATA
As mentioned previously in Section 5.1.1.3 the BOCs will not be the only carriers providing intraLATA service The originating and terminating records that are currently generated may have to be changed The change will be based on the premise that the IC/INC the call not or may carry end-to-end thereby requiring separate originating terminating record Other changes may be made in order to ensure correct billing The best solution will be up to the IC/INC and the PUC
5.1.1.5 Onginating-LATA Recording of lnterexchange Carrier/international Carrier Calls
records and The following describes two types of records per-call AMA data originating-LATA overflow records
Per-Call AMA Data Records In multifrequency signaling environment an where the originating-call AMA record is made for all calls that progress to the stage
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carrier-connect signal is received from the IC/INC The time at which the leading
edge of this carrier-connect signal is received from the IC/INC is used as the carrier-
connect time for the originating LATA
For Common Channel Signaling/Signaling System CCSISS7 the Initial Address
Message lAM is sent directly from the Signaling Point/Service Switching Point
SP/SSP end office to the IC/INC to start timing If an access tandem switch is involved in the call then the Exit Message EXM sent from the access tandem to the
end office SP/SSP indicates that the call setup information has actually been sent to
the IC/INC
In either the multifrequency or the CCSISS7 case the AMA data record contains
called-party answer time as well as the carrier-connect time In addition the AMA
data record contains the identity of the carrier that is dialed or the presubscribed
carrier The elapsed time from answer time to disconnect is used for billing the
customer for the call the elapsed time from carrier-connect time to disconnect is used
for billing the ICIINC access charges
Calls to an IC/INC operator-service facility are handled differently An access record
is generated at the Equal-Access End Office EAEO for calls routed directly to an
IC/INC operator-service facility Since called-party supervision is not passed back to
the EAEO these calls generate unanswered call records whereby the call disconnect
time for carrier-connect elapsed-time calculations is determined at the time of
operator release
Originaring-LATA Overflow Record AMA data records are generated for calls that
reach the point where the carrier-connect signal is received AMA records are also
generated to provide count of the number of calls that cannot be delivered to the
ICIINC because an outgoing trunk is not available
This overflow record is generated every hour and is output only at the originating
LATA For an IC/INC with only direct connection from the EAEO the overflow
count is incremented whenever call cannot be delivered to the IC/INC because an
outgoing trunk is not available For an IC/INC with both direct connection from the
EAEO and an overflow connection to the access tandem no count of calls that
overflow to the access tandem or calls that are blocked direct and tandem-connection
busy is made at the EAEO An overflow count is incremented in the hourly record
generated at the IC/iNC access tandem for calls that do not complete because an outgoing trunk is not available from the access tandem to the IC/INC
The generation of this record is based on the premise that the BOCs will be handling
the intraLATA call Since competition for intraLATA call traffic has increased the
BOCs will not be the only carriers There may be other carriers of intraLATA traffic
that do not require this record It should be noted that another type of records may be needed to address the new intraLATA carriers
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5.1.1.6 Terminating-LATA Recording of Interexchange Carrier/International Carrier Calls
The switching system at which the call enters the LATA generates the terminating AMA access record per-call access record may be made for all calls that progress to the where seizure from the IC/INC has been In stage an incoming-trunk signal recognized all records the leading edge of this seizure signal is used to determine the recorded carrier-connect time for the terminating LATA However only the elapsed time from
the ICIINC called-party off-hook time to call disconnect time is used for billing access charges
The generation of this record is based on the premise that the BOCs will be handling the intraLATA call Since competition for intraLAlA call traffic has increased the BOCs will not be the only carriers There may be other carriers of intraLATA traffic that do not require this record It should be noted that another type of records may be needed to address the new intraLATA carriers
5.1.1.7 Advanced Intelligent Network Automatic Message Accounting
With the advent of Advanced Intelligent Network AIN the traditional forms of AMA data will change to some degree This change will come in the form of enhanced services that wifi allow the SSP end office to generate AMA records for new services without needing generic update for the new feature This is accomplished by the AIN Expanded
Call Model ECM which allows the BOCs to design new feature and specify the desired AMA data format to be generated by the SSP end office This flexibility allows the BOCs to customize the billing of the new feature based on the BOCs current billing formats and applicable tariffs This method expedites the previous method in which the
BOC would go to the supplier and request the design of new feature The supplier would in turn design the AMA data format to Beilcores or the suppliers own specifications and then return the completed feature to the BOC for approval The requesting BOC had very little control over the design and AMA data format of the new feature With AIN AMA the requesting BOC has complete control utili7ing the AIN
ECM to design the AMA data format to its unique specifications
AIN performs its functions via the CCSISS7 network When an AIN feature is activated the SSP end office sends database Service Control Point which in query to the SCP turn looks up the requested information in its database and sends reply message back to the SSP The SSP then decodes the message processes the call and performs any SC indicated function in this case the appropriate AMA data is generated In summaiy the
SC is typically the main source of information not the SSP This allows for greater
AMA data format flexibility for the design and implementation of new customer-focused features
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5.1.1.8 Centralized Automatic Message Accounting
The AMA data for certain calls is controlled collected and recorded at Centralized
Automatic Message Accounting CAMA recording location These calls may originate that does have the Local Automatic from local switching system not Message
Accounting LAMA feature Or these calls may originate from those lines of local that has the feature but the switching system LAMA cannot automatically identify
directory number of the originator for example those calls originated by 4- and 8-party
lines served by the local switching system Hence the calls must be connected to an
operator for manual identification and input of the originating-station directory number
The switching system having the CAMA recording function is typically tandem switching system which is equipped with the AMA features The tandem switching system is also equipped with the Automatic Number Identification AN1 and Operator
Number Identification ONI features For operation with CAMA the local Stored
Program Control System SPCS should be capable of outpulsing the calling-line identity
of lines requiring ANI of the originating number AMA data recorded at CAMA
recording location is in general identical to that recorded at LAMA recording location
5.2 Network Service Evaluation
The Service Evaluation System SES is an operations system that provides statistical
indicators that can be used to evaluate the quality of the telecommunications network
under all types of service conditions Evaluation consists of monitoring selected call
attempts to determine the disposition of the call for example completed busy no answer equipment blockages and failures Service evaluation data is used to provide
both quality assessment of network service delivered to the customer and to direct quality
control activities The service evaluation process as utilized by the BOCs is defined in more detail in TR-TSY-000541 Measurements azdAdministration4 Section 8.4 of
FR-NWT-000064 LATA Switching Systems Generic Requirements LSSGR.5
Service evaluations are random samples of telephone service obtained from the evaluation of calls originated by telephone users Since dropping of this function
during times of switch overload would defeat the intent of service evaluation namely to
assess the customer perspective of service during times when the customer is most likely to be adversely affected service evaluation is considered nondeferrable function The
samples are taken by such means in such quantities and so distributed as to be unifonn throughout BOC network
Historically certain switches supported service evaluation interfaces based on the frequent rotation of bridging arrangements among customer lines However these arrangements are undesirable because they raise concerns about privacy are costly due to the need for cannot manual rotations provide truly random sample and provide very limited sample size for fault identification Newer switching systems provide some type of common-point monitoring interface for random sampling
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The bridging arrangement or monitoring interface consists of voice link and data link
The voice link permits audible monitoring of the call-setup process and the data link
permits the passing of data signals between the switching system and the SES
Network service performance evaluations in use by the BOCs are completely automated
through the use of the No.2 SES.5 The No.2 SES obtains Dial-Line Service Evaluation DLSE and Incoming-Trunk Service Evaluation 1TSE measurements without human
monitoring see TR-TSY-000742 No Service Evaluation System Interface.6
5.3 Customer Network Services
Customer network services provide data to customers concerning the customers use of the LEC facilities and services This data may be used by the customer for such purposes
as cost allocation and private telecommunications network management Although large
business and government customers are the typical users these services are not restricted to such customers the services may also be used by other business and residential customers
Currently only one service Message Detail Recording MDR defined as customer
network service is widely deployed However to meet the customers needs for
additional data concerning the customers use of LEC facilities and services other services may be offered on local basis now or widely in the future
5.3.1 Message Detail Recording
The MDR feature provides detailed data on customers calls The primary user of
MDR information is the business customer As required by the MDR customer the
switch may provide MDR call data for calls originated by the MDR customer for
example from the customers line private facility trunk attendant etc and/or calls
terminating to the MDR customers facilities for example private facility trunk
attendant etc. The MDR customer typically uses the call data records for cost
allocation and/or telecommunications system management MDR has evolved to become
an umbrella term to describe the recording of usage information for features such as authorization account or codes queuing automatic route selection facility restriction
private facility access etc In the past the MDR feature was broadly termed Station
Message Detail Recording SMDR
Various features in currently deployed switching systems provide the capability for the
switching office to provide records of call details to customer However GR-610-
No.1 SES the first computer-based system for service evaluation automated earlier methods of manual
evaluation and allowed for cenalized operation and automatic record keeping No SES remains in
service to evaluate operator-assisted calls
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CORE Message Detail Recording MDR specifies two basic methods for providing MDR data7
One method the MDR via the RAO feature provides capability for transmitting MDR information to the BOC RAO in the same data stream that transmits AMA data records for the switching system As the RAO processes the received data stream the MDR the data records and forwarded to the AMA information is separated from all AMA customer
An alternative method provides MDR to the customers premises whereby the switching call the data system that serves the call forwards the MDR data for the to customer on link or its equivalent
5.3.1.1 MDRviaRAO
Two methods are available to transport the customers MDR data as part of the AMA file With the first method MDR data is derived by RAO processes generally from the AMAdataforacall ThesourceofthedataistheactualAMArecordinthecasewhere an AMA data record is generated for billing purposes This AMA data record serves the dual role for billing the call and for MDR purposes Therefore RAO processing has to recognize from the AMA record data itself for example originating number etc that MDR data must be derived from AMA data However if no AMA data record is generated for the call such as when call uses only private customer facilities the switching system generates special record that is used for MDR data purposes only
file with all These special records are recorded in the switching systems AMA along other AMA data records
The second method for transmitting the MDR data to the customer via the RAO
record whenever data is to be for call generates separate MDR data MDR provided
Therefore if the call is chargeable two separate records are generated for the call the
AMA data record and the MDR data record This arrangement has limited use only and is not consistent with GR-6 10-CORE generic requirements These MDR-data-only records are also inserted into the AMA data record stream for transport to the RAO
The BAF modular concept supports more efficient method of providing MDR data via the RAO Instead of creating two records for an MDR customers calls an MDR record and an AMA data record one record can be used for both purposes MDR data modules defined in GR-610-CORE are added to existing AMA data records to record
is otherwise the information needed for MDR data purposes only that not part of AMA data record
Regardless of which method provides MDR data via the RAO the MDR data is output from the network element in the AMA data stream This data is transported to the BOC
that hand-carried between the network element and the RAO either by magnetic tapes are
RAO or via AMA teleprocessing AMA teleprocessing is switching system feature to transmit AMA data on store poll and forward basis to central point for input into the
RAO message billing process RAO processes separate the MDR customer-required data
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fromthe AMA ca data whetherthe MDRdatais in the same record as the call data or
in separate record reformat the MDR data into the form required by the customer for
example magnetic tape printed reports etc and forward the MDR data to the MDR customer
5.3.1.2 MDR to Customer Premises
If the customer MDR data is to be transmitted by the switch to the customer premises
currently deployed switching systems must generate two different data record types to
provide both MDR data to the customer as well as AMA data to the RAO One type
transmits the AMA datain the AMA file if the call is billable orotherwise requires an
AMA data record and another transmits the MDR data directly to the customer
To further simplify the MDR data generation whether for MDR via RAO or for MDR to
customer premises the modular record is designated for transmission of the MDR data in
either case By using the modular AMA data record for MDR purposes the AMA data record enhanced with the MDR-speciflc data modules forms the 1DR data record As previously stated in those cases where the MDR data is to be transported to the customer via the RAO the MDR data modules are included in the AMA data record that is transmitted to the RAO However if the MDR data is to be transmitted to the customer in some manner outside of the MDR-via-RAO stream for example MDR to customer premises the MDR data modules are included only in the MDR data record sent to the customer the normal AMA data record if required for the call is transmitted to the
RAO without the MDR data-specific modules
The MDR-to-customer-premises data record generated at the switching system is transmitted from the switching system toward the MDR customers Customer Premises
Equipment CPE The MDR data flow is entirely from the switching system toward the
CPE however control messages may be exchanged between the CPE and the switching system The transmission facility is provided by BOC-offered service that may be analog private line message telephone service using dial-in/dial-back arrangement for security purposes digital data system channel Public Packet-Switched Service
PPSS or Integrated Services Digital Network ISDN access TR-NWT-000499 Transport Systems Generic Requirements TSGR Common Requirements.8
5.4 Customer Network Management
The offer of Customer services for the BOCs variety Network-Management CNM exchange and exchange-access networks These services provide customers access to and control over the BOC facilities and services that they use Large businesses government customers and ICs are typical users of these services
CNM supports five major management functions
Configuration management
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Performance management
Fault management
Accounting management
Security management
Beilcore and Each BOC uses unique variety of systems developed internally often by third-party vendors to support its marketing strategy Therefore not all of these functions are available in all BOCs
5.4.1 ConfIguration Management
Configuration management applies to variety of network services including but not limited to switched voice switched data and packet data The following examples illustrate some of these functions
Centrex Reconfiguration customer can modify Centrex/station features such as
the another stations capability to remotely pick up incoming call or rearrange Centrex lists also known as swap telephone numbers which allows the customer
to change station numbers
Private-line Reconfiguration Allows customers to allocate resources by reserving
lines verifying resources combining bandwidth across contiguous channels and
defining special days for temporary reconfigurations These functions may apply to
analog private lines Digital Signal level DSO and below or DS1 and above
also review information customer may routing or current routes past routing changes and scheduled muting changes
customer has four routing controls
Change muting for specific duration or until further notice
Manage routing preferences
Rename routes
Take mutes out of service and restore them to service
Service Order Management customer can perform the following six functions
Initiating service order allows customer to submit service order
Checking service order status enables customer to request information about
the status of service order which may include the following service order
receipts the planned completion date actual completion date and price quotes
Receiving notification permits the management system to notify the customer
proactively when information becomes available for example when the order is completed
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Modifying service order allows customer to access pending service order
and modify it
Canceling service order permits customer to request that pending service
order request be canceled
Cross-referencing related service order numbers lets customer look up which
service orders are related to one another
existence Directory Number Hunt Groups DNHGs customer may control the
and membership of DNHGs by four specific functions
Creating or deleting DNHG
Adding or removing DNHG member
Examining the current status of DNHG
Cross-referencing all DNHGs and Centrex lines
Network Planning Access Information customer may acquire information about
available facilities the capacity of facilities and the compatibility of facilities
Service Information This poition of configuration management provides information to customer For example customer may request list of circuits and
telephone numbers that describes their services customer may also use this service function to find the name of trouble circuit for reporting purposes verify
information before taking further actions such as entering trouble and check the
consistency of information between the customers records and the actual network
5.4.2 Performance Management
Performance management consists of traffic-measurement reporting and performance functions monitoring Traffic-measurement reporting comprises seven
Receive Scheduled Traffic-Measurement Report customer may access
traffic-measurement reports that have been previously scheduled as they become
available
Request and Receive On-Demand Traffic-Measurement Report customer may
request on-demand traffic-measurement reports and access them when they become available
List All Requested Reports customer may receive listing of outstanding
traffic reports
Create and Modify Schedule for Traffic-Measurement Reports customer may
set the schedule that determines when traffic measurements are taken for example
each day at midnight every 12 hours
Create and Modify Traffic-Report Definition customer may initiate traffic-
report request by defining the information that the report should provide for example traffic over half-hour period
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Modify Filters for Traffic-Report Delivery customer may set filter criteria to
control which requested reports are actually delivered or when they are delivered
Cancel Traffic-Measurement Request customer may cancel previously requested on-demand or scheduled report
The second of is similar to fault part performance management performance monitoring management The two differ in that fault management is concerned with managing performance degradations that affect customers service for example as defined in tariff while performance monitoring refers to functions that allow customers to obtain evaluate and report on network performance parameters in less severe deterioration cases Some of these functions are described below
Real-Time Performance Monitoring Performance information passes through
filter of criteria to determine what alarms should be sent to the customer Information
is sent to the customer as quickly as normal system processing permits
Real-Time Performance Criteria Modification customer may modify the criteria
that are used to filter performance information
Performance Data Logging Performance information may be placed into log file
for customer access The specific data that is recorded in this log is determined by second ifiter that contains criteria that may be different from those used in the filter for real-time performance monitoring
Performance Data Logging Criteria Modification customer may modify the
criteria that are used to filter performance data for the log file
Performance Log Retrieval customer may request in whole or in part performance log For example customer may request all logged performance data
for specific circuit in specific time period
Current Status Request customer may request on-demand status reports for facilities and access them when they become available
Scheduled Status Report Retrieval customer may access previously scheduled
status reports for facilities when they become available
All Requested Reports customer may receive listing of all outstanding status reports
Schedule Creation and Modification customer may create view and update
the schedule for recurring scheduled status reports
Parameters Creation and Modification customer may create view and
update parameters controlling the content of scheduled status report
Status Request Cancellation customer may cancel previously requested
on-demand or scheduled report
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5.4.3 Fault Management
Fault management comprises alarm surveillance testing and trouble administration
Alarm surveillance is concerned with managing information about service affecting performance degradations
Real-Time Alarm Reporting Alarm information passes through filter of criteria
to determine what alarms should be sent to the customer Information is sent to the
customer as quickly as normal system processing permits
Real-Time Alarm Criteria Modification customer may modify the criteria that
are used to filter alarm information
Alarm Logging Alarm information may be placed in log file for customer alarms that recorded in this determined second access The specific are log are by filter that contains criteria that may be different from those used in the filter for real time alarms
Alarm Logging Criteria Modification customer may modify the criteria that are
used to filter alarms for the alarm log file
Alarm Log Retrieval customer may request an alarm log in whole or in part For example customer may request all logged alarms for specific circuit in
specific time period
Testing applies to analog and digital interfaces The seven functions that follow describe aspects of testing
Test that be done Request Scheduled customer may request test at some
point in the future or at regular intervals at certain time This function allows
customers to execute intrusive tests of analog facilities that would otherwise
interrupt their service
for List All Scheduled Tests customer may request list of all tests scheduled
given facility or facilities
Modify Schedule of Test customer may access and modify request for
scheduled test
Request On-Demand Test customer may request that test be performed as
soon as possible
Request Test Cancellation customer may request that scheduled or on-
demand test be canceled Because of information-processing delays by the
network provider cancellation request does not necessarily mean that the test
will actually be canceled
Receive Test Results customer may be notified that test is complete This
notification may be accompanied by test results or the customer may be required
to take specific action to receive the results This function applies both to
scheduled and on-demand tests
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be The Set Test Type customer may request that specific test performed
customer may also be permitted to set parameters for the requested test In some
cases the customer may not be given the option of setting test type or parameters These may be automatically assigned according to the facility being tested
The last area of fault management is trouble administration Trouble administration also has seven functions
Enter Trouble customer may request that trouble report be created with the
appropriate information
Add Trouble Information customer may provide additional descriptive tests information will be to the for an open trouble report This additional appended entered description provided when the trouble was originally
Cancel Trouble customer may attempt to close out trouble report
Typically the customer has resolved the trouble and wants to abort the trouble
report
Check Trouble Status customer may request status information on an open or closed customer trouble report
Review Circuit Trouble Histoiy customer may request information about past
troubles reported for particular service or circuit
Report Trouble Status Change customer may be notified proactively of
changes in the trouble status
Request Trouble Report Format customer may request information on what circuit conditional package of attributes applies to trouble reports for particular or service
5.4.4 Accounting Management
customer may access two classes of accounting information
As rendered for example as they appeared on the bill
Current information based upon the current billing period
Accounting management has six functions
Get Billing Information customer may request accounting information This
request may be defined for the current or rendered billing period for one or more billing details or as summary of billing information
Reconcile Billing Concerns customer may request that an accounting item be
verified for accuracy
Manage Billing Information For example billing numbers telephone numbers
cross-references limits
5-15 SOC Not. on the LEC Network 1994 SR.TSV-002275 Issue 1994 Billing Customer Data and Control April
Notice of Exceeded Limits customer may be notified if monetary limit has been exceeded This limit may be prespecified by the customer or network provider and may pertain to single user or group of users
Bill Payment customer may provide information in support of bill payment
Usage Data customer may access infonnalion on service usage for example
Switched Multi-megabit Data Service reports
5.4.5 SecurIty Management
ensured Security regarding access to and control of customers services and facilities is through seven functions
Authentication Customers should verify their identities to gain entry to access
and control mechanisms
Paititioning customer may not be permitted to manipulate services and
facilities that are servicing other customers
Data Jntegrity customers data is protected from unauthorized changes
Data Confidentiality customers data is protected from eavesdropping
Intrusion Detection and Recovery Methods are provided to detect intrusion and
undo any unauthorized changes
Administration The customer may share responsibility for determining security levels and user permissions
Reporting The customer may receive reports of unauthorized or suspicious
activities
5-16 SR-IS V-002275 SOC Notes on the LEC Networks 1994
Issue AprIl 1994 Billing Customer Date and Control
References
TR-TSY-000385 Automatic Message Accounting Teleprocessing System
AMATPS Generic Requirements Issue Beilcore September 1986 plus
Revision February 1990
GR-1343-CORE Generic Requirements for the Automatic Message Accounting
Data Networking System AMADNS Issue Beilcore February 1994
TR-NWT-001 100 Belkore Automatic Message Accounting Format BAF
Requirements Issue Beilcore February 1993 plus revisions
TR-TSY--000541 Measurements and Administration Issue Beilcore July 1987
plus bulletins and revisions module of LSSGR FR-NWT-000064
FR-NWT-000064 JATA Switching Systems Generic Requirements ISSGR Beilcore 1994 Edition
TR-TSY-000742 No Service Evaluation System Interface FSD 45-13-0200 Issue Beilcore March 1990 module of LSGR FR-NWT-000064
GR-6 10-CORE Message Detail Recording MDR FSD 02-02-1110 Issue Beilcore October 1993 module of LSSGR FR-NWT-000064
TR-NWT-000499 Transport Systems Generic Requirements TSGR Common Requirements Issue Beilcore December 1993 module of TSGR FR NWT-000440
NOTE
All Beilcore documents axe subject to change and their citation in this document reflects the most current information available at the time of this printing Readers are advised to check current status and availability of all documents
To obtain Beilcore documents contact
Beilcore Customer Relations
Corporate Place Room 3A-184
Piscataway NJ 08854-4156 1-800-521-CORE
908 699-5800 for foreign calls
BCC personnel should contact their company document coordinator and Beilcore personnel should call 908 699-5802 to obtain documents
5-17 BOC Notes on the LEC Network 1994 SR-TSV-002275 1994 Billing Customer Data and Confrol Issue AprIl
5-18 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 BIlling Customer Data and Control
Bibliography
Automatic Message Accounting Teleprocessing System AMA TPS Generic Requirements TR-TSY-000385 Beilcore Piscataway September 1986
Belicore Automatic Message Accounting Format BAF Requirements TR-NWT 001100 Beilcore Piscataway NJ February 1993
Generic Requirements for the Automatic Message Accounting Data Networking System AMADNS GR-1343-CORE Beilcore Piscataway NJ February 1994
LATA Switching Systems Generic Requirements ISSGR FR-NWT-000064 Beilcore Piscataway NJ 1994 Edition
Measurements and Administration TR-TSY-000541 Beilcore Piscataway NJ July 1987
Message Detail Recording MDR FSD 02-02 -1110 GR-610-CORE Beilcore Piscataway NJ October 1993
No Service Evaluation System Interface FSD 45-13-0200 TR-TSY-000742 Beilcore
Piscataway NJ March 1990
Transport Systems Generic Requirements TSGR Common Requirements TR-NWT 000499 Belicore Piscataway NJ December 1993
5-19 BOC Notes on the LEC Networks 1994 SR-TSV002275 issue 1994 Billing Customer Data end Control AprIl
5-20
SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue Apr11 1994 Contents
Section
Signaling Contents
Signaling 61
6.1 Introduction 61
6.2 Access Line Signaling 62
6.2.1 LoopStart Signaling ....._ ....._...__ 63
6.2.2 3roundStart Signali.ng...... -.._...... 613 6.2.2.1 Call States With Ground-Start __ 6-13 6.2.3 open Switching Intervals ...... 616 6.2.4 Maintenance Tests During Idle.. .._ 6-17 6.2.5 Tests Made in the Process of Connecting or Disconnecting
Ca11 ...... _...... _...... _...._ 618
6.2.5.1 Power Cross Test...... 6-18 6.2.5.2 Low Line Resistance Test __... 6-20 6.2.5.3 Restore and Verify Test-...... 6-20
6.2.5.4 Ca11 Sequences ...... fl 621
6.2.6 Start-Dial Signal in Ground-Start...... m 6-21
6.2.7 Recognition of New Call 6-24
6.2.8 Prevention of Unauthorized Calls 6-25
6.2.8.1 Restricted Station...... 625
6.2.8.2 Toll-Diversion Signal ....._...... 6-25
6.2.9 Test PBX Loop ...... 626
6.2.10 Direct Inward lial.ing ...... _...... __...... ____ 626
6.2.11 Coin Collect and Coin Return ...... 628 6.2.12 Abandoned Call Line Snooper Feature 6-29 6.2.13 Showering...... m...... n...... n... 629
6.3 Interoffice Signaling ...... ___...... __._...._ 630
6.4 On and offHook Signals...... 633 6.4.1 Connect Seizure ....._...... _ 635
6.4.2 Answer Off-Hook...... _...... 6-35
6.4.2.1 Charge Delay ...... _ 635
6.4.2.2 Answer Signals on Calls to Directory
Ass stance ...... _...... _ 636
6.4.2.3 Cross-Office Transfer Time for Answer
Signals ...... _...... 636
6.4.3 Control of Disconnect 6-36 ...... _ 6.4.3.1 Calling-Customer Control of Disconnect 6-36
6.4.3.2 Calling-Customer Control of Disconnect with Forced Disconnect ...... e.m 638
6.4.3.3 Operator Control of Disconnect ...... 6-39
6.4.4 Guard Time ...... _....._...... _. .... 639
6.4.5 IniniediateDial ...... 643 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Contents Issue April 1994
6.4.6 Signaling Integrity 6-43
6.4.7 Reverse Make-Busy Off-Hook Make-Busy.. 6-44 6-44 6.5 Controlled utpulsing ......
6.5.1 Delay-Dial Without Signaling Integrity Check 66
6.5.2 Delay-Dial with Integrity Check 6-49 6-51 6.5.3 Generation of Delay-Dial Signals......
6.5.4 Win1t..trt 6-52
6.5.6 Glare .._...... 6-54
6.5.6.1 Glare Resolution in Electronic Switching
cffices ...... _ ...... 6-55
6.5.6.2 Trunk Hunting Method to Minimize
Glare ...... 6-56
6.5.7 StartDial Start1ulsing ...... 6-57
6.5.8 Unexpected Stop ...... r.. 6-57 rnntrrl 6.5.9 Dynamic Overload 6-59
6.6 Dial Piikino 6-59
6.6.1 Jia1Iilse Cieneration. 6-60
6.6.2 Loop and leak 6-62
6.6.3 Linuts 6-63 IialPulsing ......
6.6.3.1 Pulse Waveform Criteria 6-64
6.6.3.2 Maximum Number of Dial-Pulse Repetitions
Without Pulse Correction .. 6-65 6.6.3.3 Pulse Links and Convert 6-69
6.6.3.4 Maximum Number of Dial-Pulse Repetitions with
1u.1se Correction ...... 6-69
6.6.4 Interdigital Time ...... 6-69 6-70 6.7 1..oop Signaling ...... _...... _.. 6-70 6.7.1 ReverseBattery Signaling ...... 6.7.2 Battery-and-Ground Signaling 6-73
6.7.3 Idle Circuit Terminations and Trunk Capacitance 6-74
6.8 E.f Signaling ...... nm...... m...... n.m...... 6-74
6.8.1 Type Interface 6-75
6.8.2 Type II Interface...... 6-76 6.8.3 Type ifi Interface...... 6-77 6.8.4 Type IV 6-77 6.8.5 Type Interface...... 6-79
6.8.6 Signaling State Summary 6-80 6.8.7 Switching Methods...... 6-80
6.8.7.1 Relay Contacts...... 6-80
6.8.7.2 c..ii 6-80
6.8.8 Transient Suppression 6-82
6.8.8.1 TypelandfflMLeads...... 6-82
6.8.8.2 All Leads...... 6-83
6.8.8.3 Type II IV and Leads 6-83 6.8.9 EM Lead Current Limits 6-83
II SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Contents
6.8.10 L.izniters Current ...... n...... m...... 684 6.8.10.1 Type lvi L.ead ...... m 684
6.8.10.2 Type II SB I.1ead ...... t.s...... 684
6.8.10.3 Type III SB L.ead 685
6.8.1 Coxipatibi1ity...... nn 685 6.8.12 Interface Conversion...... _ 6-86 6.8.13 Back-to-Back Connections 6-86 6.8.14 60-Hz Inununity Requirements 6-88 6.8.15 SVorking Range 6-88 6.8.16 L.ea.l Designations eeteee...... nfl.fl 689
6.8.17 Relative Merits ...... 6-89
6.8.17.1 Interface Fype .... 689
6.8.17.2 lype Interface ... 689 6.8.17.3 Type III Interface ...... m 6-89
6.8.17.4 Fype IV Interface...... 690
6.8 17.5 Type Interface ...... 690
6.8.18 EM Lead Connection to Testboards _...._ 6-90
6.8.19 List of Service rrunks ...... fl 690
6.9 Duplex Signaling System 6-92 6.10 EM Signaling for Customer Installation Equipment 6-93
6.10.1 Protocol Differences Between Customer Installation Signaling and Central office Signaling ...... fl 693
6.10.2 EM Lead Interfaces at the POT...... 6-94 6.10.3 EM Signaling Standards for Customer Installation
...... 6-94 6.11 AC and 6-94 Supervisory Addressing Systems __ ...... 6.11.1 SingleFrequency Signaling ...... 697
6.11.2 Eciuipnient Signaling ...... _..... 698
6.11.2.1 Single-Frequency Transmiuer...... 6-101
6.11.2.2 Single-Frequency Receiver...... 6-102 6.11.2.3 Voice Path Cuts and 2600-Hz Band Elimination
Filter Insertion ...... _...... _...... _..._...____.... 6-104
6.1 1.2.4 Signaling lelay ...... m._...... n .. 6-105 6.11.2.5 Continuous Tones ...... _...... 6-106 6.11.2.6 Line Foreign Exchange Signaling ...... 6-106 6.11.3 Out-of-Band Signaling Digital Carrier and Digital
Ssvitching Systems...... 6-108 6.12 Iviultifrequency Pulsing ...... m...... m...... flee 6-112
6.12.1 the Tones Sent by Calling Station after Dialing...... 6-114
6.12.2 Multifrequency Transinitter...... 6-114
6.12.2.1 Iigit 1uration...... 6-114
6.12.2.2 ici 1uration ...... n...... n...... 6-115
6.12.2.3 Transmitter Tone Level Frequency and Timing
Lirnits...... 6-115
6.12.2.4 Transmitter Impedance 6-116
Ill BOC Notes on the LEC Networks 1994 SR-TSV..002275
Contents Issue AprIl 1994
6.12.2.5 Tests of Multifrequency Transmitters 6-116
6.12.3 Multifrequency Receiver ...... _. 61 16 6.12.3.1 Receiver Limits ...... 61 16
6.12.3.2 Ivfaxiinum Impairment...... __ 6119
6.13 Dual-Tone Multifrequency Signaling...... 6-119 6.13.1 DTMF Signaling Frequencies 6-120
6.13.2 DTMF Central Office Receiver Operation ...... 6-121
6.13.2.1 Input Impedance and Longitudinal Balance 6-121
6.13.2.2 Registration of DTMF Signals Without
..... 6121
6.13.2.3 Digits Registered in Presence of Gaussian
Noise ...... - ...... 6-122
6.13.3 DTMF Receiver Test Circuit Operation...... 6-126
6.13.3.1 Automatic Tests in 1/lA ESS Switching System- 6126
6.13.3.2 Low-Level TesL...... 6-127
6.13.4 DTMF Station Test Receiver Operation...... 6-127 6.13.4.1 Input Inipedance ...... __ 6-127 6.13.4.2 Band Edge Frequencies ... 6128
6.13.4.3 Effective Sensitivity _...... _ 6-128
6.13.4.4 Limiting Pulsing Speed and Pulse
luration ...... a..m.....fl .. 128
6.13.5 In-Service Receivers and Transmitters ...... 6-128 6.13.5.1 Use of Number Sign 6-128 6.13.5.2 DTMF Receiver Start Dialing Signal 6-128 6.13.5.3 DTMF Transmitters in Electronic Switching
Systenis ...... _...... _....._ 6129 6.13.6 Barners to End-to-End DTMF Signaling 6-130
6.13.6.1 Polarity Guard.... 6-130
6.13.6.2 Enabling DTMF Signaling in Single-Slot Coin Telephones...... m 6-130 6.13.6.3 Effects of Time Assignment Speech
Interpolation ...... _...... 6-130
6.13.6.4 Effect of Echo Suppressors and Dial Tone on DTMF Signaling 6-131 6.13.7 Increased Sensitivity DTMF Receiver for End-to-End
Signaling ...... _...... 6-132
6.14 Calling Nun.iber Jelivery ..n...... fl...... m...... mm 6-133 6.14.1 Customner Considerations.mm.n...... n.....n..n 6-133 6.14.2 BOC Network Considerations 6-134
6.14.3 Interface Data ...... _..... 6134 6.14.3.1 Data Parameters. 6-134
6.14.3.2 Data Protocol 6-135 6.14.3.3 Data Timing...._._...._ 6-136
Iv SR-TSV.002275 BOC Notes on the LEC Networks 1994
Issue ApilI 1994 Contents
6.15 LATA Access ...... 6136
6.15.1 Carrier Classification 6138
6.15.2 Feature Group 6139
6.15.3 Feature Group ...... _....._ ..._ 614.0
6.15.4 Feature Croup ... 6145 6.15.5 Feature Group Equal Access...... _ 6-146 6.15.5.1 Equal Access End Office...... 6-146 6.15.5.2 Operator Service Signallng 6-147 6.15.5.3 Signaling for Calls Not Requiring Special Operator
Signaling ...... _...... _ 6-150 6.15.5.4 Signaling North American Dialing Plan 6-153 6160 6.15.5.5 Routing ...... _ ...... _...... _.._ 6.15.5.6 International Carriers6-161 6.15.5.7 North American World Zone Calls ...... 6-167 6-167 6.15.5.8 Supervision ...... nn...n.fl...
6.16 Special Tandem Signaling CAMA OSPS and TOPS
Offices ...... n...... n...... n...... n...... nm 6-167
6.16.1 Signaling to CA.1vIA.m.....n...... n...... nn...... n.n.n 6-169
6.16.1.1 Types of Switching Systems used as CAMA
Offices ...... -_s...... n 6169
6.16.1.2 Called-Number Outpulsing Format in
C.AIvLA ...... 6-169
6.16.1.3 Overlap Outpulsing from CAMA.....m 6-169 6.16.1.4 CAMA Outpulsing Formats __.. 6-169 6.16.1.5 CAMA ANT Pulsing FormaL...... 6-170
6.16.1.6 CAMA Permanent Signal and Partial Dial
Thning ...... _...... 6-170 6.16.2 Time from Request for ANT to ANT Failure in
...n...m 6-170
6.16.3 CA.lfA Transfer...... _ 6-170
6.16.4 Operator Office Outpulsing Formats and Trnnlcing
Plans.. ..nmfl.fl...... _fl...... n....nfl....n...n.....fl 6-174
6.16.4.1 Outpulsing Format...... 6-174 6.16.4.2 Trunlcing Plans 6-175
6.16.5 Information 6-179 Iigits ...... _...... __... 6.17 Office Coin Control 6-180 Operator-Services Signaling ._...... 6.17.1 Inband Coin Control...... _ 6-181 6.17.1.1 Signals 6-181 6.17.1.2 Ringback Protocol 6-181
6.17.2 I4ultivinlc Control 6-182 Coin ...... _
6.17.2.1 Signals ...... _ 6-182
6.17.2.2 Ringback Protocol ...... _...... _...... _ 6-183
6.17.3 EIS Coin Control ..m...... 6-183
6.17.3.1 Signals ...... 6-183
6.17.3.2 R.ingback Protocol .. 6184 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Content Issue AprIl 1994
Coin 6.18 Operator-Services Office Signaling Sequences for Automatic Toll Card Service...... Service and alling ...... 6184
6.18.1 Coin Telephone DTMF Pad and Coin Totalizer Control 6.184
6.18.1.1 CoinFirst...... m 6184
6.18.1.2 DialToneFirst .. ..._ 6-185
6.18.2 Interface Prior to Calling Card Service _.._..._ 6-185
6.18.2.1 Coin-First Operator-Services System Interface prior
to Calling Card Service Introduction 6-185
6.18.2.2 Dial-Tone-First Operator-Services System Interface 6-186 prior to Calling Card Service Introduction 6.18.3 ACTS and Operator-Services System Interface_...... _ 6-186
6.18.4 Calling Card Service Operator-Services System
Interface ...... fl. ._...... fl...fl 6-188
6.18.4.1 Dial-Tone-First 6-188
6.18.4.2 CoinFirst...... m....__....._ 6194
6.18.4.3 Combined Dial-Tone-First and Coin-First. 6-197
6.19 Operator-Services Miscellaneous Services ...... 6-203
6.19.1 Combined Coin and Non-coin Operator-Services Switch
Interface ...... p..mp...... _ 6203 6.19.2 Selective Class of Call Screening Code Assignments in 6204 OperatorServices Offices ...... _...... 6.19.3 Charge-a-Call Public Telephone Service _.... 6-205
6.19.3.1 Charge-a-Call Service Dialing Restrictions 6-205
6.19.3.2 Charge-a-Call Trunking Arrangements..... 6-206
6.19.4 Postpay Coin ...... 62C6
6.19.4.1 Trunking Altematives ...fl..fl..m 6206
6.19.4.2 Restiictions ...... n...... fl 6207
6.19.4.3 Signaling ...... n 6207
6.19.4.4 Providing Ringback. 6-208
6.19.4.5 Trunking Plans and Pulsing Formats...... 6-208
6.20 Signaling to Automatic Intercept System...... _...... 6-209
6.20.1 Interoffice Signaling with ANI...... 6-210 6.20.2 Interoffice Signaling with ONI or Operator Assistance 6-210
6.21 arrier A..lariu Group ...... 6210
6.21.1 Call Processing Between Carrier Failure and Trunk
Contiog ...... __...... _....._...... _ 6211
6.21.2 Trunk Conditioning ...... _ 621
6.21.3 Carrier Restoral...... 6213
6.22 Call Progress Tones Audible Tone Signals ....rn 6-214 6.22.1 Precise Tone Plan ._...... 6-214
6.22.2 Precise and Nonprecise Call Progress Tones 6-214 6.22.2.1 Dial Tone 6214
6.22.2.2 High Low and Class-of-Service Tones...... 6-215
vi SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Contents
Ust of Figures
Figure 6-1 Principle of Operation of Loop-Start Signaling...---...... 6-4
CircuiL...... Figure 6-2 Loop Voltage Versus Current 5ESS Line ..... 6-5
Figure 6-3 5ESS GDX Line Unit Battery Feed and Supervision...... m...... 6-6
Figure 6-4 DMS-100 Switching System Loop-Start Line Battery Feed and
Supervision ...n.....n...... fl...... n...m.... 68
Figure 6-5 DMS-100 Switching System Loop- and Ground-Start Line
6-8 Battery Feed and Supervision ......
Figure 6-6 EWSD Switching System Single-Party Line Circuit...... 6-9
Figure 6-7 NEAX-61E Line Card Eight Loop-Start Lines 6-10
Figure 6-8 Loop-Start Operation on PBX Trunk Rockwell...... 6-12
Figure 6-9 Principle of Operation of Ground-Start Signaling 6-14
Figure 6-10 Ground-Start Operation on PBX Trunk 6-16
Figure 6-11 Loop Reverse-Battery Signaling for DID...... _ 6-28
Figure 6-12 Coin Collect and Return Circuit ...._... 6-29
Figure 6-13 Conlrolled-Outpulsing Formats for 1/lA ESS System 6-51
Figure 614 lialPulse Signaling ...... n...... n...... m....fl 661
Figure 6-15 Leaks for Dial-Pulse Testing _...... 6-62
Figure 6-16 Test Circuit for Dial-Pulse Templates 6-66
Figure 6-17 Dial-Pulse Template for Noninductive Test 6-66
Figure 6-18 Inductor for Inductive Dial-Pulse Test Circuit 6-67
Figure 6-19 Dial-Pulse Template for Inductive Test...... 6-68
Figure 6-20 Reverse-Battery Signaling 6-72
Figure 6-21 Battery-and-Ground Pulsing Loop Supervision 6-73
622 Lead Control Status Figure EM ...... _._ 675
Figure 623 Type Interface 676
Interface Figure 624 Type ...... 677
Figure 625 Type III Interface ...... _ 678
626 I\ Interface Fie Type ...... _...... _ 678
Interface Figure 627 Type ...... n...... flfl...... fl 679
Ix BOC Notes on the LEC Networks 1994 SR-TSV-002275
Contents Issue April 1994
Figure 6-28 Type rn-to-Type Conversion Normal Range ..._ 6-85 Fi629 Fype UtoType Conversion 687
Figure 6-30 Trunk Circuit to Trunk Circuit via Auxiliary Trunk Link 687 Repeater ....._..._.n_m.... _...... _ ...... nn.n...... n
6-88 Figure 6-31 Trunk Circuits Back-to-Back Type II......
Circuit 692 Fi632 DX Signaling ...... n...... _s......
Figure 6-33 Type Interface Customer Originates on the 6-95
6-95 Figure 6-34 Type Interface Customer Originates on the Lead ......
Figure 6-35 Type II Interface Customer Originates on the Lead...... 6-96
the Lead...... 6-97 Figure 6-36 Type II Interface Customer Originates on ......
Figure 6-37 EM 4-Wire 2600-Hz SF Signaling System _._ 6-102
6-123 Figure 638 DTS4F Digit Source
Gaussian Noise Source 6-123 Fi639 ...... _......
Figure 6-40 Gaussian Noise Test of DTMF Receiver.....m...... _ 6424
Figure 641 Inipulse Noise Source ...... fln.... 6124
Figure 6-42 Impulse Noise Test DTMF 6-125
Figure 6-43 Calling Number Delivery Message Format...... 6-135
Figure 6-44 Originating Signaling Sequence Without ANT Direct
Connection FOB ...... nnn...... n...... 6-141
Figure 6-45 Originating Signaling Sequence With ANT Direct Connection
FGB...... _...... 6-142
Figure 6-46 Originating Signaling Sequence EO Tandem Connection
GB ...... m...n...... n...... _ .. 6-143
Figure 6-47 Terminating Signaling Sequence Tandem FGB...... 6-144
Figure 6-48 Originating Signaling Sequence Operator Services InterLATA or
Intral.46STA FGD ..n...... n...... n...n...... n 6-148
Iirect Connection 6-151 Figure 649 IC/INC FGD ......
Connection 6-151 Figure 650 Tandem IC/INC FOD ......
Figure 6-51 Combined Direct and Tandem ICIINC Connection 6-152 GD ...... n....n...... n...... n...... m...... n... a.
Figure 6-52 Originating Signaling Sequence Direct Connection
GD ...... nn...... n...... 6154 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue ApdI 1994 Contents
Figure 6-53 Originating Signaling Sequence Via Access Tandem
FOD ...... n...... flfln ...... 6155
Figure 6-54 Terminating Sequence Access Through an Access Tandem FGD 6156
Figure 6-55 Terminating Sequence Direct From IC to EAEO 6-157 FGD ....._...... -..__.._ ......
Figure 6-56 INC Interconnection Indirect Originating LATA
FGD ...... 6-162
Figure 6-57 INC Interconnection Indirect Terminating LATA
FGD ...... n...u_..a.. .- ...... 6-162
Figure 6-58 International Call Originating Signaling Sequence at Direct
Connection to INC or via IC FGD...... 6-165
Figure 6-59 International Call Originating Signaling Sequence at Connection
to INC or via IC FGD...... 6-167
6-181 Figure 660 originating Signaling Sequence ...... Figure 6-61 Coin Deposit Signals ...... _ 6-188 Figure 6-62 ROH Tone Circuit Analog System 6-225
Figure 6-63 ifiustrative Digital 102 Test Trunk and Tone Generator 6-227
Figure 6-64 Reorder Condition 6-230
Fie 665 NoCircuit Condition ...... 6-231
Figure 6-66 Typical SS7 Network Structure .__ 6-258 6-260 Figure 6-67 SS7 Protocol Architecture ......
Figure 6-68 Basic Message Structure ...... rn...... 6-270
Figure 669 Procedure for Message Processing ...... n...... 6-271
Figure 670 ISIJE Message Format 6280
Information Element Format...... 6-281 Figure 6-71 ISUP ......
Figure 6-72 Detailed TCAP Message Structure with an Invoke
Comnent ...... fln..n...... flfl ...... 6283
xl SOC Notes on the LEC Networks 1994 SR-TSV-002275
Contents Issue April 1994
Ust of Tables
Table 6-1 Battery Supply5ESS Switching System _____ 6-6
6-7 Table 6-2 Battery Connections in Call Processing 5ESS System......
Table 6-3 5ESS Switching System Originating____ Call Sequence Loop-
Start ...... 6-19
Table 6-4 5ESS Switching System Originating Call Sequence Ground- Start 6-22
Table 6-5 5ESS Switching System Terminating Call Sequence 6-23
6-31 Table 6-6 Signals Required in Dialing Through the Network
Network...... 6-34 Table 6-7 Signals Used in Dialing Through the ......
6-37 Table 6-8 lisconnect Iiining ...... ___
Table 6-9 Actual Guard Time for Various Switching Systems...... 6-44
Table 6-10 Time to Restore Trunk Circuit to Idle after Disconnect ...... 6-41
Table 6-11 ffHook MakeBusy Provisions...... ____ 6-45
Table 6-12 Available Controlled-Outpulsing Methods.._...... 6-47
Table 6-13 Delay from Connect to Delay-Dial ____ 6-54
6-80 Table 6-14 Signal States Sent...... ____ ...._...... _..
Table 6-15 Service Trunks ...... fl..... _____ ...... 6-91
Table 6-16 on and offHook Conditions 6-98
Table 6-17 Typical Single-Frequency Signaling Characteristics...... 6-99
Table 6-18 Transniission Characteristics ...... _..... 6-103
Table 6-106 6-19 Typical Single-Frequency Signaling Delays......
Table 6-20 ABCD Codes Locally Switched Circuits IDT to RDT...... _ 6-111
Table 6-21 ABCD Codes Locally Switched Circuits RDT to IDT.. 6-112
Table 6-22 Multi.frecuency Codes...... flfl 6-113
Table 6-23 1VIF Sender Pulse and Interdigital Intervals...... 6-115
Table 6-24 Pvlininiuni Digit Tuning...._____ 6-118
Table 6-25 DTMF Frequency Pairs___ 6-121
Table 6-26 Feature 3roup Comparison ...... m...... 6-137
Table 6-27 of Feature 3roups ...... 6-138
xli SR.TSV-002275 BOC Notes on the LEC Networks 1994
Issue Apr11 1994 Contents
Table 6-28 Feature Group Pulsing Format from End Office to Operator
Service InterLATA and IntraLATA Calls .. 6-148
Table 6-29 FGD Pulsing Format from End Office to Operator Service
System-International Calls and Test Calls..... 6-150
Table 6-30 FGD Controlled-Outpulsing Default Timing...... 6-157
Table 6-31 Supervisory Signal Exchange Between Operator Providing ONI
and CANIA ...... _...... 6172
Table 6-32 Pulsing Format from Non-conforming End Office to an OSPS or
TOPS Office with ANT Supercombined Coin and Non-coin Trunk
Croup..._...... 6-176
Table 6-33 Pulsing Format Non-conforming End Office to OSPS or TOPS Office with ANT Combined Coin or Combined Non-coin Trunk
Group...... 6-177
Table 6-34 Pulsing Format Non-conforming End Office to OSPS or TOPS
Office with ANT ...... _...... _...... 6-178
Table 6-35 Pulsing Format Non-conforming End Office to an OSPS or
TOPS Office without 1UT ...... _...... 6-179
Table Inuorniation 636 Digit ...... _...... _...... 6-180
Table 6-37 Multiwiiik Signals and their Funcfions...... 6-182
Table 6-38 Intercept-Class Signals Transmitted to Automatic Intercept
Center ...... 6209
Table 639 Call Progress Tones...... m...... n...... n...... 6-217
Table 6-40 Glossary of Call Progress Tones 6-219
Table 6-41 Encoding Scheme for Special Information Tones 6-231
Table 6-42 Frequencies for Use in SiTs 6-232
Table 6-43 Tolerances for Announcement Machines..m...... 6-233
Table 6-44 for Treatment Applied Incompleted Call Attempts ...... 6-236
Table 6-45 Typical Global Title Translations ...... 6-277
xlii BOC Notes on the LEC Networks 1994 SR-TSV.002275 Contents Issue April 1994
xlv SR-TSV-002275 SOC Notes on the LEC Networks 1994
Issue April 1994 Signaling
Signaling
6.1 Introduction
This section covers signaling on lines and trunks within Local Access and Transport Area
LATA networks including signaling on some special-service circuits
As stated in the Foreword Notes presents snapshot view of switched intraLATA
networks as of 1993 In 1993 most of the installed switched network elements are from
ATT or Northern Telecom However equipment manufactured by Ericsson NEC
America Alcatel Rockwell and Siemens Stromberg-Carlson can be found in one or more intraLATA networks
To explain existing network-signaling characteristics and illustrate network
configurations it is necessary to refer to these manufacturers equipment These references do not constitute recommendation of these products or their manufacturers
by the Local Exchange Carriers LECs or Beilcore Moreover the illustrative use of
specific manufacturers products does not imply that similarly equipped products of other manufacturers cannot be used in intraLATA networks
There are variances among the characteristics of different manufacturers switching
systems The variances depicted in many of the tables in this section show the
operational bounds of existing systems in the intraLATA networks FR-NWT-000064
LATA Switching Systems Generic Requirements LSSGR1 presents Beilcores view of
the proposed generic requirements of new LATA switching systems for analysis
While the LSSGR addresses generic requirements for switching systems Notes gives
how it works approach It contains considerable information from the LSSGR and
standards intended as examples of how the various switching systems meet or do not meet the requirements at the time of publication not as another source of standards The
LSSGR is published more frequently than Notes The material in Notes will be out of date the first time any module of the LSSGR is republished
With circuit-associated signaling the signals are carried on the same facility as the voice path This is in contrast to Common Channel Signaling CCS where the signaling and voice carried facilities path are on separate Circuit-associated signaling on physical facilities metallic conductors transmit the uses to signals Circuit-associated signaling on carrier facilities inband out-of-band uses or signaling systems Inband signaling shares the channel with voice Single-frequency Dual-Tone Multifrequency DTMF and multifrequency signaling are all examples of inband signaling Out-of-band signaling shares the voice channel on the carrier system but without invading its analog frequency spectrum Digital carrier is good example of out-of-band or more properly out-of- slot signaling In this case most of the bits in the bit stream are reserved for voice transmission while others are shared for signaling
Access lines connect customer premises terminal equipment to switching system
The access lines can use physical or carrier facilities Trunks connect one switching
system to another Trunks also can use physical or carrier facilities
6-1 BOC Note on th LEC Networks 1994 SR.TSV.002275 1994 Signaling Issue April
6.2 Access Line Signaling
An access line in traditional terms prior to Integrated Services Digital Network ISDN is 2-wire or 4-wire interface between station demarcation point or network interface and switching system network across which are transmitted common-battery loop and voiceband supervision loop dial-pulse or DTMF address signaling alerting signals lines electrical energy Five classes of signals are used on access
Call progress signals These are audible tones or announcements that inform the network customer of call progress
the which initiates Supervisory signals These are means by customer request
for service holds connection or releases connection The supervisory signal is
With the also used to initiate and terminate charges for the call loop-start operation
on-hook or off-hook condition of the terminal is relayed to the network There is
network at the terminal With normally no supervision of the state on- or off-hook ground-start however supervision is maintained in both directions between the
terminal equipment and the network to avoid simultaneous seizures of the access line from both ends
associated with Control signals These are used for auxiliary functions equipment
connections to the Point of Termination POT or demarcation point Examples are
toll diversion and party identification
Address signals These provide information to the network concerning the desired
destination of the call usually the called number
alert the terminal Alerting signals These are supplied by the network to equipment
of an incoming call
An access line usually consists of tip lead and ring lead In the idle state the ring lead is to the at the In the various call usually negative with respect tip lead switching system these leads Maintenance states the switching system may interchange the voltages on activities may also interchange the voltages on these leads temporarily Therefore connection of given lead tip or ring to the positive or negative side of the battery cannot be ensured at the demarcation point
Technical requirements of the line interface are detailed in the following documents
TR-NWT-000506 Signaling Sections 6.1 6.42
TR-TSY-000222 InterLATA Dial Pulsing Requirements3 which covers interLATA
and intraLATA dial-pulsing includes single-frequency signaling requirements that
are not covered elsewhere
TA-NPL-0009l2 Compatibility Information for Telephone Exchange Service4
ANSI Ti .401-1988 Interface Between Carriers and CustomerInstallations
Analog Voicegrade Switched Access Lines Using Loop-Start and Ground-Start Signaling5
6-2 SR.TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
ANSI Ti .405-1989 Interface between Carriers and Customer Installations
Analog Voicegrade Switched Access Using Loop Reverse-Battery Signaling6
EIA.P11A 464-A-1989 Private Branch Exchange PBX Switching Equipmentfor Voiceband Application and inclusion of EJA 464-1
ANSI/EIA 470-A-1987 Telephone Instruments with Loop Signaling.8
6.2.1 Loop-Start Signaling
Loop-start is the most common signaling scheme used in the public switched network It
is used to provide the following 2-way services
Message Telecommunications Service MTS for residence and business
Public Telephone Service PTS
Manual or automatic data or facsimile service
One-way incoming service to an attendant at Private Branch Exchange PBX or Automatic Call Distributor ACD
In the loop-start mode of operation in the idle or on-hook state of the terminal the network connects the tip conductor to the positive end and the ring conductor to the negative end of voltage supply The positive end may or may not be grounded For the line in example 5ESS switching system uses floating supply some portion of the call whereas most other switches employ grounded supply Digital Loop Carrier DLC systems between the switch and the demarcation point may also use either floating or grounded battery supply
Figure 6-i shows the principle of operation of loop-start signaling The most common voltage on the line is 48 However other line conditions can cause the line voltage to be 105 and low The as high as as as high voltages are generally from range- extension equipment although the line circuit for the 5ESS switching system can also provide voltages over 50 The nominal dc supply voltage for DMS10 and DMS i00F switching systems is 50 dc
is trademark 5ESS registered of ATT
DMS is registered trademark of Northern Telecom Inc
DMS-100F is trademark of Northern Telecom
64 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling Issue April 1994
Demarcation
Point Local Switching System Terminal Or Carnler System Switchhooic
ground is omitted with floating battety teed
Figure 6-1 Principle of Operation of Loop-Start Signaling
Figure 6-2 shows voltage versus current for the 5ESS line circuit It refers to voltage
measured at the main distributing frame under conditions of high battery voltage
52.5 and shows the action of the current regulator Figure 6-3 shows the
corresponding line unit The system has line current supply in the talking condition
anticorrosion circuit that will sink to to the with an up 15 mA hold tip Oto with
respect to ground
Tables 6-1 and 6-2 show which portion of the 5ESS switching system line unit is
supplying battery at the various stages of the call Figure 6-3 shows 5ESS switching system Gated Diode Crosspoint GDX line-unit battery feed and supervision arrangement The GDX concentrator contains the line concentrator the line scanner and
the battery supply for the line scanner The .4-kfl resistor in this circuit is the ground
applied during the fIrst 250 ms of dial tone on ground-start call See Power Cross
Test Section 6.2.5 The battery for the GDX concentrator is grounded supply The
High-Level Service Circuit HLSC also uses grounded battery for ringing and testing
The channel circuit supplies floating battery for talking dialing supervision and testing
6-4 SR-TSV-002275 SOC Notes on the LEC Networks 1994 issue ApdI 1994 Signaling
80
60
40
20
10 20 30 40 50
Loop Current mA
Figure 6-2 Loop Voltage Versus Current 5ESS Line Circuit
Figures 6-4 and 6-5 show DMS100 10-line circuit cards Figure 6-4 shows line card for loop-start line The line card illustrated in Figure 6-5 is for combination ioop- or ground-start line that may be used for coin or other special applications note option switch Another line card with 48 ioop- or ground-start adds 48 relay to the circuit of Figure 6-5 When operated it transfers the ring battery feed from48 to
shifts the to ground and tip battery feed from ground 48 Analog-to-digital A/D and digital-to-analog D/A conversion are contained in the line circuit chip The circuit loss is software-adjustable
Figure 6-6 shows simplified schematic diagram of the analog line circuit for single- party lines that is part of the Siemens EWSD switching system Other line circuit designs are available for such special functions as 2-party coin or ground-start lines
These have battery-feed arrangements similar to that of the single-party line circuit
DMS-100 is registered trademark of Northern Telecom Inc
EWSD is registered trademark of Siemens AG
6-5 SOC Notes on the LEC Networks 1994 SR-TSV002275 1994 Signaling issue AprIl
GDX Concentrator GDX Access Channel Circuit
TWO xx
._
1.4K
-48
Legend
Sensor Scanner High-Level Service Circuit BF Battery Feed CB Current Break
ACB And-Corrosion Bias
GDX Gated Diode Crosspoint ONC Concentrator
Figure 6-3 5ESS GDX Line Unit Battery Feed and Supervision
Table 6-1 Battery Supply5ESS Switching System
Scsnner knnl High-Level Service Circuit
FCG Tests Idle Line Dialing
Power Cross Tests PBX Signaling Talking PX
Disconnect Per-Call Coannel Tests Permanent Signal
Line Test Line Flash Ring Pie-uip Tests
Line Test Ringing Geator
Ringing Connmiity
Party Teats
Coin Functions
Restore and Verify Test
Otannel Diagnostics
Fabric Exercise
Office-to-Office Tests
64 SR-IS V.002275 SOC Notes on th LEC Networks 1994 Issue AprIl 1994 Signaling
Table 6-2 Battery Connections in Call Processing 5ESS System
ORIGINATION SEQUENCE
Call State idle Origination Dialing Talldng Disconnecting Idle
Connected Scan HLSC Channel Channel Channel Scan Circuit Channel HLSC
Tip XPT GS 250 ms Tip XPT LS _____ Tip XPT LS ______
TERMINATION SEQUENCE
Call State Idle Termination Ring Silent Ring Disconnecting
Connected Scan HLSC HLSC Channel HLSC Channel Circuit Channel HLSC
Tip XPT GS Tip XPT LS Tip XPT LS
Gild
Tip
-48v
Scan
Anticorroslon Bias
Current Threshold Detector
FCC False Cross and Ground
GDX Gated Diode Crosspolnt
GS Ground Start
HLSC High-Level Service Circuit LS Loop-Start
Px Power Cross
Supervisory Detector xPT Croespolnt Tip crosapoint closed
TIpcrosspoIntc1osedgroundontIpduflngdlallngandtaIIdng Service Class PBX
6-7 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Signaling Issue April 1994
Test Ring Aooees Bus
co
Legend
CO Cutoff Relay
RG Ring Relay
TA Test-Access Relay
Figure 6-4 DMS-100 Switching System Loop-Start Line Battery Feed and
Supervision
Test Ring eesBu LP% Bus
TA RG I1 200 .4 yv.- -4eV Ring
RG RV TP 200 lip UN A%--
Current Detector
GD Legend
CO Cutoff Relay GD Ground-Start
LP Loop-Start
RG Ring Relay
RV Reversing Relay
TA Test-Access Relay
TP lip-Ground Relay
Figure 6-5 DMS-1 00 Switching System Loop- and Ground-Start Line Battery
Feed and Supervision
6-8 SR-TSV-002275 BOC Notes on the LEC Networks 1994 iuue2Apill 1994 Signaling
OUT IN
Teet-Acss MultIe To Mbopocessor Ri1g Relay 12V Test-Out Relay Test-tn Relay Dlsxnnect Relay
Figure 6-6 EWSD Switching System Single-Party Line Circuit
A/D and D/A conversion of speech is done by Siemens Customer Optimized
Subscriber Audio Processing COSLAC chip which is programmable for such functions as transmit level receive level time slot assignment hybrid balance etc Other chip outputs control relay drivers for such functions as ringing application test-access switching or line disconnection
As in seen Figure 6-6 the batteiy-feed resistors are connected to the subscriber line tip and ring conductors at all times except when the line is purposely disconnected from the line circuit that is the line circuit is in precuwver state or the line circuit is isolated from foreign potential present on the line This single-source battery-feed arrangement eliminates most of the Open Switching Intervals OSIs described in Section 6.2.3
Figure 6-7 shows the NEC NEAX-61E switching machine 8-circuit line card It provides
A/D and DIA conversion test access and ringing overvoltage protection padding loop balance and 2- to 4-wire conversion The 8LC is used for ordinary loop-start service while more complex 4-circuit card 4LC is used for coin ground-start or other special circuit applications The 4LC adds polarity-reversing relay 130 coin-control feed the on tip lead relay feeding 48 on the tip in place of ground and simultaneously charging the feed to the ring from 48 to ground and 48 and -48 ground detectors
Low voltages on the line at the demarcation point under no-load conditions can be caused by devices inserted in the line to isolate the customers equipment during the idle period
6-9 BOC Notes on the LEC Networks 1994 SR-TSV002275 Issue 1994 Signaling AprIl
These devices are known as Maintenance Terminating Units MTUs The isolation connection the terminal permits testing the loop without physically removing the to
The terminal appears as very high resistance to the network during on-hook hence an off-hook open-circuit condition exists To initiate call the terminal sends an signal by and dc current from closing the loop lowering the tip-to-ring dc resistance drawing the network The network detects the current as seizure signal This process of dc monitoring the terminal status by the network is called loop supervision The request
of the network is for service initiated at the calling end is termed seizure The response in the the application of dial-tone signal superimposed on the dc loop current flowing failure of circuit Dial tone is discussed with other call progress signals below During 18 primary ac at the serving switching system the current may drop to mA
Ti Super- Hybrid FrornrFo
vision 2w-4w Digital and Conver- CODEC Une
Battery slon Switch Feed 4W Ring ______1-1- ___ 0- Ti
Selectable
Balancing
RIngTrtp Netwoilc CO CO T2 Detector
ii CRCRG
ToNext
Circuit
co ctdoe CR CotInuous RWglng CRG Coiiuous RigI1g Grosid
______RRgrg ____ TI Ta.i-ss Test Access Teet4ccees
Figure 6-7 NEAX-61 Line Card Eight Loop-Start Lines
See ANSI T1.401-19885 or EIAITIAJ464-A-19897 for exact current/voltage characteristic of
terminal The highest dc resistance that will meet the requirements of ANSI T1.401-1988 or
EIAFLA/464-A-1989 for an off-hook is 330 with 20 mA flowing
6-10 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SignalIng
the call will send the address of the After receiving dial tone the terminal originating short of called party by either DTMP or rotary-dial signaling description rotary-dial 6.13 characteristics is provided in Section 6.6 DTMF is covered in Section
from the of dial tone Most switching systems in the network monitor the time beginning until the detection of the first address information character If no address character is received in to 40 seconds the loop may be connected first to an announcement then to Receiver Off-Hook ROll tone and then to an open-circuit condition for up to
1.2 seconds Some switching systems like EWSD open the loop for 800 ms before connecting the line to recorded announcement ROH tone is applied after the
is announcement The second procedure is specified in the LSSGR If an on-hook signal
terminal and if the terminal remains on-hook it will received at any time from the eventually be restored to normal idle state
lines in The network provides no standard release signal on loop-start Even switching of systems that interrupt loop current as part permanent signal treatment range-extension terminal for equipment may block this signal from reaching the terminal Therefore current in loop-start service should not be designed to depend on loop interrupts disconnect permanent signal treatment as primary signals
call After sending the called-address information the calling party may hear progress tones as the call completes to the called terminal Audible ringing would indicate
successful connection while tones or announcements would indicate other conditions Section 6.22 Call-progress signals are discussed in
The called terminal is alerted by ringing signal which is nominally 88-V 20-Hz in the superimposed on 48-V nominal dc voltage There are other forms of ringing used 15 70 telephone industry In these the ringing frequency can vary from approximately to The Hz with the ac ringing voltage and the dc supervisory voltage varying widely either The can be ringing and superimposed dc voltage can appear on tip or ring ringing
tip-to-ring tip-to-ground or ring-to-ground
is in two Selective ringing ringing only one party on multi-party line accomplished from to ways The first method is to change the superimposed voltage positive negative
By ringing on the tip or the ring and using positive or negative superimposed voltage
four selective ringing codes can be obtained This method is used by the independent
LECs and is the predominant method used by Bell Operating Company BOC
intraLATA networks The second method is to use several ringing frequencies
Ringing-to-ground can be used Since 60 Hz is frequency in one of the ringing systems
this type of ringing is usually applied tip-to-ring in balanced fashion to prevent false few BOCs operation of the 60-Hz ringer Frequency-selective ringing is used in only but in many independent LECs
See ANSI T1.401-19885 or EIAFIA/464-A-19897 for DTMF and rotary-dial signaling requirements
6-11 SOC Notes on the LEC Networks 1994 SR-TSV-002275
Signaling Issue April 1994
With superimposed-voltage ringing the ringing signal is applied between tip and ring for
most 1-party lines Usually the ringing and superimposed dc voltage are on the ring
the is selective 2- semi-selective while tip grounded However or 4-party and 4-party or
8-party lines have ringing on either tip- or ring-to-ground
The ringing signal generally consists of ringing interval followed by silent period
central office line be seized for The typical silent interval is seconds As result can
as long as seconds before seizure can be recognized at the station The person at the
station may attempt to originate call during this interval This is not normally
problem since the person originating the call from the station end is usually the person to
whom the call is being directed However ground-start would give dc signal as soon as
the line was seized This is an important difference between loop-start and ground-start
called the the The party answers ringing signal by going off-hook This trips removes
ringing signal and cuts-through the talking path The tripping interval is typically
200 ms although ringing can continue for longer periods before being tripped
call is ended by the calling or called terminal or both going on-hook This action is
called disconnect it brings the terminal to the idle state when little or no dc loop current
flows in the circuit There is no signal sent from the network to either the called or the
calling terminal at disconnect The various methods of control of disconnect are covered
in Section 6.4.3
An example of the terminal end when using loop-start signaling is shown in Figure 6-8
This is the arrangement for central office PBX trunk central office line in Rockwell
Galaxy system
Central Office Galaxy 2WCO
Open End aosed End
Cirft Loop
Ring GEN
sav Ring Detector
Figure 6-8 Loop-Start Operation on PBX Trunk Rockwell
6-12 SR-TSV.002275 BOC Nots on the LEC Networka 1994
Issue April 1994 SIgnaling
6.2.2 Ground-Start Signaling
Ground-start signaling for 2-way dial facilities was introduced in the early 1920s Its
purpose is to reduce the likelihood of seizure of the facility by both ends of the circuit
during the silent interval between rings
Ground-start is used central office trunks with Direct signaling typically on 2-way PBX Outward Dialing DOD and attendant-handled incoming-call service In addition
ground-start signaling is typically used on ACD service and for automatically originated data service
The ground-start line conductors transmit common battery-loop supervision DTMF
address signaling or loop dial pulses alerting signals and voiceband electrical energy
Ground-start lines are often used rather than loop-start for the following reasons
They provide signal that can act as start-dial signal It is not necessary to detect dial tone in most situations See Section 6.2.6
They provide positive indication of new call
They help prevent unauthorized calls
They provide indication to calling or called party of distant-end disconnect under normal operation
6.2.2.1 Call States With Ground-Start
To describe the call states in ground-start it is necessary to assume the actions that terminal can take These are not the only actions terminal can take and still be compatible with the network
In the idle state the network applies negative dc voltage to the ring conductor and keeps the tip conductor floating As shown in Figure 6-9 an office with conventional battery would permanently ground the battery An office with floating battery would temporarily ground the positive side of the battery supply
6-13 BOC Not. on th LEC Networks 1994 SR-IS V.002275 Signaling Issue AprIl 1994
Demarcation Local Switching System Point TOflTllfl Or Carrfler System
Is used with floating battery feed It Is closed In the Idle and seMce-request states With conventional feed the battery Is permanently grounded
Value of resistance depends on switching system
Figure 6-9 Principle of Operation of Ground-Start Signaling
In the idle state the terminal presents an open circuit tip-to-ring and ring-to-ground The
terminal has detector connected tip-to-battery to detect seizure off-hook from the
network typical detector has resistance of 10000 to 20000
To initiate call the terminal grounds the ring side of the line by operating contact
The resultant current in the ring conductor is detected by the network In turn the
network the side of the the side and in applies positive battery to tip switching systems
with floating battery removes ground from the battery supply
The result is that in the is switching systems with conventional battery tip grounded In with switching systems floating battery there is voltage between tip and ring with
ring the more negative until the line becomes idle again The terminal will detect the
ground on the tip or voltage between tip and ring when the switchhook contacts are closed and contact is open This places the terminal in the loop mode
The terminal in stays the loop mode for addressing call processing and communication
states The line reverts to the ground-start mode only after the terminal or network goes on-hook All actions of the network and terminal already covered for loop-start line apply when ground-start line is in the loop mode
6-14 SR-TSV.002275 BOC Not. on th LEC Networks 1994
Issue April 1994 SignalIng
At disconnect four different combinations can occur The network or terminal can disconnect first and the line can have conventional battery supply or floating battery supply The possible disconnect sequences are as follows
When the network disconnects first on line with conventional battery the network
removes ground from the tip which in turn removes current from the line The
terniinal waits about 350 ins to determine that the open is disconnect and not an
OSI It then idles the line in preparation for new call Some switching systems
guard the line during the disconnect interval and some do not before returning to idle ready for new call
When the network disconnects first on line with floating battery the network
removes battery from tip and ring which in turn removes current from the line The
network waits guard time of about 600 ms minimum before returning to idle The
terminal waits about 350 ins to determine that the open is disconnect and not an
OSI It then starts line disconnect procedure The terminal may or may not have
guard time between detecting disconnect and making the line idle
When the terminal disconnects first on line with conventional battery the terminal
opens the loop The terminal holds the line busy until the ground is removed from
the tip To prevent noise on the line from prematurely idling the line the terminal
may hold the open before returning the line to idle
When the terminal disconnects first on line with floating battery the terminal opens the loop The terminal may hold the line busy for guard time The network disconnects and holds the line out of service for period of 600 ms minimum before
returning the line to idle
To initiate call to the terminal the network connects ringing circuit to the line This applies ground to tip and negative battery with 20-Hz ringing to ring Since ringing may or may not be present when the call is initiated the ground will make the line busy at the terminal Ringing is used as an alerting signal at the terminal The terminal answers the call by closing the switchhook contact Figure 6-9 The network responds by tripping the ringing signal and connecting the talking path The battery supply as before may be either conventional or floating Disconnect is identical to that described for calls originated by the terminal
An example of the terminal end when using ground-start signaling is shown in Figure 6-
10 the arrangement for 2-wire PBX tnink central office line in Rockwell Galaxy system
6-15 BOC Notes on the LEC Networks 1994 SR-TSV.002275 1994 Signaling Issue AprIl
Ring GEN
48V
Figure 6-10 Ground-Start Operation on PBX Trunk
6.2.3 Open Switching Intervals
call OSIs are generated on lines by switching systems as the call is switched from one state to another An Os removes battery and ground from the line or line voltage in
for of time OSIs on systems that have floating line voltage supply period occur Inward service loop-start and ground-start but not on Direct Dialing DID
manufactured have call The All switching systems by ATT OSIs during setup 1/lA ESS and 212B ESS systems also have OSIs on established calls when using custom-calling services The 5ESS switching system does not have OSIs when custom- and removal calling services are used For the EWSD system only the application do have tripping of ringing cause OSIs The DMS-10 and DMS-100F systems not an
OS The NEAX-61E system has no OS except as part of permanent signal and partial dial treatment Generally OSIs are less than 350 mswith more than 100 ma between OSIs
Some of the changes of call state that can cause OSIs are
Connection of calling line to dial tone
ESS is trademark of ATT
6-16 SR-IS V-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 SIgnaling
Completion of dialed digit by calling line
Completion of sending called-address information by calling line
Completion of sending called-address information by originating switching system
Change from ringing to silent interval or silent to ringing interval
Start and removal tripping of ringing
Switching call to 3-way bridge for custom-calling services or returning from the
3-way bridge to normal talking condition
Switching to call waiting tone
Transferring call
Placing call on hold
Using 3- or 6-port conference bridge
Whether OSIs are experienced or not depends on the switching system being used The line using custom-calling service will always experience the associated OSIs On an intraoffice call the other line or lines connected to the line using the custom-calling services will also experience them
6.2.4 Maintenance Tests During Idle
To maintain the network properly test signals are periodically applied to the loop at the central office These tests occur on loop-start and ground-start but not on DID service
The voltage applied to the terminal equipment in the on-hook state can be up to maximum of 202 dc between the tip and ring conductors or between either conductor and ground Maintenance testing signals of up to 45 ac rms from tip-to-ring tip-to- ground and ring-to-ground in the frequency range of to 3800 Hz may also be applied when the equipment is in the on-hook state
These network maintenance tests are as follows
ac signals of less than 10 rms or signals of 24 Hz superimposed on 70 to
70 dc on tip with ring grounded on ring with tip grounded or on both tip and
ring with respect to ground
of 10 and ac signals rms or less tip-to-ring or tip- ring-to-ground at any frequency from5tol000Hz
ground on tip orring
dc voltages from to 202 tip-to-ring or on tip with ring grounded or on ring with both and with tip grounded or on tip ring respect to ground
ac signals of rms or less tip-to-ring at any frequency from 1000 to 2000 Hz It
is desirable that the customer premises equipment not respond to ac signals of
rms or less tip-to-ring at any frequency from 1000 to 5000 Hz
6-17 BOC Notes on the LEC Networks 1994 SR-TSV002275 Issue 1994 Signaling Api11
the These conditions may be applied during testing Such tests are applied sequentially series of tests may last up to 12 seconds
6.2.5 Tests Made in the Process of Connecting or Disconnecting Call
detectable Three tests made in the process of connecting or disconnecting call cause condition outside the switching system The tests are made for the most part by the
1/lA ESS switching system Not all switching systems use similar tests Where other
mentioned The 5ESS is systems are intended they will be specifically switching system discussed separately The tests can occur on loop-start and ground-start but not on DID service
6.2.5.1 Power Cross Test
The 1/lA The power cross test is made before originating and terminating calls ESS 212B ESS and 5ESS switching systems have power cross test of the type described need for the DMS-100F systems do not have such test In the NEAX-61E system the the line circuits for power cross test is eliminated because the system continually scans from service loop trouble conditions and removes lines with detected problems
of about 25 to 50 In the 1/lA ESS switching system power cross test an OSI ms 16 precedes the test The test detects ac or positive dc voltages over as power cross
lines To make this detectors are on loop-start or ground-start test placed tip-to-ground kfl calls and ring-to-ground The input resistance of each detector is about 18 on
detector resistance is originating from the line For calls terminating to the line the ring
is about 36 kfl The test lasts about 50 to about 18 kfl while the tip detector resistance
the connected to the line 100 ms Dial tone battery on the ring and ground on tip are caused call failures calls immediately after the power cross test The test has on terminal the 18-kfl originating from ground-start lines where the recognizes input resistance of the detector as grounded tip and proceeds as if dial tone were present
in and The power cross test in the ESS switching system is the same loop-start ground- for about 10 20 start lines The test first places 632-fl resistor tip-to-ring to ms the the call This ground-start terminal has connected ground to ring to start ground side of the the side The passes through the 632-fl resistor to the tip line grounding tip with OSI of 100 150 Dial on the and test then opens the line an to ms tone battery ring connected the line after the As with the 1/lA ground on the tip are to immediately OSI ESS this test has caused call failures on originating calls from ground-start lines
and The power cross test in the 5ESS switching system differs between ground-start
is connected to both and before dial tone In loop-start In loop-start ground tip ring addition OSIs occur Since these conditions should not cause call failures they will not be discussed further In ground-start OSIs occur before dial tone but there is no connection of either battery or ground to tip or ring Dial tone floating battery and
is ground on the tip are connected to the line at the same time The ground on the tip removed about 250 ms after the start of dial tone For more details see Table 6-3
6-18 SR-TSV-002215 BOC Note on the LEC Network 1994
Issue ApIll 1994 Signaling
The EWSD system continuously monitors for ac power cross by means of the loop detector If cross is detected the line is isolated from the line circuit by the disconnect relay Automatic retesting occurs periodically at short intervals and the line is automatically restored to service if it is verified that the power cross fault has been removed
Table 6-3 5ESS Switching System Originating Call Sequence Loop-Start
CallState
lime inns 20 40 80 80 100 120 140 180 180 800 240 280 280 300
Cable Comec-
tion to Netwodc dwmel bs8ery
Call State Details
Connect HLSC GDX access close Stage access GDX crosspoint delay 10 ms
Perform FCG test delay 40 ms
Read results of first FCG test delay 10 ms
Perform No Continuity test delay 40 ms
Get results of No Continuity test close first-stage GDX crosspoints open scan crosspoints
close tip crosspoint if line is served through DLC or is PBX and class of DLC or PBX
requires ground on tip or if Coin First delay 80 ms LS channel Verify scan-crosspoint order verify scan on-hooi start PX test power-up GDX not connected to network yet delay 50 ms
6A Get PX results verify channel on-hool delay 10 ms
SB Close Stage GDX crosspoints delay 10 ms
Apply loop bridge 619 tip-to-ring delay 40 ms
Verify channel off-hoolc remove loop bridge release HLSC GDX access delay 20 ms Idle HLSC memory test phone off-hool enable supervisory scan
For abbreviations and block diagram of line circuit see Table 6-2
6-19 BOC Notes on the LEC Networks 1994 SR-TSVOO2215 issue 1994 Signaling AprIl
6.2.5.2 Low Line Resistance Test
The low line resistance test is designed to prevent false charging where irregularities exist in the called line check is performed in all switching systems for example 1/lA ESS 212B ESS 5ESS DMS-10 and DMS-100F to ensure that tip-to-ring avoid immediate of ringing The resistance is high enough to ring trip upon application call In the 1/lA ESS test is performed prior to ringing in the terminating sequence 250-fl switching system on loop-start lines the test is made by applying approximately from to the On ground to the tip and approximately 250 fi battery ring ground-start
other this test on lines lines the battery and ground are reversed In systems ground-start detail in Section is known as PBX loop test The PBX loop test is discussed in more below 6.3 kfl 6.2.9 This test in the 1/lA ESS switching system will see resistance as failure and may see resistances below 17 kfl as failure
the detector and In the EWSD system the loop detector is more sensitive than ring trip false seizure will be detected the line therefore no special ring pretrip test is required when call will end up in the permanent-signal state and therefore test busy terminating is attempted
6.2.5.3 Restore and Verify Test
5ESS The restore and verify test is made in 1/lA ESS 2/2B ESS and switching systems
is It is not made in DMS-l0 or DMS-100F systems Where performed it automatically
and before it is idled made on line after the line is involved in network connection
line and if the cutoff contact This test determines if supervision has been returned to the and has been closed The restore and verify test procedure differs between loop-start 1000- 2000-fl resistor from the ground-start lines The 1/lA ESS system places or tip and for line The to the ring for loop-start line or between ring ground ground-start the resistance of the line ferrod test takes about 50 to 100 ma With loop-start service and 660 fi being tested is approximately 660 fi to battery on the ring side of the line to the resistance of the line ferrod is ground on the tip side With ground-start service
the line The side of the line is approximately 1320 fi to battery on the ring side of tip open
the The restore and verify test is not made in the EWSD switching system because
unless the line circuit is There is no battery feed is never removed from the line faulty line circuit cutoff relay in the loop-start
6-20 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SignalIng
6.2.5.4 Call Sequences
Table 6-3 covers an illustrative call sequence of loop-start call originating in 5ESS office from customer off-hook through line testing application of dial tone and testing after dial-tone application Table 6-4 covers the call sequence of an originating ground- the of to start call through the same stages of the loop-start call plus application ground after the of dial tone Table 6-5 covers the call the tip of the line for 250 ms start sequence of terminating call on either ground-start or loop-start
6.2.6 Start-DIal Signal In Ground-Start
start-dial in without the There is no single dc signal that can act as signal ground-start dial There dc in each of the necessity of detecting tone are however signals switching systems that can perform this function The first signal is ground on the tip the oldest of the dc start-dialing signals It can be used with 5ESS with restrictions due to floating battery DMS-l0 DMS-100F and NEAX-61E switching systems The power cross test in 1/lA ESS and ESS switching systems causes ground to be connected to the tip before dial tone These systems cannot use ground on the ring as start-dial signal
They can however use second method which is dc voltage between tip and ring
6-21 BOC Note on the LEC Networks 1994 SR-TSV-002275
Signaling issu AprIl 1994
Table 6-4 5ESS Switching System Originating Call Sequence Ground-Start
66 Call State lllIlItlIllIlllIIIIllllIllIllIIIIllIl
TIme in ma 20 40 00 80 100 120 140 160 200 240 200 260 300 340 360 380
able Connec- ca rloccm Uris ban to Network
Cd State II Ill II II ill II Ill
TIme In rns 20 40 80 100 120 140 180 200 200 240
Cable Connec- up cfosspdrl com.ctsd fo PSX gnslIn tion to Netwodc 1.5k oIm dp rd di baeeiy
Call State Details
Connect HLSC GDX access close second stage access delay 10 ms
Perform FCG test delay 40 ms
Read results of FCG test delay 10 ms
Perform No Continuity test delay 40 ms
Get results of No Continuity test close first-stage GDX crosspoints open ring-scan crosspoints set HLSC start of GS power-cross PX test delay 10 ms
PX Set values for PX test and connect HLSC relay access
Verify scan-crosspoint orders verify scan on-hook activate GS PX test power-up channel
channel not connected to GDX network yet delay 50 ms
6A Begin channel discharge open first-stage GDX crosspoint disconnect HLSC GDX access
channel channel but break circuit set get PX results verify on-hook power-down keep closed HLSC delay 10 ms
6B Close Stage GDX crosspoints close HLSC GDX crosspoints delay 20 ms
6C Add 61 8-fl bridge for faster channel discharge delay 20 ms
6D Open channel-break circuit set HLSC tip voltage
6E Remove HLSC delay 40 ms
Open HLSC relays apply loop bridge delay 40 ms Remove loop-bridge order disconnect HLSC GDX access delay 20 ms
Idle HLSC memory enable supervisory scan close first-stage GDX crosspoints
Subsequent to completion of the process another process will power-up the channel connect the
tip-scan crosspoint signal the PBX to convert from ring-ground to loop supervision connect digit
receiver and apply dial tone The tip-scan crosspoint remains connected for 250 ms dunng which time the PBX is expected to convert to loop supervision The 5ESS switching system will accept
digits from the PBX 70 ms after the tip ground is applied
For abbreviations and block diagram of line circuit see Table 6-2
6-22 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 SignalIng
Table 6-5 5ESS Switching System Terminating Call Sequence
Call State II II II II
Time in ms 20 40 80 100 120 140 160 180 200 220 240 260 Cable Connec- px FCG Low Une Resistance tion to Networic No ContN LRtes40VRgrd
200Q 6A Ring
delay
Call State 10 11 12 13 14 II
400 460 480 500 lime in ms 280 300 320 340 360 380 420 440
Low Une Resistance channel tests
testconthued channel battety
Call State Details
Connect HLSC GDX access close second stage access GDX crosspoint
Perform FCG test delay 40 ms
Read results of first FCG test delay 10 ms
Perform No Continuity test delay 40 ms
Get results of No Continuity test close first-stage GDX crosspoints open scan crosspoints
served is and class of or except for tip if line is through DLC or PBX DLC PBX requires
ground on tip delay 10 ms
Verify scan crosspoint orders start PX test delay 50 ms Check PX results delay 10 ms
Start pre-trip test delay 170 ms
Check pre-trip results power-up channel not yet connected to network delay 40 ms
10 Verify channel is on-hoolc connect channel to GDX access networic delay 10 ms
11 Connect loop bridge delay 40 ms 30 12 Verify channel is off-hool open channel break circuit and power-down delay ms served 13 Remove loop bridge open channel GDX access crosspoints if GS or line is through
DLC or is PBX and class of DLC or PBX requires ground on tip open tip delay 20 ms
14 Select ringing configuration and start ringing
For abbreviations and block diagram of line circuit see Table 6-2
6-23 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Issue 1994 Signaling AprIl
be used in of In the systems previously listed dc voltage between tip and ring can place ground on the tip
In situations Dialing can begin 70 ms after the start of dial tone some ground on tip or dc both and dc between and occur nng voltage on tip ring or voltage tip ring simultaneously with dial tone as follows
Ground on tip
is the for about 250 after the start 5ESS switching system ground on tip only ms
of dial tone then is removed for the rest of the call
DMS-l0 and DMS-100F systems
EWSD system
NEAX-61E system
dc voltage between tip and ring
DMS-l0 and DMS-100F switching systems
1/lA ESS system
ESS system
dc test plus timing can be used on all systems in any intraLATA network Dialing can line begin 275 ms after voltage is applied between tip and ring on ground-start
6.2.7 Recognition of New Call
new terminating call can always be recognized on ground-start line because there is an offhook condition from the network and ringing is present on the line Not all terminal equipment detects the combination of off-hook and ringing fromthe network as the start of new call Some use only the on-hook to off-hook transition of the network
This simpler method is equally effective on lines with floating-battery supply because the network guards the line for 600 ms after disconnect This provides guaranteed on- hook interval much longer than any possible OS for the terminal to recognize However there is no guarantee of an on-hook interval on lines with conventional battery supply
and Ground on tip and battery on ring on lines with conventional battery feed and voltage between tip
ring on lines with floating battery
The 1/lA ESS switching system has 2-second guard time between calls on ground-start lines when the
system that originated the call disconnects first It does not have guard time between calls when the
terminal originates the call or when the terminal disconnects first The 22B ESS switching system has
1-second guard time on disconnect of either ground-start or loop-start lines when the line is marked with
PBX class of service
6-24 SR-TSV.002275 SOC Notes on the L.EC Networks 1994
Issue Apiil 1994 SignalIng
The line can be seized in less than 50 ms after disconnect in switching systems without guard time.t
Failure to recognize new call at the terminal causes call failure known as ring-no- attendant answer With this failure the called party hears audible ringing but the never answers the call
6.2.8 Prevention of Unauthorized Calls
Ground-start aids in preventing unauthorized calls This is described as follows
6.2.8.1 Restricted Station
restricted station may be connected to central office by the attendant The attendant may dial for the station or may allow through-dialing by the station When the station office remains off-hook after the called party disconnects the station cannot get central
if dial tone at the end of the called-party disconnect timing sequence ground-start operation is used This occurs because the central office has reverted to the ground-start mode It requires ground on the ring conductor to activate the service request sensor current detector or line ferrod whereas the station can provide only loop closure
6.2.8.2 ToIl-Diversion Signal
The toll-diversion signal is reversal of the loop voltage During the originating call setup period the battery polarity supplied to the terminal is -48 on ring and ground on tip The toll-diversion signal is 48 on tip and ground on ring Most range-extension equipment including carrier systems does not repeat the tolldiversion signal be used Consequently toll restriction that does not require central office signal must when range-extension equipment is in the facility
For toll-diversion purposes most central office switching systems can be arranged to provide momentary battery reversal 50-150 ms long to dial PBX ii prefix or area code involving toll charges is dialed This reversal is also sent if the numeral is dialed because the station could request the operator to place long-distance call
feature in the lilA ESS and DMS-lOO switching systems Uniform Call Distribution UCD helps the
recognition of new calls This feature advances the first-choice selection through the hunting group after
each terminating call For example if the last call was placed on ground-start line the next hunt for
line if idle ground-start lines will start with line continue to the end of the group and start over at the of necessary This action spreads the calls throughout the hunting group As result probability
placing new call on ground-start line just disconnected in the central office but not yet disconnected at lowest This the terminal is less than if the group were always hunted from the highest preference to the
advantage disappears when only one trunk in the group is idle or when ringing is used to recognize new
call
6-25 BOC Notss on the LEC Networks 1994 SR-TSV.002275 Issue 1994 Signaling April
6.2.9 PBX Loop Test
all network The PBX loop test is made on calls to ground-start lines by switching before the at the terminal is systems It prevents attaching new call to terminal loop network could fail If the call failed opened Without this test call connected to the would not hear an audible because the would be tripped by the calling party ring ringing for the the closed loop at the terminal In addition the calling party would be charged
This of failure is called call even though it was not completed type no-ring no-answer
the of the line detector in The following is typical test Ground is placed on ring
resistance is detected the series with battery is placed on the tip If high open loop
is released call is completed If low resistance is detected that circuit to the terminal second circuit and second circuit is selected The PBX loop test is made on the Any
is muted to reorder tone call failing the second test
The way most central offices select ground-start lines in hunting group is incompatible selects with some maintenance or traffic-control activities The central office generally
the least This means that ground-start line from the most preferred to preferred many the least more attempts will be made on the most preferred ground-start line than on lines from service preferred If the terminal removes several of the most preferred by
central office but will fail placing low resistance tip-to-ring these will look idle to the the PBX looptest Where the second trial locates line without tip-to-ring short calls lines to the terminal will complete normally However as the number of ground-start the number of calls both placed out of service by closing tip-to-ring is increased failing from the first and the second trial also increases Eventually as the removal of circuits
service continues all traffic to the terminal will be blocked To remove ground-start line in hunting group from service call should be placed from or to that line
Where range-extension equipment is used in the network the loop test is not effective have Calls from the network over range-extension equipment which would experienced failures Such second trial without range-extension equipment give no-ring no-answer
calls are reduced in the 1/lA ESS and DMS-l0O switching systems when Uniform Call
Distribution UCD is used
6.2.10 DIrect inward Dialing
DID provides for direct-dial access to PBX stations or radio paging or voice mail stations DID transmission of address systems etc from public network requires signals of address from the network to the terminal Wink-start or delay-dial supervisory control office signals can be used depending on the serving switching In addition loop dial reverse-battery supervision is used While either loop or battery-and-ground pulsing
is used for address signals other forms of signaling such as multifrequency or DTMF are
is feature of the 1/lA and DMS available DTMF signaling to PBX ESS DMS-l0 Generic 301.80 or later 100F switching systems Section 6.13.5 The DMS-l0 system
allows for multifrequency and DTMF address signaling if the DTMF IN-OUT pulsing
option has been provided The DMS-200-type systems cannot be upgraded to provide
this feature The EWSD system provides DII using dial-pulse or DTMF signaling The
6-26 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue Apr11 1994 SIgnaling
NEAX-61E system provides DID using dial-pulse multifrequency or DTMF address signaling and loop or EM supervisory signaling Although DID is considered line signaling DID uses signaling identical to that of 1-way outgoing trunk In fact most in DID circuits connect to the trunk side of the switching system The principles used
DID signaling are covered in the following sections
Section Title
6.4.5 Immediate-Dial
6.5.1 6.5.3 Delay-Dial
6.5.4 Wink-Start
6.6 Dial-Pulsing
6.7 Loop Signaling
6.7.1 Reverse-Battery Signaling
6.7.2 Battery-and-Ground Signaling
service Any switching system that can provide tandem connections can provide DID This includes 1/lA ESS ESS 5ESS DMS-1O DMS-100F EWSD and NEAX-61E switching systems feature for making DID trunks busy automatically is available for the 1/lA ESS and ESS switching systems All require control circuit from PBX to the central office to signal when local power failure or PBX processor failure occurs
The PBX connects the tip and ring of the pair together when conditions are normal The
5ESS DMS-lO DMS-100 and EWSD systems do not have this feature However all have off-hook make-busy see Table 6-11 which can be used to busy-out DID trunks from the PBX An example of the terminal end when using loop reverse-battery signaling is shown in Figure 6-11 This is the arrangement for DID circuit in Rockwell Galaxy system
DID also provides direct-dial access to Centrex stations from the public network In this case the traffic is carried to the Centrex on network trunks The supervision and address signaling use any of the methods offered by the offices involved
6-27 BOC Notes on the LEC Networks 1994 SR-TSV-002275 1994 Signaling issue AprIl
Demarcatcn
Figure 6-11 Loop Reverse-Battery Signaling for DID
6.2.11 Coin Collect and Coin Return
and coin return uses Coin collect usually uses 130 negative-grounded potential for coin 130 positive-grounded However there are few locations using 130 and collect and 130 for coin return The circuit in simplified form for collecting
is returning coins over customers line is shown in Figure 6-12 Where 130 used current limiter or series dropping resistor is added to the circuit The value of the resistor is chosen so there is approximately 20-V drop across it when collecting or returning coins
diverts the coins in direction to collect and in The coin mechanism is polarized and one the other to return Contacts connect the coin magnets to ground when coin is deposited Operation of coin return signal from an operator-services system or automated coin-service system disconnects the talking battery and connects to 130 for coin-collect signal connects 110 to The collect or return signals are applied
minimum of 350 ma The minimum current required to operate coin relay is 41 mA
The Carrier facilities normally are used between the operator and the serving office sections methods of transmitting these signals on carrier facilities are described in the on
Operator Services Position System OSPS and the TOPS system coin control signals
Section 6.17 OSPS is feature of the 5ESS switching system while the TOPS system is feature of the DMS-l00/200F system
TOPS is trademark of Northern Telecom Inc
6-28 SR-TSV-002215 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Signaling
Subset
To Trans mission Circuits
Figure 6-12 Coin Collect and Return Circuit
6.2.12 Abandoned Call Line Snooper Feature
An ACD may send an answer-delayed announcement during busy-hour periods After this announcement is received the customer may become impatient and hang up before being cut-through to an attendant If the central office has calling-party control with
immediate disconnect full disconnect takes place However if the central office
equipment is of the joint-control or calling-party-control type and has entered its time-out line will period as result of the calling party going on-hook the ACD ground-start
continue to be locked to the originating office because of the off-hook fromthe ACD
It would be annoying to the attendant to try to answer such an abandoned call For this
reason when the circuit is selected at the ACD and before the attendant is connected the
holding bridge at the ACD is opened for about second If the calling party is still off-
hook the call will remain attached to the ACD If the calling party has gone on-hook the
call will be disconnected from the ACD
6.2.13 Showering
Showering is condition that occurs when the line current is of such magnitude that it
is sufficient to operate the line current sensor but insufficient to operate the customer
dial-pulse register current sensor register relay or ferrod The condition occurs because
the line leakage resistance is too low or terminal equipment draws more current than it
should in the on-hook condition The result is that the control circuits continue to
attempt to connect the line to the dial-pulse register while the dial-pulse register
repeatedly releases the line as if the call were abandoned
6-29 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling AprIl
Showering lines are problem in all switching systems that use line current sensors for call recognition and then switch to sensors in the dial-pulse register to supervise during the dialing interval In electronic systems the switching system will automatically remove the line from service The EWSD system among others solves the showering problem by using the same loop current sensor throughout the call setup
63 Interoffice Signaling
This section describes interoffice signaling for operator and customer dialing
The names given for the various signals are those that are well established by general use
few alternative terms having considerable use are shown in parentheses in Table 6-6
The direction of each signal the indication given to the customer or operator and the on or off-hook classification of the signal are shown where applicable
6-30 SR-TSV-002275 BOC Noes on the LEC NetworksI 994
Issue AprIl 1994 SIgnaling
Table 6-6 Signals Required in Dialing Through the Network
D ctioc
On- Off- affing Called To To See
Nneorsigcal Rook Hook End End UeeorMcing Oistoo Operator Note
Requests senice end holds Selns
DleI Tone Eqtdpment for ing Steady tone Steady tone
No eeMoe deed
TIP lighted Release .ealon
Mrer Called patty aratwere Called end 06-Hock charge limg begine cry lamp datt d.ps..dsonlttsulal
HangUp Called party releaset Dela elay Pielng Called end ready for 6glts Slait-otal or torwaid lamp dark
Called end not ready for ta Stat-al or KP tonsaid bs dark
Called end reedy for otts Slatdal or
Start
Dial Ptdig DP Indlastos called rerther
Dual-Tone Inotcatee called nimter
Pdelng
Pi.dslng MF Keypate KP Prepares reoelver for dglts
Digits celled mjber
Start Si Indeates that all necessary
otgfts have been sert
Start IdentIficatIon Indicates that Centallzsd Auto AutomatIc madc Message CAMA
Nber Iden sender is reedy to receive flcatlon ANI ca mmther
ANt Oulpijaing
Keypilse -e- Prepares CAMA sender for dIgIts
IdentIflon -e Indicates if service-obseived
Digits whether IdentIficatIon la auto mad ANt or operator teilure hoteVmo mcblle cabless _c et
Digits -e- Indicates cs5ng rarth sent
Start Pe -e Itcatea all glts sent
604PM tone Line-Busy Tone Called line busy 4rlen- tons ntn per OPtI
Reorder Tone All paths busy 1204PM tone 1204PM tone and No CircuIt All trxe busy
All Tnse Busy Blodeege In eqtipment
IncoeTleta regislralktn ol digits
--e Alerts called oJetomer to Bell tnge or IncomIng call
6-31 BOC Notes on the LEC Networks 1994 SA-TSV..002275 1994 Signaling Issue AprIl
Table 6-6 Signals Required in Dialing Through the Network Continued
Direcdos Indicedos
To To See On- Off- Callini Called NanofSigcal Hook Hook End End UieorMceeln Custonr Opasr Note
Audible ranging Called station being ning or awalng ogem an Ringing tone
Ring Foment Recalls operator fotward to Steady or flashing filmed Wink isnE
for Ringh Recalls operator backward to Lighted lanD Undme coeon di.satlcn of ring
Ringing Start ng when egument is of controlled ringing
Pgpe
Relsase customer from operator
Reverse Make- Make busy from far end of trunk busy
Coin Collect To collect coins deposited hi coin box
Caning Card lncates caller may dial bOing Service Tone flUff5f
Coin Collect Indicates coin collect signal Is tone or no Tone being sent to coin box tone
Coin Return To return coins deposited in coin box
tone or no Coin-Return Indicates coin return signal Is High Tone 0-- being sent to coin box tone
Coin-Denon Indicates nwvters and vetues Tones from gongs or oedhlstor in hiatlon Tone of coins deposited hi box coin box
Indicates to operator dass 01 HIgh lowor no
Tone service of calling customers tone line
Recorder Warn Indicates telephone conversation tone ing Tone bo recorded of 0.5-second duration
everg 15 seconds
440te tone Alerting Tone Indicates that operator has come on line emergency intern for seconds on busy line verification call followed by 1/2 second of tone evesy 10 seconds Recall Cust -e Manually recalls operator Rashing lanp omer Resting to connection
Note An ST pulse may not be sent on calls by multiparty customers or in the case of identification failure
Note Conditions producing 120-IPM tone signal apply to facilities that are engineered relatively liberally
hence the probability of an immediate subsequent attempt succeeding is good terminal Note Ringing of the called station should be started automatically upon seizure of the called
Note No effect unless Inward operator is at terminating end of the connection
Note 60 ms of 9411477 Hz number tone and 940 ms of 350 440 Hz dial tone This signal decays
exponentially with time constant of 200 ms
6-32 SR-TSV-002275 BOC Not. on the L.EC Networks 1994
Issue Apr11 1994 Signaling
connection Applications of several of these signals are listed in Table 6-7 for dialed
switched through two intermediate offices in addition to the originating and terminating offices Calls can of course be switched through more or fewer offices
Section 6.4 describes on- and off-hook signals from technical viewpoint as well as how they are used in signaling systems The requirements for sender and register timing intervals are also included in this section
The signaling carrier and switching systems referred to in this section are manufactured by ATT NEC Northern Telecom Alcatel Ericsson and Siemens Stromberg-Carlson There are many systems of other manufacturers in use throughout the industry Some of these differ appreciably in design but are comparable with the equipment described in this section
North American Signaling on international circuits to points outside the contiguous network uses systems different from those in domestic service At present most such circuits terminating in the United States use the International Telegraph and Telephone
Consultative Committee CC1TF Signaling System No.6
that makes Digital carrier systems for example Ti have an integral signaling system use of one of the code bits associated with each channel for trunk signaling These
systems can interconnect with EM lead loop reverse-battery and foreign-exchange that have signaling They can also connect directly with switching systems digital
carrier trunk feature
6.4 On- and Off-Hook Signals
number of interoffice signals are classified as on-hook off-hook or sequential
combination of the two The terms were derived from the position of an early telephone
receiver in relation to the mounting hook provided for it If the station is on-hook the
conductor loop between the station and end central office is open and no current is
flowing For the off-hook condition there is dc shunt across the line and current is
flowing in the loop For more information on interoffice signaling see TR-NWF-000506
Signaling Sections 6.1 6.4.2
The CC1TF is now called the International Telecommunication UnionTelecommunication Standardization Sector ITU-T
6-33 BOC Notes on the LEC Networks 1994 SR-TSV002275 Issue 1994 Signaling April
Table 6-7 Signals Used in Dialing Through the Network
Orlginalthz -g Tg Oddng T.sdrin Eed Called Not Office Office Office Office Staicc Reuika Name of Signal Sedon
Connect Seizure
-4- DI.sconnect 4- -4 12 234 Answer Off-14001
I4agJJp 4- 24
DelayDlal Delay Pulsing As requited
SWt.DlaI Ss1 PulsIng
Wkik-Siazt
Dial Tone
CaSed-Station Identity DTMF Pulsing
Dial Pulsing DP MultlfrequencyMF
Pulsing
CaSing-Station
Identity CAMA Verbal lnteflm revx Identification MF Pulsed Digits tic lentificata
uneBusy
Reorder Tone SIT 4-
No Circuit NC Tone Sri Inbatandern
Ringing
Mdtle Ringing
As Ringing Stall required
Recorder Warning Tome As required
AnnouncementS 4- 6.7
the called station In Note In ground-start operation the connect and disconnect signals extend to loop-
start these signals extend only to the tertrinatlng end office
Note The signal is relayed from office to office
Note Used in charging control
It Is desirable to return Note Answer supervision must be returned to the office where charging Is located
real or simulated answer supervision to the originating office in all cases ahead Note Connection must be established before remaining or regenerated digits are sent
Note at of the Indicated offices May originate any one Note Announcement may be by machine recorded announcement or operator
6-34 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SignalIng
These terms are also convenient to designate the two signaling conditions of trunk
Usually if trunk is not in use the offices at both ends are sending an on-hook signal
Seizure of the trunk at the calling end sends an off-hook signal toward the called end If
trunk is awaiting an answer from the called end the called end is signaling on-hook
toward the calling end Answer of the call sends an off-hook signal back toward the
calling end However one-way trunks using delay-dial operation with loop reverse-
battery signaling can send off-hook toward the originating office when idle
Both off- and on-hook signals when not used to convey address information are often
referred to as supervisory signals or simply as supervision sequence of alternating on-
and off-hook signals dial pulses occurring within specific time duration may be used
to convey address information
The various on- or off-hook signals are shown in Table 6-6 The direction of
transmission of each signal is also shown The following factors help in determining the
significance of signal in addition to information in the table
Duration The on-hook interval of dial pulse is shorter than an on-hook
disconnect signal transmitted in the same direction
Relative before time of occurrence delay-dial off-hook signal occurs any digits
have been sent while the answer off-hook signal occurs after all digits have been
sent Although both signals are transmitted in the same direction and both are off-
hook they are distinguished by the relative time of their occurrence
6.4.1 Connect Seizure
connect signal is sustained off-hook signal sent toward the called end of trunk
its seizure This is the which the end following signal means by calling requests service
The signal continues as long as the connection is held Momentary interruptions in the connect signal caused by dial pulses are ignored as far as the connect and disconnect functions are concerned To avoid double seizures that is simultaneous seizure from both ends connect signal must be sent immediately upon seizure of 2-way trunk to make it busy at the other end Such seizure of 2-way trunk is called g1ire See Section 6.5.5
6.4.2 Answer Off-Hook
6.4.2.1 Charge Delay
called When the customer answers an off-hook signal is sent toward the calling end to the office automatic takes where charging place For charging purposes the answer off- hook signal is distinguished from off-hook signals of shorter duration by the requirement that it be continuous for minimum interval ranging from to seconds The minimum
35 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling April
should be as an answer value stated in the LSSGR for an off-hook signal that recognized
and is seconds signal for charging supervision purposes
customers transmit an Most trunks when idle and all trunks when awaiting the answer trunks return to the on-hook on-hook signal from the called end to the calling end Most state when the called station hangs up
6.4.2.2 Answer Signals on Calls to Directory Assistance
be returned all 555-1212 and To provide proper billing answer supervision should on
NPA 555-1212 calls for direct-dialed directory assistance Where operator directory calls and assistance 131 trunks are used jointly to complete customer-dialed 555 Where operator-placed 131 calls they should be arranged to return answer supervision
is the 131 minks handle only operator-dialed traffic the return of answer supervision optional
6.4.2.3 Cross-Office Transfer Time for Answer Signals
Since individual switching offices contribute directly to network effects it is important to
which the network is establish performance objectives that recognize those parameters to most sensitive Cross-office delay in transfer of the answer signal is one such parameter attributable slow transfer of the Long-term priorities seek to avoid loss of revenue to answer signal that governs the start of charging
from to Return of an answer signal should be performed with dispatch Figures ranging
25 ma are being achieved and are preferred In the absence of economic options to for normal tandem offices achieve higher speeds figures on the order of 50 ma average appear acceptable
6.4.3 Control of Disconnect
6.4.3.1 Calling-Customer Control of Disconnect
Calling-customer control of disconnect also known as forward control of disconnect which the end forward disconnect or calling-party control is the means by calling notifies the called end that the established connection is no longer needed and should be released Forward disconnect is an on-hook signal sent toward the called end As long as the customer remains off-hook the connection will remain up When the calling
connection is customer goes on-hook for period longer than the disconnect time the released This allows the caller to disconnect at any time by hanging up
on-hook To distinguish an on-hook signal intended as disconnect signal from other 150 400 signal indications the forward disconnect signal should exceed about to ma To ensure that ring-forward signals do not cause false disconnects incoming trunk
6-36 SR-TSV-002215 BOC Note on th LEC Networks 1994
issu AprIl 1994 Signaling
release on-hook interval of equipment to operators must not during minimum 140 ms
maximum 130-ms ring-forward pulse plus 10-ms safety margin In general any
trunk circuit connected to inband signaling equipment must also be arranged so that it
will not release during an on-hook interval of less than 140 ms
Calling-customer control is usually modified by the end office to prevent connecting the
called dial the caller and the party to tone as soon as goes on-hook to prevent locking
caller to the connection as long as the caller is off-hook Table 6-8 lists disconnect
timing that occurs in various telephone connections when the calling party hangs up and
the called party remains off-hook and when the called party hangs up and the caller remains off-hook
Calling-customer control of disconnect is also modified by the Automatic Message Accounting AMA location local AMA Centralized Automatic Message Accounting and tandem OSPS or TOPS system by some switching systems If the called
party goes on-hook for period of time after at least seconds of answer timed disconnect will occur Current arrangements for Local Automatic Message Accounting
LAMA CAMA operator-services systems and some tandem switching systems requireanon-hookfromthecalledpartyofl0tol2 secondstocauseathned disconnect
Table 6-8 Disconnect Timing
For non-coin direct-dialed calls no operator handling
Central Timed Delay In Terminating Timed Delay In Originating Office Office from Incoming Office From Incoming Switching Disconnect to Restoral of Disconnect to Restoral of
System Called Line to Idle State Calling Line to Idle State
1/lA ESS to seconds ground-start Immediate ground-start outgoing unk
10 to 11 seconds loop-start 10 to 11 seconds loop-start
2/2Band5ESS lOtoliseconds lOtoliseconds
DMS-lO 11 seconds 11 seconds
DMS-l00 10 seconds 10 seconds
EWSD 10 seconds software adjustablet 10 secondst
NEAX-61E 10 seconds 10 seconds
L.SSGR 10 to 12 seconds 10 to 12 seconds
From 128 ms to 155 seconds in 128-ms steps software-adjustable
From to 40.8 seconds in 10-ms steps software-adjustable
From 10 to 12 seconds in 0.1-second steps software-adjustable
Overload conditions will reduce the timed disconnect period to seconds in the 1/lA ESS switching system The disconnect releases all equipment from the LAMA
CAMA operator-services system or tandem switching location to the called party The
6-37 BOC Notes on the LEC Networks 1994 SR-TSVOO2275 SignalIng Issue April 1994
of the connection fromthe the location tandem portion calling party to AMA or switching system may remain connected or may be disconnected as covered in this section
The disconnect timing in LAMA CAMA operator-services systems and tandem be than the disconnect switching for the called party going on-hook should much longer
for the on-hook This is because short on-hook timing calling party going many signals
are generated in the network in the backward called-to-calling direction There is no
plan to reduce the disconnect timing for called-party disconnect below the present 10 to
12 seconds This form of disconnect releases the calling party and stops charging when
carrier facility used in the connection fails
Hold forward no timed disconnect after 2-second answer is no longer required This
means that test positions can no longer hold forward on calls that have been answered
However it is still possible to hold forward on calls that are not answered
6.4.3.2 Calling-Customer Control of Disconnect with Forced Disconnect
In addition to the features discussed above calling-customer control of disconnect can
include forced disconnect feature The addition of this feature is distinguishing characteristic of outgoing CAMA and Automatic Intercept System AIS Section 6.20 end office trunk circuits The calling customer may disconnect at any time but is automatically disconnected winked off when an on-hook signal is received from the and other disconnect CAMA or MS The tinting of partial dial permanent signal
sequences is performed by the CAMA or MS trunk to avoid holding trunks out of
service If the terminating end reverts to off-hook the outgoing trunk circuit is automatically made busy reverse make-busy
The forced disconnect described in the previous sections is timed by the CAMA or OSPS times operator-services office For example on called-party disconnect
is butthe default 10 seconds on non-coin calls the TOPS system as CAMA adjustable is 16 seconds and the 4ESS switching system as CAMA times 10 seconds before returning an on-hook signal to the originating and terminating offices The originating office should eliminate the disconnect timing per Table 6-8 when the CAMA or operator-services system goes on-hook first The originating office must however time long enough before disconnect to prevent accidental disconnection Minimum disconnect timing of 150 ma is long enough for CAMA trunks Operator-services trunks that use multiwink coin control or expanded-inband coin control would require longer disconnect times Many originating offices use 190 to 425 ma disconnect timing The on-hook wink used in expanded-inband coin control is 300 to 450 ma when received
This requires disconnect time of more than 500 ma
Wink off and winked off are popular terms for forced disconnect from CAMA AIS or operator-
services system Actually the off- to on-hook transition not wink causes the disconnect
4ESS is trademark of ATT
6-38 SR-TSV-002275 BOC Not. on the LEC Networks 1994
Issue Apr11 1994 SIgnaling
6.4.3.3 Operator Control of Disconnect
Operator control of disconnect is used on outgoing trunks to operator-services systems
The end office trunks are designed to have calling-customer control of disconnect until the operator office returns off-hook supervision Automatic Number Identification receive the request to the end office to indicate that the operator office is ready to calling of the the number This off-hook signal remains for the duration call locking calling customer to the operator office At the end of the call the operator office recognizing an and then reverts to on-hook from the calling or called party provides necessary timing on-hook toward the end office This causes forced disconnect of the calling customer
If the terminating end reverts to off-hook the trunk circuit is automatically made busy
6.4.4 Guard Time
Generally two methods are used to guarantee the minimum disconnect interval necessary interval between calls In the first method the trunk is held busy at the calling end for an after its release This prevents new connect signal from being sent forward until sufficient time has elapsed to effect the release of the equipment at the called end The second method permits the trunk to be reseized immediately but the sending of the connect signal is delayed by common-control equipment either for measured interval or until test of the trunk indicates that disconnection has taken effect The second method cannot be used for 2-way trunks because as explained in Section 6.4.1 the connect signal must be sent immediately
The timed interval used to ensure trunk release before reseizure is called guard time The disconnect tune averages 360 ma Therefore typical guard times are 700 ma Minimum guard times for senders are chosen to be longer than the average disconnect times plus round-trip signaling time for the incoming office but generally not as long as the maximum possible disconnect interval guard time less than the maximum possible disconnect interval is used to save sender holding time This can be done without an appreciable effect on service because trunks do not usually take the maximum time to release new call is not usually connected in the minimumtime and signaling distortion is not normally at its most adverse limit
The actual guard times for the various switching systems are in Table 6-9 The table includes guard times for use on terrestrial facilities and for use on trunks routed through an earth satellite where the switching systems can work with such facilities The 1/lA ESS 1/lA ESS HILO 4ESS and 5ESS DMS-10 and DMS-lOOF switching with systems have options to operate sateffite facilities
ilLO is feature of the 1/lA ESS switching system for toll use It provides two electrically independent
transmission paths through the switching network and thus provides 4-wire transmission in 2-wire switch
6-39 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling issue April 1994
Table 6-9 Actual Guard Time for Various Switching Systems
Guard Time in
Milliseconds
Switching Terrestrial Satellite
System Facilities Facilities
1/lA ESS and
1/lA ESS HILO 800 to 1000 1600 to 1800
2/2BESS 750 mjn 4ESS lO5Oto 1200 lO5Oto 1200
5ESS 800 to 1000 None
DMS-10 128 to 3968 128 to 3968
DMS-100F 10to2550t 10to2550t
EWSD 752 10001 752 10001
NEAX-61E 1000 None
ISSGR 750 to 1000 None
Except when timing list entry is not available guard time is then ms
trunk in Adjustable per group 128-ms steps
Adjustable per trunk group in 10-ms steps
1000 ms for immediate-dial and stop-go trunks 752 ms for the rest
Switching systems using guard timing do not require an on-hook from the far end between an outgoing call and an incoming call on 2-way trunk Switching systems in the network should hold 2-way trunk busy to another outgoing call for period of time guard time after the disconnect on-hook signal is sent to the far office This permits
far the idle condition office does have the switching system to restore to The far not guardtime afterthereleaseofanincoming call Asaresult the farofficecanoriginatea new call before the guard time has ended in the outgoing office The effects of this are that the two offices tend to alternate originating calls on given trunk during peak traffic periods and glare the simultaneous seizure of both ends of 2-way trunk is reduced
Switching systems are blind to the supervisory stale during guard timing Therefore it is not necessary to see an on-hook between an outgoing and an incoming call If an off- hook is present when the switching system completes guard timing the off-hook should be treated as new call
40 SR.TSV-002275 BOC Noes on the L.EC Networks 1994
Issue AprIl 1994 SignalIng
An important factor in establishing compatible guard time is the interval required to restore the incoming trunk circuit to the idle condition force an on-hook toward the
the disconnect is received the calling end if the called end is still off-hook after signal by intervals that incoming trunk Electronic switching systems in general have disconnect the trunk can become very long for heavy traffic conditions The time required to restore circuit to idle after the disconnect timing has elapsed is shown in Table 6-10
Table 6-10 Time to Restore Trunk Circuit to Idle after Disconnect
Light Heavy
Switching Traffic Traffic System ms ms
1/1AESS 175 to 275 450
2/2B ESS 400 None 240 270 4ESS ring forward allowed 175 to
4ESS ring forward not allowed 175 to 320 350
5ESS 100 180 at 95% level 250 max DMS-10 200 200to300
DMS-100F 100 180 at 95% level 250 max EWSD 50 300 max
LSSGR None None
The guard time discussed in the last few paragraphs is the time that the 2-way trunk is held idle after disconnect This guard time historically was not applied when digits were not received after the connect signal The common control of trunks in electronic switching systems rather than control in the individual trunks increased the switching circuit delay Single-frequency signaling and earth satellites increased the facility delay With the increases in these delays pumping was experienced on 2-way trunks As
all disconnects result it was necessary to apply guard time on to prevent pumping
6-41 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling April
condition Pumping on 2-way trunks is started by the disconnect of call or by facility
idle think The is sustained the that causes signaling bit on an pumping by recognition in the of delay-dial or wink-start signal as new connect signal long delays signaling received As follows path and no guard time after connect signal when no digits are
Off-hook signaling hit to office
Office sees signaling hit as connect signal sends wink-start signal wink- to office Office sees the
start signal as
connect signal
Signaling hit ends
Office restores trunk to idle
Office sends wink-
start signal to
Office
Office Asees the wink-start as connect signal
Wink-start signal from
Office ends
Office restores trunk
to idle
Office sends office
wink-start signal Office sees the
wink-start signal as
connect signal
each At this point the pumping will continue indefinitely with offices and sending other wink-start signals
connect for This application of guard time causes the trunk circuit to ignore new signal
period of time after the release of an incoming call The guard time should be as long as the round-trip signaling time of the facility to be completely effective The 1/lA ESS and 4ESS systems have effective guard times when an incoming call is released The 1/lA ESS switching system guards only after an incoming off-hook/disconnect sequence time for the where no digits are received The guard time used is equal to the guard disconnect of an outgoing call
6-42 SR-TSV-002215 BOC Notes on the 1.EC Networks 1994
Issus April 1994 SIgnaling
The 4ESS DMS-1O and DMS-100F switching systems provide the same guard time when an incoming call is released as when an outgoing call is released See Table 6-9 for details Not all switching systems provide an effective guard time for new connect signals after the release of an incoming call However guard times much shorter than optimum often stop pumping Moreover short guard time can be obtained in some systems by switching from delay-dial to wink-start operation As indicated in Table 6-
13 the return of wink-start signal is much slower than the return of delay-dial signal in many systems This often prevents pumping on circuits that pump when operated delay-dial
6.4.5 Immediate-Dial
Trunk groups employing common receiving equipment such as registers may be equipped at the called end with fast links or bylinks with both the links and the common receiving equipment liberally engineered to minimize delays Such groups are normally ready to receive pulsing about 120 ms after receipt of the connect signal
Immediate-dial is used with these trunks The NEAX-61E system is ready to receive pulses 65 ma after seizure Advantage is realized however if delay-dial is employed for signaling-integrity-check purposes Senders are informed by translations whether they are operating with this type of trunk or with trunks requiring either delay-dial or wink- start signal prior to the start-dial indication
As minimum interval between seizure and outpulsing on immediate-dial circuits the
1/lA ESS switching system is using 170 ma the 4ESS switching system 210 ma and the 150 waits 192 before 5ESS switching system ins The NEAX-61E system ma sending pulses and the EWSD switching system delays 200 ma The DMS-l0 and
DMS-100F switching systems have an adjustable predial delay that can be set to 150 ma or higher The Galaxy System terminal equipment has minimum of 150 ins predial delay
6.4.6 SignalIng Integrity Check
Signaling integrity check is per-call test made by an office during the initial call setup
It is used as an indication of the ability of the trunk to transmit signals The test is associated with detection identification and recording of trunk/facility troubles as well as with second attempt at call completion if the switching system has this capability
The ability to detect trunk/facility troubles lessens the probability that customers will be left circuit service high and dry for example held out of with no batteiy or ground on tip or ring and improves the call completion rate when the switching system has second- attempt capability The ability to identify and record trunk/facility troubles greatly assists maintenance Therefore the integrity check feature is recommended on intertandem and tandem connecting trunks
The exact nature of the check varies between switching systems However there are two general types of signaling integrity checks The first and most complete check requires
63 BOC Note on the LEC Networks 1994 SR-TSV-002275 Signaling issue Apdl 1994
response from the incoming office in the form of delay-dial or wink-start signal and is
called an integrity check The second check for wire trunks only requires circuit
continuity and the correct polarity on the tip and ring of the trunk and is called
continuity and polarity check
The 4ESS 1/lA ESS DMS-1O and DMS-100F switching systems provide the continuity
facilities and polarity test check on immediate-dial calls over physical using loop
reverse-battery supervision
Trunks using immediate-dial not equipped for integrity check over carrier do not have the machine any form of signaling-integrity check Under these circumstances switching undetected outpulses blindly on the trunk If there is trunk trouble it generally goes by
the equipment no trouble record and the customer usually ends up high and dry
The 4ESS 1/lA ESS DMS-lO and DMS-100F switching systems can provide signaling calls the wink-start method of integrity check on all outgoing using delay-dial or
operation with multifrequency pulsing and loop reverse-battery or EM supervision
This method can also be employed with dial-pulsing and EM supervision provided the
distant office uses an incoming trunk circuit that will return stop-dial/start-dial signal
The Galaxy System terminal equipment can provide signaling integrity check on all
outgoing calls using delay-dial or wink-start
6.4.7 Reverse Make-Busy Off-Hook Make-Busy
Outgoing trunk make-busy by means of off-hook supervision received from the
terminating end is feature of outgoing CAMA operator-services system and AIS
trunks in all local switching systems Other types of outgoing trunks especially loop
signaling trunks with customer control of disconnect require an applique circuit to make
the trunk automatically appear busy when idle and while receiving off-hook supervision
from the terminating end
and Provisions for off-hook make-busy for trunks other than operator-services system
AIS when an outgoing trunk circuit is used or other techniques that accomplish the same
result with or without an outgoing trunk circuit are summarized in Table 6-11
6.5 Controlled Outpulsing
Controlled outpulsing is used between offices and between operator-services systems and
offices Controlled outpulsing permits the use of slower links and results in more efficient use of registers With controlled outpulsing the originating office seizes the trunk and sends connect signal to the terminating office just as in immediate-dial outpulsing However if the idle state of the called office is an on-hook indication the terminating office returns an immediate off-hook signal or is off-hook idle followed by an on-hook signal to the originating office The exact timing of the on- off- on-hook or off- on-hook signaling sequence constitutes the differences between the delay-dial and
6-44 SR-TSV.002275 BOC Notes on the LEC Networksi 994
Issue April 1994 SignalIng
wink-start methods of controlled outpulsing For more on controlled outpulsing see TR
NWT-000506 Signaling Sections 6.1 6.4.2
Table 6-11 Off-Hook Make-Busy Provisions
For trunks other than operator-services and Automatic Intercept System
Provision
Off-Hook of Off-Hook
Office Supervision Make-Busy Make-Busy
Loop No None Available 1/lA ESS EM No Substitute 2-way
trunk circuit
Loop or EM No Substitute 2-way 2/2B ESS trunk circuit
4ESS EM No Substitute 2-way
trunk circuit
Yes available 5ESS system Loop EM digital Always available DMS-1O Loop EM digital Yes Always available DMS-100F Loop EM digital Yes Always
single-frequency
available EWSD Loop EM digital Yes Always Yes available NEAX-61E Loop EM digital Always
These differences are described in Sections 6.5.1 through 6.5.4 Whether delay-dial or wink-start the originating office will wait short period after receiving the on- off- on- Either hook or off- on-hook signaling sequence and then begin outpulsing dial-pulse or multifrequency address signaling can use controlled outpulsing Essentially all new trunks being added to the network that require controlled outpulsing use the wink-start signal
To describe the operation of the various switching systems for signaling-compatibility purposes properly it is necessary to define the signal sent by the terminating office and the signal expected by the originating office Generally the signal sent by the terminating office is the same as the signal expected by the originating office However this may not always be the case In addition in specific situations there are advantages in not having the sent and expected signals identical For example glare resolution in the
1/lA ESS switching system Section 6.5.5 uses different sent and expected signals to resolve the glare in the wink-start mode When two 1/lA ESS switching system offices interconnect both can send wink-start but both do not expect wink-start The office selected to back out of the connection glare situation expects wink-start signal
is and therefore times the wink Any wink-start signal over 500 ms detected as glare does time the The office selected to remain on the trunk expects delay-dial and not signal
6-45 SOC Not. on the LEC Network 1994 SR-TSV-002275 issue April 1994 Signaling
received other than the 18- to 20-second interval timing and therefore remains in various control of the trunk Another factor is the difference in the definition used by the
the of the systems for delay-dial and wink-start Table 6-12 covers design capabilities various systems the systems ability to use the various methods and the preferred method of controlled outpulsing
6.5.1 Delay-Dial Without Signaling Integrity Check
is the oldest method of controlled Delay-dial without signaling integrity check outpulsing It is also the least satisfactory method from maintenance standpoint wink-start with check Consequently it should be used only when or delay-dial integrity
is not available
which In this method the originating office seizes the trunk circuit sends connect
After interval of at least 300 on some minks signal toward the called office timing ma from the called and 75 ma on others the calling office then looks at the supervision
office If the supervision is on-hook the originating office starts outpulsing procedures the from the If the supervision is off-hook the calling office waits until supervision called office sends called office goes on-hook start-dial then starts outpulsing The the connect delay-dial off-hook signal from the incoming trunk circuit as soon as signal
until is attached is recognized The called office maintains the delay-dial signal register start-dial to the incoming trunk When the register is ready to receive pulses the on-
hook signal is sent to the calling office
In this method of controlled outpulsing there is no minimumtime requirement for the
if the called office is delay-dial off-hook signal In fact no delay-dial signal is needed
ready to receive pulses
If the called office is not ready to receive pulses the speed with which the called office
is Where check is returns the delay-dial signal especially important signaling integrity
not used the failure to receive delay-dial signal may permit the sender to outpulse the call be routed to before the register is attached at the called end This can cause to
reorder or left high and dry depending on the exact conditions involved
46 SR-TSV-002275 BOC Note on th LEC Networks 1994
Issue April 1994 SignalIng
Table 6-12 Available Controlled-Outpulsing Methods
Dday-Dtal With
Integrity
Delay-Dial check Wink-Start
Switching Sent
System Type of Call Expect Hardware Software Expect Expect Sent
lilA ESS Non-toll 2-way soup NAN NNN NNN NAN PAG PAN
End Office
Tandem connecting NAN NAN PAN
incoming
Tandem connecting NAN PAN
outgoing
CAMA outgoing NAN PAN
1/lA ESS 2-way intertandem NNN NNN NAN PAG PAN Tandem
Tandem connecting NNN PAN
incoming
Tandem connecting NAN PAN
outgoing
1/lA ESS 2-way intertandem NAN NAN PAG PAN mLO
Tandem connecting NAN PAN
incoming
Tandem connecting NAN PAN
outgoing
CAMA incoming PAN
2t2B ESS Non-toll incoming NNN PAN
Non-toll outgoing NAN PAN
Tandem connecting PAN
incoming
Tandem connecting NAN PAN
outgoing
CAMAoutgoing NAN PAN
4ESS 2-way intertandem NNN NAN PAG PAN
Tandem connecting NNN PAN
incoming
Tandem connecting NAN PAN
outgoing CAMA NNN PAN
5ESS system 2-way Non-toll NNN NAN PAG PAN
End Office
Tandem connecting NAN PAN
incoming
Tandem connecting NAN PAN
outgoing
See Legend at end of table
6-47 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling issue AprIl 1994
Table 6-12 Available Controlled-Outpulsing Methods Continued
Dthy.Dlal with
Integrfty
Delay-Dial Check Wink-Start
Swltthlng Sent
System Type of Call Expect Hardware Software Expect Expect Sent
5ESS system 2-way intertandem NAN NAN PAG PAN
Tandem Tandem connecting NAN PAN
incoming
Tandem connecting NAN PAN
outgoing CAMA PAN
DMS-lO and 2-way Non-toil NAN NAN PAG PAN
DMS-100F Tandem connecting NAN PAN
incoming
Tandem connecting NAN PAN
outgoing
2-way intertandem NAN NAN PAG PAN
CAMA incoming NAN PAN
CAMAoutgoing NAN PAN
EWSD Non-toil 2-way NAN NAN PAG PAN
End Office Tandem connecting NAN PAN
incoming
Tandem connecting NAN PAN
outgoing
CAMA outgoing PAN
NEAX-61E 2-way non-toil NAN NAN PAG PAN
End Office Toil connecting NAN PAN
incoming
Toil connecting NAN PAN
outgoing CAMA
NEAX-61E 2-way intutandem NAN NAN PAG PAN
Tandem Tandem connecting NAN PAN
incoming
Tandem connecting NAN PAN
outgoing CAMA PAN
..egend
First Character PPreferred method Not premed method
Second Character Always Available
Not always available
Third Character Preferred method used when trunk will back-out of glare conditions
Not used when trunk does not back-out
No glare resolution consideration
6-48 SR-TSV002275 BOC Noes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
The trunk circuits that use EM leads for signaling in the delay-dial method of operation are on-hook at both ends when idle EM signaling trunks should receive the delay-dial signal less than 300 ins after seizure otherwise the originating end will interpret the on-hook signal or lack of off-hook signal as start-dial signal and begin outpulsing prematurely The 300 ms must include all delays in signaling units and transmission circuit conditions facility as well as the delay within the terminating trunk These obviously preclude using transmission facilities derived from synchronous satellite that has round-trip transmission time of over 300 ms
Some loop signaling trunks using the delay-dial method of controlled outpulsing must receive the delay-dial signal within 75 ms of trunk seizure With this method of operation the incoming trunk is in the off-hook state when idle to meet the timing requirements Other loop signaling trunks using the delay-dial method must receive the seizure With this the trunks be signal in less than 300 ins after operation incoming can either off- or on-hook when idle The off-hook when idle trunk circuits could be used with synchronous satellite-derived facilities however the use of such trunks on satellite facilities is remote since the 2-wire loop trunk circuits are generally used for tandem connecting and there is no suitable signaling unit to interface with the 4-wire loop trunk circuits The 5ESS digital switching system does not provide off-hook when idle
When the originating office expects delay-dial signal without integrity check the terminating office may or may not send delay-dial signal The 1/lA ESS 1/lA ESS and send HILO 212B ESS 4ESS DMS-l0 DMS-100F switching systems can delay- dial signal These switching systems and OSPS never operate in the expect delay-dial without integrity check mode
Delay-dial is often referred to as an off-hook on-hook signaling sequence The delay- dial signal is the off-hook interval and the start-dial is the on-hook interval ATT-made switching systems do not check for an on-hook before the delay-dial signal The DMS have feature 10 and DMS-100F switching systems reverse off-hook make-busy They both check for an on-hook before seizure
6.5.2 Delay-Dial with IntegrIty Check
With integrity check the originating office will not outpulse until delay-dial off-hook signal followed by start-dial on-hook signal has been recorded at the originating office This method is very much like wink-start operation The 5ESS switching system always provides delay-dial with integrity check Electronic switching systems do have differences between delay-dial expected and wink-start expected
In the delay-dial with integrity check method of controlled outpulsing seizure of the trunk by the originating office causes the distant office to return delay-dial signal
However the delay-dial signal does not have to be returned within given interval that is 300 ms It can be delayed for longer period since the originating office will not begin outpulsing until it has received an off-hook delay-dial signal followed by an on- hook start-dial signal Performance of this positive signaling sequence from on-hook to off-hook to on-hook verifies the integrity of the trunk
6-49 BOC Notes on the LEC Networks 1994 SR-TSV002275 Issue 1994 Signaling AprIl
must meet the The delay-dial signal in this method of controlled outpulsing following requirements
The off-hook must be minimumof 140 ms in duration
The off-hook to on-hook transition start-dial must not occur until 210 ms after the
is receive connect signal is received and the register ready to pulses
the off-hook on-hook It is desirable to minimize the post-dialing delay by sending to The transition as soon as possible after the above requirements are met signaling system used with the transmission facility will distort the off-hook delay-dial signal as it is off- transmitted between offices As result the originating office must recognize an hook as short as 100 ms as delay-dial signal
210-ms from the of the It was not originally necessary to specify delay reception
office the of the start-dial because it connect signal at the terminating to sending signal with the advent was inherent to the operation of the ESS switching system However
it the 140-ms minimum of faster systems would be possible to complete sending delay- the dial signal before the originating office was in position to receive delay-dial signal sends the There is period of time after the 1/lA ESS switching system connect signal
forward on 1- or 2-way trunk during which the system is blind to signaling from the far of the be missed end start-dial signal occurring within 210 ins connect signal can
The 5ESS EWSD DMS-10 and DMS-100F digital switching systems have no blind
interval
Electronic switching systems 1/lA ESS 1/lA ESS HILO 2/2B ESS 4ESS 5ESS
DMS-l0 and DMS-100F can expect delay-dial with integrity check There is
difference between expect wink-start and expect delay-dial with integrity check Expect in delay-dial with integrity check operation has no time limit for the delay-dial signal while most systems except 4-second limit when glare detection is used Section 6.5.5 wink-start has shorter time-out interval of 500 to 600 ms for the 1/lA ESS switching
system See Section 6.5.5 for the time-out interval for other systems The 2/2B ESS
system times seconds 10 percent for an off-hook and then up to 16 seconds 10
percent for an on-hook
Delay-dial with integrity check can be on- off- on-hook like wink-start or an off-hook
on-hook signaling sequence like delay-dial All EM trunks are on-hook when idle The loop trunks can be off- or on-hook when idle per Section 6.5.1 The originating office would have to restrict interconnection to on- off- on-hook sequence trunks to
make use of all three signaling intervals However 1/lA ESS 1/lA ESS HILO
2/2B ESS 4ESS and 5ESS equipment does not detect the original on-hook DMS-10
and DMS-100F systems do check for the original on-hook
6O SR-TSV-002275 BOC Not. on the LEC Networks 1994
Issue ApilI 1994 Signaling
6.5.3 GeneratIon of Delay-Dial Signals
In some switching systems the delay-dial signal is generated in the individual incoming
trunk circuits Such signals are suitable for use with switching systems that either expect
delay-dial without integrity check or delay-dial with integrity check This operation is known as hardware generation of the delay-dial signal
In other equipment such as the 1/lA ESS HILO 4ESS 5ESS DMS-lO and DMS-100F
switching systems the delay-dial signal is generated by the common-control equipment
associated with the trunk equipment This operation is known as software generation of
the of the the delay-dial signal This method permits return delay-dial signal as long as seconds after the connect seizure signal In Figure 6-13 the infonnation for the
1/lA ESS HILO switching system indicates that the delay-dial signal will be returned in
less than seconds This means that software generation of the delay-dial signal is completely compatible only with switching systems that expect delay-dial with signaling
integrity check
START-DIAL SIGNAL
SEIZURE SEEN START END READY TO OF OF RECEIVE SIGNAL SIGNAL DIGITS
Minimum Typicar Heavy Traffic Maximum
C-
Hardware Delay Dial
Loop Slnallng 280 45 10 350 50 10 500 75 15 l6sec 100
EM 330 45 10 400 50 10 550 75 15 l6sec 100
HILO Delay-Dial
Loop and EM 15 280 45 75 350 50 150 500 75 .c5sec 100
Loop 110 140 45 200 155 50 300 175 75 l6sec 200 100
EM 160 140 45 250 155 50 350 175 75 l6sec 200 100
limes In milliseconds unless noted
Figure 6-13 Controlled-Outpulsing Formats for 1/lA ESS System
6-51 BOC Not. on the LEC Networks 1994 SR-TSV-002275 1994 Signaling Issue April
6.5.4 Wink-Start
With wink-start operation the trunk equipment signals on-hook at each end when in the for idle condition On receipt of connect signal the called office initiates request
off-hook to the register but does not immediately return an delay-dial signal calling
is attached office The on-hook signal to the calling office is maintained until the register The wink- at the called office at which time the called office sends wink-start signal
the start signal must meet following requirements
The off-hook must be 140 to 290 ms long
The off-hook to on-hook transition start-dial must not occur until 210 ins after the
connect signal is received
the on-hook transition It is desirable to minimize post-di2ling delay by sending as soon as
The nominal wink-start is 150 possible after the above requirements are met signal ms for the 1/lA ESS 250 ins for 4ESS 220 ins for the 5ESS and 180 ins for the EWSD
is about for and 10 to switching systems It 200 ins DMS-l0 switching systems The 2550 ins in 10-ms steps 150-ms default value for DMS-100F systems Galaxy
System terminal equipment sends 140 ins minimumand 200 ins nominal wink-start
signal The 1/lA ESS switching system delays returning the wink-start signal for slightly more than 100 ms This is the minimum time required to attach register/receiver to the incoming trunk after the connect signal is received The 4ESS switching system usually of the The returns the wink-start signal within few msof the receipt connect signal of the of the DMS-10 system usually returns the wink-start signal within 60 ms receipt connect signal The DMS-100F system returns the wink-start signal 10 to 2550 ma the 100 ma after the receipt of the connect signal In DMS-100F systems in The transitions length of the wink-start signal is adjustable per office 10-ms steps from on- to off- to on-hook with the duration of off-hook constrained as indicated
constitute the wink
The signal transmission system will generally distort the wink As result the calling
office must recognize an off-hook signal in the range of 100 to 350 ins as wink-start be treated wink-start signal Off-hook signals exceeding 350 ins can as glare on 2-way
trunks Section 6.5.5 All wink-start trunks operate in the same manner whether using
EM or loop reverse-battery signaling
The 210-ms minimumdelay between reception of the connect signal and completion of
the wink-start signal is inherent to the operation of the 1/lA ESS switching system
Additional details concerning this subject are provided in Section 6.5.2
of the connect and Wink-start operation requires 210-ms delay between reception signal the completion of the wink-start signal This timing ensures that there is at least 100 ms ESS of off-hook wink signal at time that the signal can be recognized by 1/lA also wink-start to off-hook as soon as switching systems The timing permits signals go
the trunk is seized as is the case with 4ESS and 5ESS systems These requirements are
compatible with all known network arrangements There is however another set of requirements for wink-start that are used for Direct Inward Dialing DID and terminal
equipment as follows
6-52 SR-TSV-002275 SOC Notes on the LEC Networks 1994
Issue April 1994 SIgnaling
ANSI Ti .405-1989 Inteiface Between Carriers and CustomerInstallations
Analog Voicegrade Switched Access Using Loop Reverse-Balterj Signaling6
EIAFIA-464-A-1989 Private Branch Exchange PBX Switching Equipmentfor Voiceband Application and inclusion of EJA 464-1
These requirements would not be compatible with the 4ESS or 5ESS switching systems as this standard changes the requirements for wink-start as follows
For trunks from wink-start in this section the off-hook to on-hook transition
start-dial must not occur until 210 ms after the connect signal is received
For DID from references listed above the on-hook to off-hook transition of the
wink-start signal must not occur until 100 ms after the connect signal
It has not previously been feasible to write single requirement for wink-start With the disappearance of the No crossbar as switching system for private line use it should be possible to have single requirement for all uses of wink-start In the meantime it would be advisable to have terminal equipment able to work with wink-start signal of either type
The capability of various switching systems to expect or send wink-start is covered in
Table 6-12 In the case of expect wink-start ATT and Northern Telecom switching systems time the received off-hook signal On 2-way trunks wink-start signal longer than predetermined length of time is interpreted as glare condition and initiates the start of glare sequence
The list below covers these times for the different switching systems On 1-way trunks wink-start signal longer than predetermined length of time causes the following maintenance activity
1/lA ESS 500- to 600-ms or longer wink-start signal causes the call to be routed
to reorder and maintenance activity started
5ESS switching system 350-ms or longer wink-start signal causes retrial of the
call on first failure and routes the call to reorder on the second failure
DMS-l0 system 400-ms or longer wink-start signal is interpreted as reverse
off-hook make-busy and another trunk is selected to route the call If on the second
trial 400-ms or longer wink-start signal is encountered the call is routed to reorder
DMS-l00 system Allows selectable timing from 10 to 2550 ma in 10-ms steps with default of 350 ins
EWSD system Wink-start signals longer than 420 ma for nonequal-access trunks 752 ins for interLATA carrier trunks and 1500 ins for International Carrier INC
trunks cause the call to be routed to another trunk and maintenance activity started
send wink-start All present CAMA systems
6.53 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling Issue April 1994
The delay introduced by various switching systems from receipt of seizure connect
wink-start is shown in Table 6-14 and signal to the return of delay-dial or signal Figure 6-13
Table 6-13 Delay from Connect to Delay-Dial
Delay in Milliseconds from
Connect Signal to
Delay-Dial
Switching System Wink Hardware Software
1/1AESS SeeFigure6-13
1/1AESSHILO SeeFigure6-13
2/2B ESS 50 to 450 10 to 30 NA 4ESS 50 NA 50
5ESS system 100 to 200 NA 10 to 60 DMS-10 50mm NA 50mm DMS-100F 100 NA 1005 EWSD 56 NA 56
LSSGR No requirement
NA Not applicable
from 2550 office in 10-ms Default value adjustable 10 to ms per steps
6.5.6 Glare
simultaneous seizures both ends because of Two-way trunks are subject to occasional at the the end and the the unguarded interval between seizure of trunk at one consequent making busy of the trunk at the other end giving glare These simultaneous seizures cause each end of the trunk to receive sustained off-hook signal
Equipment at each end should be arranged to
prevent the off-hook signal from reaching the charging control equipment
disengage from this mutually blocking condition
Dependent upon the switching systems involved various techniques are used to reduce ineffective attempts and long time-out intervals due to glare The 1/lA ESS 2/2B ESS
4ESS 5ESS DMS-10 and DMS-100F switching systems use method to detect and resolve glare on both wink-start and delay-dial controlled-outpulsing conditions that
saves both originating calls
64 SR-TSV-002275 BOC Notes on the LEC Networks 1994
issue AprIl 1994 Signaling
6.5.6.1 Glare Resolution in Electronic Switching Offices
Electronic switching systems detect glare by timing the incoming wink-start or delay-dial
signal Where the maximum time for the appropriate controiled-outpulsing signal is
exceeded glare is assumed The office detecting the glare condition holds the off-hook
toward the other office until it can back out of the connection attach register to the
connection and go on-hook toward the other office as start-dial signal The call
incoming to the office detecting glare will be completed on the original trunk The call
outgoing from the office detecting glare will be retried on another trunk Thus both calls
are saved
Any wink-start signal over 350 ma can be treated as glare The actual glare detection times for the various switching equipment are as follows
1/lA ESS switching system 500 to 600 ma
2/2B ESS switching system 450 to 550 ma
4ESS switching system 350 to 500 ma
5ESS switching system 400 to 500 ma
DMS-10 switching system 400 to 500 ma
DMS-100F switching system 350 ma software adjustable 10 to 2550 ma per office in 10-ms steps
EWSD switching system 420 ma for nonequal-access trunks 752 ma for interLATA carrier trunks and 1500 ma for INC thinks
Galaxy System terminal equipment 350 ma
NEAX-61E switching system 350 ma
LSSGR specifies 350 ma
Delay-dial to start-dial intervals that exceed seconds may be considered glare The
1/lA ESS switching system normally has 6-second timing The actual glare detection times when expecting delay-dial for various switching equipment are as follows
1/lA ESS switching system 40.1 seconds with to seconds overall timing optional 0.1 seconds with 16 to 20 seconds overall timing normally used
2/2B ESS system Glare resolution with wink-start only
4ESS system 40.1 seconds intertandem 50.1 seconds tandem connecting
10 seconds second trial intertandem and tandem connecting
5ESS system to 4.2 seconds first trial 10 to 10.2 seconds second trial
DMS-10 system to 50 seconds software-adjustable in 128-ma steps per trunk
group
DMS-100F system 160 ma to 40 seconds software-adjustable per office with
seconds as default value
6-55 BOC Notes on the LEC Networks 1994 SR-TSV..002275 issue 1994 Signaling April
EWSD system 4.0 seconds
Galaxy System terminal equipment seconds
NEAX-61E system to seconds each first and second trials
The LSSGR specifies seconds
In all systems failure on retried call will route the call to reorder
method trunks Wink-start sent is the preferred controlled-outpulsing on 2-way See Table 6-12 Wink-start permits less expensive trunk circuits in electronic switching detection of systems when hardware is used to generate the delay-dial signal and quicker glare for either hardware- or software-generated delay-dial The following protocols are used
IntraLATA The lower-ranked office for example end office should back out give
up control of glare situations in favor of the higher-ranked office for example call that has tandem thereby allowing the greatest chance of completion to
traversed the network and is completing rather than one that is just starting If the
offices are of equal rank the offices are often given control in accordance with their CLLITh alphabetical order in the code listings
InterLATA The office that backs out and the office that remains on the connection
of the and the in the case of glare are chosen by agreement BOC Interexchange Carrier IC
6.5.6.2 Trunk Hunting Method to Minimize Glare
seizures trunk unit The strategy of selecting idle trunks as well as the number of per per
of time has an effect on glare Opposite-order trunk hunting gives lowest glare In this method one office selects from low- to high-numbered trunks while the other office
selects from high- to low-numbered trunks In this selection method glare is possible only when all but one trunk in the group is busy The greater the number of seizures per trunk per unit of time the greater the glare problem When glare is an issue consideration should be given to adding more trunks to the group or to replacing single group of 2-way trunks with two groups of 1-way trunks
of COMMON LANGUAGE is registered trademark and CLE CLLI CLCI and CLFI are trademarks Beilcore
Characteristically between two offices and the office will use the reverse hunting feature The
and office designations should be determined by CLU codes
66 SR-TSV-002215 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
6.5.7 Start-Dial Start-Pulsing
Start-dial is an on-hook signal from the called office to the calling office It occurs when
the receiving office is ready to accept digits However momentary delay of
minimum of 70 ms after receipt of the start-dial signal should be introduced before dial pulsing is started This delay is necessary because dial pulse receivers are sometimes momentarily disabled at the instant of the sending of the start-dial signal to prevent the registration of false reflected pulse Good practice also suggests that dial-pulse receivers at the called end be disabled for 30 to 70 ms after the start-dial signal is sent
There is no standard delay between the start-dial signal and multifrequency outpulsing
for existing switching systems The delay can be to 200 ms depending on the multifrequency sender used
transient noise the Experimental data indicate that the start-dial signal generates at
sending central office that lasts about 20 ms in electronic offices lhis transient can mask the keypulse KP signal long enough to prevent recognition by the multifrequency receiver thereby causing call failure No ATT- Northern Telecom- or NEC- manufactured switching system will accept multifrequency-pulsed address signal unless it begins with KP and ends with ST The nominal transmitted KP signal is from
90 to 120 ms and the multifrequency receiver will recognize KP signal of 55 ms minimum NEC switches wait for 72 ms after the start-dial signal before transmitting the KP It is good practice to introduce minimum delay of 50 ms between the receipt of the start-dial signal and the beginning of outpulsing Actual delays introduced between the reception of the start-dial signal and the beginning of the KP signal are shown in milliseconds as follows
1/lA ESS switching system 100 to 150
4ESS system 2080 or 200 selectable per trunk group
5ESS system 70
DMS-10 system 70
DMS-100F system 70 default value software adjustable per office 10 to 2550 ms with 10-ms steps
EWSD system 92
NEAX-61E system 72
The LSSGR has the following minimum requirements 50 ms under normal conditions and 200 ms on 2-way trunks without glare control
6.5.8 Unexpected Stop
An unexpected stop is spurious off-hook stop signal detected by the sender before or during outpulsing The detection of an unexpected-stop signal is used as trouble condition However prudent use of this test is required because it is possible for many circuits to produce unexpected-stop signals when there is no trouble To prevent taking
6-57 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue April 1994 Signaling
the ATT-made unnecessary trouble records and falsely sending calls to reorder switching machines use different methods to avoid detecting nonproductive unexpected-stop signals
Tandem switching systems can look for unexpected stops during multifrequency
outpulsing on intertandem circuits However no ATT-made switching system looks
is that after the last dial when for unexpected stops after outpulsing completed is pulse
dial-pulsing or after the ST pulse when multifrequency pulsing
follows Switching systems test for unexpected stops during multifrequency outpulsing as
before and The 1/lA ESS switching system looks for an unexpected stop outpulsing
in an interval between the tens and units digits on intertandem tandem connecting
and local trunks
The 4ESS system looks for an unexpected stop after receipt of the start-dial tandem indication to the completion of the ST pulse on intertandem calls and on
connecting calls before outpulsing starts to the hundreds digit for 10-digit outpulsing and to to the ST pulse on 7-digit outpulsing to the tens digit on 5-digit outpulsing
the units digit on 4-digit outpulsing
of the The 5ESS system looks for an unexpected stop during outpulsing after receipt intertandem trunks tandem start-dial signal to the completion of the ST signal on On the tens completing trunks it looks for unexpected stops until finished sending digit
of the line number and is blind to them thereafter
all The DMS-10 system after receipt of the start-dial signal will ignore unexpected
200 if than 200 ins stops that are less than ms an unexpected stop signal greater
occurs before the end of outpulsing the call will be disconnected
for between the tens and the units The DMS-100F system looks unexpected stops
digits
from the validation The EWSD system looks for unexpected stops during outpulsing
of the start-dial signal to the completion of the ST pulse
The LSSGR has no requirement
for as follows Switching systems test unexpected stops during dial-pulse outpulsing
with allowed looks for an The 5ESS switching system stop-go operation unexpected second The 5ESS without stop after the hundreds digit or any stop system stop-go
operation treats any stop as unexpected
The DMS-10 system after receipt of the start-dial signal ignores all unexpected stops
that are less than 200 ins if an unexpected-stop signal greater than 200 ins occurs
before the end of outpulsing the call is disconnected The DMS-10 system does not
operate stop-go
three The DMS-100F system checks for stop signals after each digit and accepts up to trunk stops per call The number accepted is adjustable per group
648 SA-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 SIgnaling
The LSSGR has no requirement
6.5.9 Dynamic Overload Control
Dynamic Overload Control DOC equipment is available for use in electronic switching
offices and is used to send signals to distant offices requesting that they limit the amount
of traffic sent to the electronic office The DOC signals are sent because of shortage of
real time shortage of receivers or lack of capability to switch calls The DOC
control console at the switching office contains lamps indicating the types of signals
being sent It is also network managements practice to carefully monitor traffic in
expected overload situations for example during Mothers Day
6.6 Dial Pulsing
little the The has been Dial-pulsing requirements have changed over years tendency to
provide longer range more resistance in the loop and more margin for satisfactory pulse
reception with the same pulsing limits In all switching systems loop range and pulsing
limits can be traded for each other without changing the physical equipment
The three standards below cover customer installation equipment requirements for dial pulses and range limits that are satisfactory for all existing switching systems
ANSI Tl.401-1988 Interface Between Carriers and Customer Installations
Analog Voicegrade Switched Access Lines Using Loop-Start and Ground-Start Signaling5
EIAITIA 464-A-1989 Private Branch Exchange PBX Switching Equipmentfor Voiceband Application and inclusion ofEJA 464-1
EIA 470-A-1987 Telephone Instruments with Loop Signaling8
TR-NWF-000506 Signaling Sections 6.1 6.4.2
The LSSGR requires that new switching systems receive pulses at higher and lower pulsing speeds and at longer range with the same number of ringers and with the same percent break at the terminal
6-59 BOC Notes on the LEC Networks 1994 SRTSV002275 Issue April 1994 Signaling
6.6.1 Dial-Pulse Generation
from customers dial Dial pulsing is means of transmitting digital information or Dial electronic pulse generator to the central office equipment pulses are momentary Senders that openings of the 1oop that are detected in the switching equipment accept senders that will dial pulses from interoffice trunks are available as well as dial-pulse outward
of With dial pulsing the numeric value of each digit is represented by the number on- hook intervals in train of pulses The on-hook intervals of each digit are separated by off- short off-hook intervals while the digits themselves are separated by relatively long disconnect since hook intervals The on-hook signals are not interpreted as signals they The are considerably less than the minimum disconnect times given in Section 6.4.3 the off-hook between off-hook interval between digits is distinguished from pulses by
when the off-hook is in the order of timing circuit The end of digit is recognized signal 75 to 210 ma
is at of 10 at Dial-pulse signaling ideally originated pulsing speed approximately pps close to the nominal approximately 61-percent break Pulsing speed is maintained as
ratio is 10 pps as economic considerations warrant The break deliberately changed of away from 50-percent break to compensate for the characteristics pulse-receiving differ and to make the equipment and signal transmission systems which substantially break and make time most advantageous use of circuit conditions occurring during the intervals
be the Figure 6-14 illustrates dial pulsing It shows typical pulse generator which may dial the electronic switch in an electronic dial the cam-operated contact in rotary or
circuit these switches or make contact of pulse-repeating relay in signaling as shown dc circuit number of times to the dialed contacts open and close equal digit being Within the Electronic switches have taken the place of most contacts in new equipment context of this document the words electronic switch are interchangeable with dial
also be on the contact or relay contact The pulse generator may keyer operating of the terms in signaling bits in digital bitstream The figure illustrates some employed describing dial-pulse signaling circuits
640 SR-TSV-002275 BOC Notes on the LEC Networks 1994 iiie Signaling
Customer Cential Station Office Set
Loop Dial- ______Pulse Receiver
0ff-Hook Interdigit Connect lime
Dialing Next Make Idle Digit
Circuit Closed
State Of Pulsing 1j1J1J1J 1J1J1J
Circuit Opened 0I l1 Break Duration Make Duration lime I-l 0.1 Pulse Period
Legend
Pulsing Period Break Duration Make Duration me
Pulsing Speed Pulse Per Second 1000 Pulsing Period ms Percent Break 100 Break Ratio
Figure 6-14 Dial-Pulse Signaling
Dial pulses are measured at contact or switch in normal practice This can be the dial contact or electronic switch In the standard listed below one of the proposed detectors slope detector measures the opens and closures of the dial contact or electronic switch remotely by sensing the abrupt changes in voltage as the contact opens and closes It can also be relay contact or electronic switch in pulse-receiving circuit
Methods and equipment for measuring dial pulses are covered in IEEE Standard 753-
1983 IEEE Standard Functional Methods and Equipmentfor Measuring the Performance of Dial-Pulse DP Address Signaling Systems.9 The standard calls for two different pulse receivers The first is relay detector the second is an electronic detector quasi A-relay method is available to measure the waveforms of dial pulses with test circuit and an oscilloscope will be presented later in this section BOC Notes on the LEC Networks 1994 SR-TSV-002275 issue 1994 Signaling April
6.6.2 Loop and Leak
circuit the In dial-pulse receiver using relay series resistance in the connecting that can flow and pulsing contact with the relay winding reduces the maximum current the rate at which the current increases from zero to maximum The net effect of adding
break at the contact Shunt series resistance is the same as increasing the percent pulsing capacitance and shunt resistance have the opposite effect Instead of ceasing abruptly continues at when the pulsing contact is opened relay winding current flowing steady rate through the shunt resistance and then at an exponentially decreasing rate until the
capacitance is charged to the signaling voltage
simulate the effect of In certain pulsing tests series resistance is added to roughly long known the condition loop in increasing the break ratio The test condition is then as loop combinations of resistance with the amount of resistance usually stated Various defined
and capacitance are often shunted across the test circuit to simulate the tendency of the break ratio The conditions ringers ringing bridges and other equipment to reduce
are known as leak conditions
The various leak conditions are shown in Figure 6-15 and is described as follows
Leak lO20O-C 1-percent resistor is connected in parallel with series resistor combination of 2.l6-i.F 2-percent capacitor and 505O-2 1-percent across line located next to the the pulsing contact This leak is the equivalent of customer leak the wire central office equipped with five C4A ringers and 15000-a on drop
This leak is rough substitute for electronic ringers which comprise primarily
resistance and capacitance in series
This leak Leak resistor of 10200 fl percent parallels the pulsing contact subscriber condition represents line-insulation leak of 10200 on 2-party line affect dial where ringers are connected to ground and do not significantly pulsing
Dl
102K 5.O5KQ O.2Xfl 600 15K fl
Figure 6-15 Leaks for Dial-Pulse Testing
6-62 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue Aprli 1994 Signaling
Leak 2.16-jiF 2-percent capacitor in series with 600-fl 1-percent resistor is
connected in parallel with 10200-fl 1-percent resistor across the pulsing contact
This network simulates dial-pulse transmitter with 10200-fl leak across the loop conductors
resistor Leak Dl 2.16-jiF 2-percent capacitor in series with 600-fl 1-percent is connected across the pulsing contact This network simulates dial-pulse sender
circuits on long ioop trunks
with resistor Leak SF 2.16-jiF 2-percent capacitor in series 600-fl 1-percent
is connected in parallel with 15000-fl 1-percent resistor across the pulsing contact
This leak condition is primarily used with pulsing tests designed to check the
operation of single-frequency signaling system
In purely nonreactive dc circuit the flow of current would correspond exactly to the changing state of the pulsing contact In practice however relay-based circuits do have considerable inductance and capacitance so that the flow of current in the relay winding does not correspond exactly to the instantaneous state of the pulsing contact
Furthermore relays cannot exactly translate change of current in their windings into changes of state of their own contacts The important consideration however is the state of the contact which controls all subsequent activity in the circuit For this reason the terms and definitions in Figure 6-14 refer to states of the pulsing contact and not to current flow or any other feature of the circuit The terms break ratio and percent break always imply the presence of switch or relay contact at the point where the break ratio is specified The terms have no meaning apart from such contact
In most cases the contact of the signaling circuit at which break ratio is specified is accessible for the connection of signaling test set Where it is not accessible an relay as part of the test set is substituted for the regular relay solely for the purpose of providing an accessible contact for testing The relay is specific type representative of relays originally used to terminate dial-pulse signaling circuits Pulsing test requirements are then identified with the test relay not with the relay in the signaling circuit for which it is substituted
6.6.3 Dial-Pulsing Limits
Mechanical dials were typically designed to break ratio of 58 to 64 percent made with under service conditions an objective accuracy of 100.5 pps and operated normal between and 11 pps during any portion of the rundown The objective output for modem dial-pulse senders using EM loop or battery-and-ground pulsing is 100.2 pps with 60.02-percent break The majority of senders in service will outpulse 101 pps within the following limits for percent break
EM pulsing 56.0 to 60.0 Loop pulsing 59.5 to 675
Battery-and-ground 48.5 to 66.0
63 BOC Notes on the LEC Networks 1994 SR-TSV.002275 issue 1994 Signaling April
Many automatic dialers are designed for fixed make and break times rather than for fixed values would then be 61-ms break time and 39-ms speed and percent break The central make time Allowing for tolerances of 10 percent from these central values will time 35.1 to break produce the following time values in milliseconds make 42.9 time 54.9 to 67.1
circuits Percent break requirements for the various signaling trunk and pulse-repeater various circuits differ since the percent break maybe shifted in passing through
dial if Signaling circuits are designed to shift the break ratio of received pulses deliverthose necessary to value better suited to the circuit to which they pulses
of must have In general dial-pulse receivers such as the registers switching systems of the and devices capabilities broader than the requirements pulse generators repeating to provide margin for normal variations in break ratio and pulsing speed However short on-hook that could be mistaken for dial pulses switching systems generate signals before the of the interval and shortly These signals occur start pulsing during interdigital that after the completion of outpulsing As result it is recommended dial-pulse and on-hook receivers ignore on-hook signals shorter than 10 ms accept signals greater than 25 ms
the line to At one time it was common for dial pulses originating from customer be The repeated into trunk to second central office then repeated over trunk to third decrease with each link in the connection percent break of the pulses could increase or receiver in the last office however such placing severe limits on the dial-pulse Today cases have essentially disappeared
6.6.3.1 Pulse Waveform Criteria
of that common in Many manufacturers are reluctant to use the types pulsing tests are intraLATA networks When ANSI Ti .401-1988 Interface Between Carriers and
Customer Installations Analog Voicegrade Switched Access Lines Using Loop-Start and Ground-Start Signaling5 was written new type of testing was devised through the cooperation of manufacturers the telephone industry and Beilcore The requirements were divided as follows
of 11 Network Requirements The network will accept pulses at rate to pulses per
second that have from 58- to 64-percent break with the equivalent of up to five C4A type ringers on the line
Customer Installation Requirements The customer installation requirements use
waveform is to lie within when the pulse waveform criteria The required template circuit circuits are customer installation pulses into test Two test specified The noninductive and an inductive circuit together with their corresponding templates for this dial pulses are required to pass both tests The tests have been simplified presentation
644 SR-TSV-002275 BOC Notes on the LEG Networks 1994
Issue AprIl 1994 SIgnaling
The value of is varied from to 1500 The test circuit is shown in Figure 6-16
during the noninductive test
The noninductive template is shown in Figure 6-17
is the time that the current below 14 mA the break interval of T1 drops during each pulse
is the time that the current increases to 14 mA the make interval T2 during
is the that the current below 14 mA the break interval of the T3 time drops during does not to the last dial in train next pulse T3 apply pulse pulse
The ratio of the break time T2 T1 to the period T3 T1 should be 0.58 to 0.64
inductor substituted for the The inductive test circuit is shown in Figure 6-16 with an
in 6-18 For all values of from resistor Specifications for the inductor are Figure R1
to 1500 the current in the test circuit should be within the template of Figure
of in dial 6-19 during the test In addition to reduce the possibility error detecting
pulses the current in the test set should not enter the shaded area
is the time that the current below 20 mA during the break interval of each T01 drops pufse
6.6.3.2 Maximum Number of Dial-Pulse Repetitions Without Pulse Correction
The discussion in this section is applicable to all loop or battery-and-ground dial pulsing values of 42- including the use of dial pulsing to terminal equipment receiving DID The for receivers to 84-percent break at to 12 pps represent limiting condition pulse
These limits are as applicable for electronic pulse detectors as they are for relay types formulated on the use of 221A relay or its equivalent as pulse detector
Demarcation
Point ______R2 39O 1%for Noninductive Test or inductor with 390Q 5% Internal Resistance Customer
Installation R3 10L11% 1500fl
______
Oscilloscope
Figure 6-16 Test Circuit for Dial-Pulse Templates
645 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling Issue April 1994
53125 125125 ______
120 I-
100 -- .1 .J.
80
cceptabIi 60 RegionS
40
85 .3 2.4 20 8O81 8518
20
80.1 91 .1 125-i
-20
20 40 60 80 100 120
Time After T1ms
Figure 6-17 Dial-Pulse Template for Noninductive Test SR-TSV-002275 BOC Note on the LEC Networks 1994
Issue April 1994 Signaling
Mercury-wetted contacts 75 ms open 501 ms closed continuous pulsing
R1 Adjust to 2100 1270 and iOOQ as specified below Tolerances are 1% except as noted
During each loop closure the current shall rise to within5% of the values listed below
Time from start of Instantaneous Loop Current in mA Closure
ms Ri 2100fl R11270fl R1100
7.0 7.9 8.5 10.6 12.1 14.0 10 14.0 17.2 24.5 15 16.1 20.9 35.0 20 17.3 23.5 45.0 25 18.2 25.5 56.0 30 18.8 27.0 67.0 35 19.1 28.0 76.5 40 19.3 28.7 86.0 45 19.5 29.1 92.0 50 19.6 29.3 96.0
Figure 6-18 Inductor for inductive Dial-Pulse Test Circuit
6-67 BOC Notes on the LEC Networks 1994 SR-TSV.002275 1994 Signaling issue April
120
100---
80
60
Acceptable -S Region 40
230
-J 125 20
100 16
201 501
-20
-40
20 40 60 80 100 120
Time After T01ms
Figure 6-19 Dial-Pulse Template for Inductive Test
6-68 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 Signaling
6.6.3.3 Pulse Links and Converters
trunk may be made up of two or more signaling sections connected in tandem using the sections have same or different types of signaling systems If two adjacent EM signaling arrangements an auxiliary pulse link is usually provided to repeat the signals If the two sections are different converters are provided For example if trunk circuit
is connected to trunk using signaling with EM lead employing loop signaling facility control converter is used to convert loop signaling to EM signaling and vice versa of the Where digital carrier systems are connected back-to-back the signaling paths individual channels are usually connected by use of digital cross-connection system or
tandem channel units Both approaches eliminate the use of extra equipment at the point of connection
6.6.3.4 Maximum Number of Dial-Pulse Repetitions with Pulse Correction
The total objective round-trip signaling delay for terrestrial facilities should not exceed
300 ms In the case of delay-dial without integrity check the 300 ma must also include time for the far-end switching system to return delay-dial Because of the time delay inherent in single-frequency signaling two signaling sections of single-frequency
signaling should not be used in applications where delay is important such as delay-dial without integrity check or stop-go operation
6.6.4 Interdigital Time
The interdigital time is the interval from the end of the last on-hook pulse of one digit train of dial pulses to the beginning of the first on-hook pulse of the next digit train See
Figure 6-14 timer or slow-release relay which ignores the digit pulses but releases between pulse trains is used to condition the receiving equipment for the next digit For customer dialing the interdigital time depends on the user
The interdigital time delivered by sender depends on the availability of the succeeding digit When the next digit is immediately available the sender must control the minimum interdigital interval The requirement for the minimum interval is 300 ms previous recommendation was 700 ma based on outpulsing to step-by-step equipment with its slow response time
1/lA ESS 2/2B ESS 5ESS DMS-10 DMS-100F and EWSD switching systems have always had the ability to transmit 700-ms interdigital interval This feature has been added to the 4ESS switching system The 1/lA ESS system has an office option for an interdigital interval of 600 to 1000 ma The default value is 600 ma The DM5-b system can send 700-ms interdigital interval and with the use of different hardware pack can transmit per trunk group software adjustable interval between 200 to 900 ma
The DMS-100F system has software adjustable interval of 70 to 1000 ma The Galaxy
System terminal equipment has always had the ability to send 700 ma interval
6-69 BOC Note on the LEC Networks 1994 SR-TSV-002275 issue 1994 Signaling AprIl
300 Although senders and registers can recognize interdigital intervals as short as ms senders have not in the past used interdigital intervals of less than 500 ms when outpulsing shorter intervals approaching the 300-ms minimummay be used in the future for this interval An accuracy of percent is considered satisfactory timing
termination of the sender must receive stop-dial signal 65 ms before the interdigital interval to allow time for the sender to recognize the signal and stop outpulsing Thus to
time is 600 the total time return useful stop-dial signal when the interdigital ms requirements itemized below measured from the end of the last pulse of digit-pulse train must not exceed 535 ms
The delay due to transit time before an off-hook is seen at the source of the stop-dial
The reaction time required to generate stop-dial
The delay due to transit time before the stop-dial is seen at the originating end
6.7 Loop Signaling
is series circuit illustrated in 6-14 It The basic loop-signaling circuit as Figure provides one signaling state when opened and second when closed The loop-signaling third apparatus is usually combined with other apparatus in trunk circuit signaling of state is obtained by reversing the direction of the current in the circuit Combinations intended for open/closed and polarity reversal are used for distinguishing signals one direction of signaling for example dial pulses from those intended for the opposite direction for example answering signals Stored Program Control SPC switching carrier systems can connect to loop signaling on physical facilities to analog or digital The methods systems or directly to the bit stream from digital carrier principal loop are described in the following sections
6.7.1 Reverse-Battery Signaling
basic methods and takes its from the Reverse-battery signaling employs the above name the and the toward fact that battery and ground are reversed on tip ring to change signal the calling end from on-hook to off-hook This is the preferred and most widely used
6-20 shows basic of loop-signaling method Figure application reverse-battery signaling For simplicity the interoffice trunk is shown as using wire rather than digital carrier channel In the idle or on-hook condition all current sensors electronic ferrod or relay are unoperated and the switch SW contacts are open Upon seizure of the outgoing trunk by the calling office trunk group selection based on the office code dialed by the calling customer the following will occur
SW1 and SW2 contacts close thereby closing loop to called office and causing the
ferrod to operate
Operation of the ferrod signals off-hook connect indication to called office
6-10 SR-TSV.002275 BOC Notes on the LEC Networks 1994
Issue Apr11 1994 SIgnaling
called Upon completion of pulsing between offices SW3 contacts close and the
customer is alerted When the called customer answers the S2 ferrod is operated
Operation of the S2 ferrod results in operating the relay which reverses the voltage
polarity on the loop to the calling end
off-hook The voltage polarity causes the CS relay to operate sending an answer
signal to the processor in the calling office
Section 6.4.3 to 400 is When the calling party hangs up disconnect timing per 150 ms started After the timing is completed SW1 and SW2 contacts are released in the calling
office This opens the loop to the ferrod in the called office and releases the calling
is started party The calling party is free to place another call The disconnect timing in the called office as soon as the ferrod demagnetizes When the disconnect timing is
completed the following will occur
will release The called If the called party has returned to on-hoolc SW3 contacts
party is free to place another call
disconnect Table 6-8 is started in the If the called party is still off-hook timing per called office On the completion of the timed interval SW3 contacts will open The
called customer will be returned to dial tone if the trunk is seized again from the
calling office during the disconnect timing the disconnect timing is terminated and
returned dial The call would be without the called party is to tone new completed
interference from the previous call
office releases Then the When the called party hangs up the CS relay in the calling following occurs
takes described above If the calling party has also hung up disconnection place as
If the calling party is still off-hoolc disconnect timing per Table 6-8 is started On the
completion of the disconnect timing SW1 and SW2 contacts are opened lhis the ferrod in the called office returns the calling party to dial tone and de-energizes
this time After the disconnect The calling party is free to place new call at timing 150 to 400 ms the SW3 contacts are released which in turn releases the called
party The called party can place new call at this tune
6-71 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling April
______Il
02
-r -c-I
xQ Co
____
Figure 6-20 Reverse-Battery Signaling
6-72 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue Ap1I 1994 Signaling
6.7.2 Battery-and-Ground Signaling
increased The range of loop signaling on wire trunks can be by employing battery-and- ground signaling This is accomplished by pulsing both battery and ground connections at the sending end This doubles the effective voltage available for signaling Reverse- battery is generally for supervisory signals from the called end backward signals be Between digits and at the completion of pulsing bridge supervisory relay may substituted for the pulsing battery-and-ground to detect the backward signals This arrangement is sometimes called battery-and-ground pulsing loop supervision When maximum range is required battery-and-ground pulsing battery-and-ground supervision may be employed Caution should be observed in using battery-and-ground with signaling since in some cases it may result in impulse noise adverse effects on data service Figure 6-21 shows circuit using battery-and-ground pulsing with loop holding
This technique widely used at one time has become rare in the presence of digital carrier facilities It may be found on some DID trunks on wire loop plant
Toward Incoming Calling Trunk Customer Circuit -48
-48
Figure 6-21 Battery-and-Ground Pulsing Loop Supervision
6-73 SOC Notes on the LEC Networks 1994 SR-TSV002275 Issue 1994 Signaling AprIl
6.7.3 Idle CIrcuit Terminations and Trunk Capacitance
the and Idle circuit terminations do not affect signaling on EM trunks because such the leads are not in the dc signaling path Idle circuit terminations as typical transmission value of 2.16 iF in series with 900 fi may therefore be used
effect Idle circuit terminations connected to signaling leads have substantial on called end an signaling In the idle condition the termination toward the presented by unit outgoing trunk circuit or incoming trunk signaling or channel using loop signaling
limit includes all shunt should not exceed 0.5 .F capacitance This capacitance and idle capacitances including transmission capacitors contact-protector capacitors circuit termination capacitors
circuit termination in The total trunk capacitance in the on-hook state including the idle and the on-hook the outgoing loop trunk circuit the cable any transmission repeaters 2000-fl terminating channel unit should not exceed jiF for trunks with specified conductor range or jiF for trunks with 4000-fl specified conductor range
6.8 EM Signaling
switchboards The trunk circuits EM signaling was first used on trunk circuits from carrier were introduced connected to various wire-line signaling circuits Later systems used transmit the lead for these circuits Single-frequency signaling was to EM circuits information to the far end Even with the advent of digital carrier EM trunk
stayed in place because the carrier did not replace the trunk circuit function However the functions of the trunk circuit the when electronic switching systems combined carrier terminal in the use of signaling circuit and the digital single package EM Channel in is most signaling began to wane Common Signaling CCS turn replacing in intraLATA networks the use of trunk signaling systems However EM signaling for modern will continue for some time where trunk groups are not large enough more and multitude of methods Centrex tie lines trunks fromCentrex for private networks
private line applications
Type Type II and Type ifi EM signaling interfaces are essentially the only EM found in arrangements used in intraLATA networks The Type ifi interface will be only offices with older ESS and ESS switching systems These interfaces are covered in
TR-NWT-000506 Signaling Sections 6.1 6.4.2
trunk Most signaling systems other than loop-signaling are separate from the equipment The and functionally are located between the trunk equipment and the line facility EM of the leads signaling systems derive their name from historical designations signaling on the circuit drawings covering these systems Traditionally the EM signaling interface consisted of two leads between the switching trunk equipment and the signaling the equipment the lead that carries signals from the trunk equipment to signaling to the trunk equipment and the lead that carries signals from signaling equipment the lead of the trunk equipment As result signals from office to office leave on
circuit in office and arrive on the lead in office In the same manner signals from
6-74 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue Apiil 1994 Signaling
office leave on the lead and arrive on the lead of office The flow of signals between two offices using EM lead signaling is shown in Figure 6-22
Figure 6-22 EM Lead Control Status
lead for each direction of Historically BM signaling circuits used only one
transmission with common ground return This means that the signaling leads had greater noise influence than if the leads were balanced 2-wire as are transmission circuits While EM signaling circuits operated satisfactorily in electromechanical systems they were not satisfactory for electronic systems that required separation of the switching power supply from the power of other central office equipment As result several new EM interfaces were introduced The traditional Type interface and the newer interfaces are described below
6.8.1 Type Interface
The Type interface Figure 6-23 is the original EM signaling arrangement Signaling from the trunk circuit to the signaling facility is over the lead using nominal -48 for off-hook and local ground for on-hook Signaling in the other direction is over the lead using local ground for off-hook and open for on-hook The trunk circuit sensor on the lead should use nominal 48 and essentially the full voltage should appear on the lead during the on-hook state
The battery supply to the lead for the off-hook state may be applied through current limiter to prevent circuit damage in case the lead is accidentally grounded In any case the voltage should not drop more than with 85 mA in the lead The current limiter for the lead is described in Section 6.8.10 In the on-hook state the potential drop from lead to ground at the trunk circuit should not exceed when an external
50 source is connected to the lead through 1000
6-75 BOC Notes on the L.EC Networks 1994 SR-TSVOO2275 Issue 1994 Signaling AprIl
Circuit Trunk Cfrcuit Signaiing
-48 \P
48
Figure 6-23 Type Interface
6.8.2 Type II Interface
The Type interface Figure 6-24 is 4-wire fully looped but nonsymmetric is means of arrangement Signaling from the trunk circuit to the signaling facility by and SB leads for on-hook and opens and closures across the paired signal battery nominal 48 to the SB off-hook respectively Since the signaling facility supplies lead with for off-hook and for on-hook lead the effect is to signal on the battery open the Signaling in the reverse direction is by means of opens and closures across paired Since the trunk and SG signal ground leads for on-hook and off-hook respectively The circuit grounds the SO lead the effect is to signal on the lead signaling facility the lead current limiter supplies nominal 48 to SB through
The trunk circuit sensor on the lead should be biased with nominal 48 except that the if considerable loss of compatibility with test equipment can be tolerated voltage
in the on-hook the full may be between -48 and -21 In any case state essentially
sensor voltage should be present on the lead
lead in the be biased with voltage in the The sensor on the signaling facility may
is it is desirable that range of 10 to 24 When negative bias or reference used the blocking diode be used to prevent the voltage from appearing on the lead during than on-hook state This is required if the voltage is more negative 24
6-76 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Signaling
Trunk Circuit SgnaIlng Circuit SB SB
$P
-24
SG SG
-48 .AP..t
Ferrod Sensor
Figure 6-24 Type II Interface
6.8.3 Type III Interface
The Type ifi interface Figure 6-25 is compromise partially looped 4-wire EM lead arrangement It is essentially Type interface except that the battery and ground and for signaling on the lead are supplied by the signaling facility over the SB SG leads respectively The lead is identical to the Type lead except that the expected current is significantly lower because of the high-resistance lead detectors used in electronic switching systems to replace relays
The signaling facility supplies its local ground to the SG lead and feeds nominal -48 to the SB lead through current limiter The lead sensor should meet the same characteristics as in the Type II interface except that the blocking diode may be omitted
6.8.4 Type IV Interface
The Type IV interface Figure 6-26 is symmetric 4-wire looped EM lead arrangement Signaling fromthe trunk circuit to the signaling facility is by means of opens and closures across the and SB leads for on-hook and off-hook respectively
Signaling in the reverse direction is identical except that it is across the and SG leads
Since the trunk circuit grounds the SG lead and the signaling facility grounds the SB lead the signaling over both the EM leads is by means of open for on-hook and ground for off-hook The Type interface in trunk circuits is identical to the Type JV interface as are the characteristics for both trunk circuits and signaling facilities
6-77 BOC Not. on the LEC Networks 1994 SR-TSV-002275 Issue Aprli 1994 Signaling
Trunk Circuit Signaling Circuit SB SB
-24
Sc3
11
li
Ferrod Sensor
Figure 6-25 Type III Interface
Trunk Circuit Signaling Circuit SB SB Il
-48
SG SG
-48
Ferrod Sensor Contact Protecon
Figure 6-26 Type IV Interface
6-78 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 Signaling
6.8.5 Type Interface
The Type interface Figure 6-27 is symmetric 2-wire EM lead arrangement that signals in both directions by means of open for on-hook and ground for off-hook from the trunk circuit Signaling to the signaling facility is over the lead signaling in
the reverse direction is over the lead This interface is essentially the unbalanced
version of the Type 1V interface in which local ground is used for off-hook instead of the
ground obtained over the SB or SG lead
The Type interface is widely used outside North America variety of other lead
designations are in use besides EM The known corresponding sets are SZ1 Sa and
SR and SZ2 Sb and SS Type interface is nomenclature used only by the BOCs
At present an upper limit of 50 mA in the or leads is used for new designs With
the possible exception of maximum current the design characteristics covered herein
should provide for complete functional compatibility with other systems
The EM lead sensors are biased with nominal -48 and in the on-hook state
essentially the full voltage appears on the leads The sensor resistance is high enough to
limit the signaling lead currents to 50 mA
Most lead in EM test sets used North America are not fully compatible with either
Type IV or interfaces The use of48 on EM lead sensors will help in the standardizing of future test sets
Trunk Circuit Signaling Circuit
Contact Protection
Figure 6-27 Type Interface
6-79 BOC Notes on the LEC Networks 1994 SR-TSV002275 issue 1994 Signaling April
6.8.6 Signaling State Summary
with to the It should be Table 6-14 summarizes the signaling states respect sending end nominal noted that bridged examination of all leads will show essentially 48 or 21 for the 4ESS switching system on the leads during the on-hook state For off-hook states be leads any voltage between 10 and 52.5 for either on- or may found Table 6-14 indicates the signal sent not what bridged measurement might indicate
Table 6-14 Signal States Sent
Trunk-to-Signaling Circuit Signaling-to-Trunk Circuit
Type Lead On-Hook 0ff-Hook Lead On-Hook Off-Hook
Ground Battery Open Ground
Ground II Open Battery Open
Ground ifi Ground Battery Open
IV Open Ground Open Ground
Open Ground Open Ground
6.8.7 Switching Methods
6.8.7.1 Relay Contacts
The simplest switching means for EM signaling is relay contact Transfer contacts
111 contact life and are required for sending on the Type and leads To lengthen
is desirable reduce current surges break-before-make transfer should be used and to maximum of transfer time keep the open interval during transfer to or ms longer may introduce distortion increase in percent break to dial pulsing with certain signaling facilities
6.8.7.2 Solid-State Switches
with the of To maintain signaling compatibility and intemperate probable variety EM characteristics need to be considered lead test equipment the following
Type Lead In the on-hook state the potential drop from lead to local ground should not exceed when 50 are connected externally through 1000 to the lead
8O SR-TSV-002275 BOC Notes on the L.EC Networks 1994
Issue AprIl 1994 SIgnaling
Type Lead if the switch is polarized reversing means should be provided In the
off-hook state the potential drop from the lead to SB lead should not exceed with
50 mA in the lead The current in the SB lead should equal the lead current 10
percent Any difference between the two lead currents implies incomplete separation of condition the intent of the signaling and trunk circuit power systems contrary to Type
II interface arrangement Unless opto-isolators or equivalent are used it appears that
perfect separation cannot be achieved hence the 10 percent allowance given above In
the on-hook state little leakage is permitted If the lead is grounded the lead
current should not exceed 100 pA whether the SB lead is open or connected to 50 If
grounded source of 12 is connected to the lead while the SB lead is open the lead current should not exceed 24 pA
switch should when connected The operate properly to signaling facility applying
nominal 12 or 42.5 to 52.5 on the SB lead The switch should be reversible if it is
polarized since sometimes the battery may be supplied on the lead instead of the SB lead Normal lead current is well under 50 mA but the lead may be grounded
accidentally Three types of current limiter are in use on the SB leads leading to three
fault current characteristics Most commonly resistor will limit the current to steady
maximum of 175 mA Another limiter Positive Temperature Coefficient FTC
thermistor will permit maximum current of 1.7 which drops 75 percent within
about 0.5 second and stabilizes at about 30 mA The third limiter 13 resistance lamp or equivalent will permit apeakof3 to4 which will drop to 0.8 within
10 ms and stabilize at maximum of about 360 mA within 50 ma
Additional details concerning fault currents are provided in Section 6.8.10
Type III Lead The requirements will be similar to those for the Type II lead
switch except 12 will not be found on the SB lead and the leakage requirements for
the on-hook state will not apply When 50 are connected externally through 1000
the lead the potential drop between the and SG leads should not exceed in the
on-hook state
Type IV Lead The Type 1V and 11 interfaces appear identical in trunk circuits when
relay contacts are used The difference is in the signaling facility in that it supplies
battery to the SB lead for Type II operation or ground for Type IV operation The lead
signaling formats are battery and open for Type II and ground and open for Type The
significance of switch leakage in the on-hook states is different For Type II the
requirements given are for effective switch leakage to battery or ground to be at least
500 kfl For Type IV operation only the leakage to ground may be as low as 100 k.Q in the on-hook state Also there are no expected fault currents for the Type IV lead
Therefore if trunk circuit is to be used exclusively for Type IV the switch requirements are relaxed if the trunk circuit may be used optionally for either Type II or
the switch should be designed to the Type II arrangements
6-81 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling April
Type Lead The characteristics of the Type switch are the same as those for the the lead current should Type IV switch with additional provisional consideration that be no greater than 50 mA
Type Lead The Type lead switch should supply local ground to the lead in the off-hook state which should not exceed potential drop across the switch when the
will be between lead current is 250 mA The potential supplied to the switch 42.5 and 52.5 in the on-hook state In the off-hook state the lead current is commonly about 50 mA therehasbeen no limit on the currentand itmay be as high as 25OrnA
The effective resistance of the switch in the on-hook state should be at least 100 ks
The II lead switch should closure across the and SG Type II Lead Type supply should exceed with leads for off-hook The potential drop across the switch not
50 mA in the lead In the on-hook state the effective resistance of the switch should be at least 500 kCZ If the switch is polarized reversing means is required The voltage supplied to the switch on the lead is in the range of21 to 52.5 and the SG lead is be the SG and grounded In some trunk configurations the battery may supplied on lead the lead may connect to resistance ground or voltage in the range of 10 to 24
When the SG lead connects to nominal 50 in the connecting circuit it is possible for about 175 fault ground on the lead to cause surge of up to 1.7 falling to mA after the fault within second and stabilizing at about 30 mA many seconds or may cause steady current of up to 175 mA Normal lead currents are well under 50 mA
characteristics the ifi lead are the as those Type III Lead The of Type switch same for the Type switch except that the maximum current should not exceed 50 mA The
limit is 50 instead of 250 2-V potential drop at mA mA
Type IV Lead Since the Type IV arrangement is symmetric the characteristics of the lead switch are identical to those of the Type IV lead switch
Type Lead Since the Type arrangement is symmetrical switching is the same forboththeEleadandtheMlead SeetheMleadforTypeVabove
6.8.8 Transient Suppression
Under certain circumstances surge or transient suppression circuitry is required
6.8.8.1 Type and Ill Leads
for and Although it appears abnormal past design placed the surge suppression Type 1000-Q Type ifi leads in the trunk circuit In early circuits this was done by wiring
resistor from the lead to ground in the trunk circuit High-wattage resistors were in required since they dissipate about 2.5 in the off-hook state Later zener diode
series with 1000-a 0.5-W resistor was used as general replacement for the higher
6-82 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
power resistor However the resistor may be omitted The present requirement is that the trunk circuit should include 65-V 10 percent zener diode between the lead and ground with the anode connected to the lead The diode should be able to dissipate at least 500 mW
6.8.8.2 All Leads
the should In all interface types if the lead sensor is inductive sensor be equipped with
transient suppressor The requirements for it are that when the lead changes from off-hook to on-hook the voltage rise should not exceed 300 and the rate of rise should
exceed for than 10 not exceed per p.s The voltage surge should not 80 more ms
For nonnal relays with at least 500-C windings network consisting of 470 in series with 0.13 pF will be satisfactory
It is permissible for the signaling facility also to provide network consisting of 470 in series with 0.13 pP across its lead switch Accordingly the design of theE lead sensor should tolerate this capacitance plus its own capacitance and that of the lead
6.8.8.3 Type II IV and Leads
be If the lead sensor except the Type and ifi interfaces is inductive it should provided with transient suppressor meeting the E-lead requirements above
In Type II and IV interfaces it is not permissible to also provide capacitor-type transient suppressor across the lead switch in the trunk circuit if the trunk sends dial pulses or other pulses with timing requirements equivalent to those of dial pulses If the switch requires greater protection than that given by the signaling facilities it must be by means other than capacitor network
6.8.9 EM Lead Current Limits
No lower limit is set for off-hook currents in or leads From practical standpoint the lowest usable currents are approximately or mA If sensor resistance is higher the resistance-capacitance thne constant will cause excessive pulse distortion Since there is no lower limit for currents it is not permissible to use current sensors in any or lead except for the one at the end of the lead
In the past no upper limit was established forE or lead currents The maximum known lead current to signaling facilities is approximately 85 mA into E-type single- frequency units with the next highest being about 55 mA into duplex DX signaling circuits See Section 6.8.10 for lead fault currents The highest known lead current was into No crossbar circuits where it could reach 250 mA or slightly over Most electromechanical systems used relays with currents in the 50-mA range Electronic systems usually draw much lower currents It is desirable that all EM lead currents be liinite.d to maximum of 50 mA in new circuit designs for normal circuit operation
6-83 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling issue April 1994
6.8.10 Current Limiters
Forall Eleads andType IV and VMleads the currentlimits are established by the supply voltage and the sensor resistance In the case of Type II and III leads the current limiting is done at both ends of the leads Having to supply battery to signaling lead is major defect in these three interfaces The following sections discuss limiters in the battery feed to or SB leads
6.8.10.1 Type Lead
The trunk circuit signals off-hook by supplying nominal 48 to the lead In the earlier EM lead circuits resistance lamp was provided in the battery feed to the lead switch These iamps are satisfactory in most respects and are still used resistance lamp used as current limiter in the battery supply of the Type lead represents less than 10 fi cold
To avoid using resistance lamps several circuit designs have been introduced One design uses one fuse per lead Some circuits have used PTC thermistors Another circuit uses 1000-fl resistor If thermistors or resistors are used the resulting circuit should meet the Type interface characteristics
The desired characteristic for Type lead current limiters is that the potential drop in the trunk circuit should not exceed at 85 mA of lead current plus any internal current
6.8.10.2 Type II SB Lead
The signaling circuit with the Type II interface supplies battery usually -48 to the SB lead As in the Type interface current limiter is necessary in this battery feed Three types of limiters are used lamps PTC thrmistors and fixed resistors The known fixed resistor limiters are in the range of nominal 316 to 1000 fi The worst-case fault current is steady 175 mA To maintain maximum compatibility the resistor should not exceed
1000 fi or 500 fi if the circuit may optionally provide Type ifi interface Resistors be under 316 fi may be used but must be large power types The resistor should never under 150 fl
Aresistancelampwitharatingof28 169 mA is usedin one DXcircuit to limit the SB lead current ground fault on the SB or lead can cause current peak of to
which drops to 800 mA within 10 ms and stabilizes at about 360 mA within 50 ms
The third limiter is PTC thermistor used in the G-type single-frequency signaling units
The cold resistance range is 4.0 to 90 fi at 25C Until the thermistor reaches about
50C it exhibits small negative temperature coefficient Thereafter the coefficient becomes positive at and above the switching or Curie temperature The initial fault current will be about 1.6 which may rise slightly for approximately 100 ma and then decay to few hundred mA within 0.5 to second Eventually the current will stabilize
6-84 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Signaling
resistance under 50 mA if there is little or no series resistance to the ground fault Series limits the peak current and slows the decay after the device switches
6.8.10.3 Type Ill SB Lead
there The same current limiters are used for Type ifi SB leads as for Type II except that
circuits and the are three circuits known to use the resistance lamp two DX EM
for the II interface applique All the problems and characteristics are the same as Type limiter should not exceed 500 except that during normal service the resistance of the both furnishes the lead and if the signaling circuit or signaling interface converter SB lead detects the lead signal Where the SB lead is furnished by one circuit and the
detector is in another circuit as is the case in Type Ill-to-Type conversion
limiter for the lead not cause of Figure 6-28 the current SB must voltage drop more than with 85 mA flowing Many trunk circuits with the Type ifi interface use 975- the resultant surge-suppression resistors from the lead to the SO lead voltage
value that test divider effect will reduce the lead voltage to such low some common
sets cannot detect the off-hook state if over 500 is used in the SB lead
Trunk Circuit EM Applique Signaling Circuit
SG
RG
-48
Type ill Type
Figure 6-28 Type Ill-to-Type Conversion Normal Range
6.8.11 CompatIbility
standard lead When trunk and signaling circuits conform to the characteristics for EM between interfaces there will be completely functional dc signaling compatibility any for trunk circuit and any signaling circuit of the same interface type Except any options
645 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling April
is for this assured to provide the particular interface type no other option required compatibility
The characteristics for the Type interface also ensure compatibility with all known
and indicators The absence of for on-hook EM lead testing equipment status ground The makes the Type II lead incompatible with several status indicators and test sets circuit resistance low voltage for off-hook on Type ifi leads when the trunk uses surge The of suppression causes incompatibility with some indicators and test equipment use other than nominal 48 for SB leads or sensors on leads may lead to moderate or where the interface even complete incompatibility with test facilities Therefore even for characteristics permit using other than 48 there should be sound technical reason doing so
6.8.12 Interface Conversion
older facilities the interface with trunk It is possible to use signaling having only Type of circuits having the Type II or ifi interface This connection requires the use
for II conversion circuit the EM applique This circuit has options converting Type or
6-28 is for Type Ill to Type Figures 6-28 and 6-29 show these conversions Figure circuit has normal-range resistance limits For greater range more involved applique the the M-lead toward the been used in which an M-lead relay repeats signal on signaling circuit
6.8.13 Back-to-Back Connections
Sometimes it is desirable to connect trunk circuit of one switching system to trunk circuit of another system in the same building Built-up trunks sometimes make use of These back-to-back signaling facilities interconnected within the same building connections can sometimes be made directly otherwise they are made through auxiliary link circuits depending upon the interface type
Circuits with Type or III interfaces must use an auxiliary link for back-to-back connections as shown in Figure 6-30 Type interfaces can be connected back-to-back
circuit which the conditions of the through an auxiliary pulse-link interchanges signaling and leads Circuits with Type II 1V or interfaces may be interconnected
leads and of to leads and metallically by connecting SB SO one SG SB respectively of the other The SB and SO leads are omitted for Type Back-to- back connections are shown in Figure 6-31 The back-to-back interconnection shown in
Figure 6-31 is used in the 1/lA ESS switching system For earlier systems two lead lead labeled becomes and becomes designators are reversed the SB SB
When two like circuits with Type II interfaces are connected back to back they form symmetric arrangement When signaling circuits are interconnected battery and open are used for the signaling states in both directions Circuits with Type interfaces are connected back to back by simply wiring the lead of one to the lead of the other and vice versa
6-86 SRTSV-002275 BOC Notes on the LEC Network 1994
Issue Apr11 1994 Signaling
Trunk Circuit Circuit EM Applique Slgnailng
MJi
R31 8j Type
Type II
Figure 6-29 Type Il-to-Type Conversion
TrunkClrcuit Audliasy Trunk Unk Repeater
SB
Trunk Circuit
SG SG
-48
Type II LC WE I.lE fl____ Contact Protection ______II JL 1UT Typel
Figure 6-30 Trunk Circuit to Trunk Circuit via Auxiliary Trunk Link Repeater
6-87 BOC Notes on the LEC Networks 1994 SR-TSV002275
Signaling Issu April 1994
Trunk Circuit TrunkClrcult
SB
MSB
SG Ii
Figure 6-31 Trunk Circuits Back-to-Back Type ii
Where trunk circuits are interconnected ground and open are used for the signaling states in both directions Most EM lead test facilities are made for the usual asymmetric interfaces therefore improvisation is necessary to do some of the testing If this is considered to be serious problem the trunk circuits may be interconnected by using an auxiliary circuit
6.8.14 60-Hz Immunity Requirements
EM leads should remain within building or at most pass between adjacent buildings with common ground system They are therefore not exposed to significant 60-Hz induction or lightning and have no requirements in this regard
6.8.15 Working Range
The sensors on the EM leads should be sensitive enough to permit each conductor including SB and SO leads to have resistance of at least 150 fl This means at least
300 on loop basis where applicable The sensitivity should be low enough that 50 or ground through 20000 fl bridged onto either or leads respectively will not be seen as an off-hook state The sensor on the Type ifi lead should accommodate
900-2 surge-suppression resistor from the lead to the SG lead in the trunk circuit
6-88 SR.TSV-002275 BOC Notes on the LEC Networke 1994
Issue April 1994 Signaling
6.8.16 Lead Designations
For Type ifi and IV interfaces the lead signals from the trunk circuit the lead and signals to the trunk circuit and the SB lead supplies battery Types II III or ground
Type IV to the trunk circuit for signaling on the lead The SG lead provides ground to the trunk circuit for signaling on the Type ifi lead or ground-to-signaling circuit for
II and sets of leads are signaling on the lead Types IV When multiple signaling used it is permissible to add appropriate suffixes to identify the sets
The use of EA EB MA and MB instead of SG and SB respectively was started on some circuits mostly for the 4ESS switching system or connecting circuits Before and be the first cutover it was agreed that only SG SB designations would used However there are circuits that continue to use EA EB MA and MB designations
6.8.17 Relative Merits
6.8.17.1 Type interface
In the Type interface battery is supplied at the trunk circuit for both the EM leads In offices This causes high return current through the office grounding system some where the trunk circuits are on one floor and the signaling facilities are on another floor special eqnali7ing jumpers have to be added between the ground systems of the two floors with floors to maintain the required 0.5-V maximum potential between the two large numbers of EM leads in use More importantly it violates the integrity of the office grounding scheme
6.8.17.2 Type II interface
The Type interface provides nearly complete or complete separation between switching and signaling power systems It is least likely along with Type 1V to cause interference to other circuits in sensitive environments Metallic back-to-back interconnection of like circuits is possible
On the negative side when trunk circuit connects to signaling facility having only the
Type or interface the interface conversion circuit adds to the installed cost of the trunk
6.8.17.3 Type Ill Interface
The Type 111 interface is used in 1/lA ESS and 2/2B ESS switching systems It provides complete separation of power systems for the lead and allows the trunk circuit to establish the level of lead current The conversion to Type is cheaper than from Type
to Type
6-89 SOC Not on the LEC Networks 1994 SR-TSV-002275 Signaling Issue AprIl 1994
Drawbacks to the Type ifi interface are its inability to use simple back-to-back interconnection of like circuits and the fact that it does not return the current from the lead to the trunk circuit
6.8.17.4 Type IV Interface
The Type 1V interface has all the advantages of the Type II interface and in addition has
is no battery feed problem It is the ideal EM lead interface where single-lead signaling considered hazard or where separation of power systems is required
6.8.17.5 Type Interface
The Type interface has no battery feed problem although it does not provide separation of power systems there tends to be no return ground current between power systems when the circuit is on- or off-hook in both directions It is the standard outside of North America
6.8.18 EM Lead Connection to Testboards
When the signaling leads of any EM interface appear on jacks at testboards only the EMleads appearonjacksfortesting TheEleadisonthetip andtheMlead isonthe ring of the jack
6.8.19 List of Service Trunks
list of service trunks using EM signaling and the various loop-signaling arrangements is shown in Table 6-15
6-90 Addram Address of Type of Celled of Calling Coin Control Function Equipment Loestlon Direction SupervMon Start Party Party Note Ringing Note Other SIgna
OSPSCoin OSPS Remote To OSPS Wink Inband Loop MF MF Inband5 AN Request Signal
Building Reverse-Battery from OSPS Reverse
Some all combined or High-Low Make Rusyf DialO000 DialO00
DedicaledOO Wink MF MF MultiwinkorEill MultiwinkorHiS Wink EM MF MF Inband Inband AN Request Signal from OSPS Reverse MakeBuay Nink MF MFS MultiwinkorHiS MukiwinkorElS OSPSNon-coin OSPS Remote To OSPS Wink loop MF MF None InbandWink Only AN Request Signal
Building Revese-Batteiy or Wink and MFT from OSPS Reverse Some or all combined Dial High-Low HIS Make 000I Busy Wink None EM MF MP inband Wink Only AN Request Signal DialO00 orWinkandMFr fromOSPSReverae Dedicated 00 HIS Make Busy OSPSCoin and Non- OSPS Remote To OSPS Loop Wink MF Inband Inband MF AN Request -a coin Combined Building Reverse-Battery Signal from
Some or all Combined High-Low OSPS Reverse Dial Make 000041 Busy Cl Wink MF MF Multiwink or HIS Multiwink or HIS
EM Wink MF MF Inband Inband AN Request
Signal from OSPS Reverse Wink MF MF Multi wink or HIS Multiwink or HIS Make Busy -4 Combined 6A Announce- Same To None None None None Intercept No or System Loop None Signal to Announcement
Regular Trouble ment System Remote Reverse-Battery System Accompanying and Machine Building High-Low Seimire to indicate Regular Trouble and Machine
Combined Regular Automatic Same or To System Loop Wink MF None None None Reverse and Trouble Machine Intercept Remote Reverse-Battely Make-Busy
Center Building High-Low AIC EM Wink MF None None None Reverse Make-Busy
Legend
MF Multifrequency
Note Coin control consists of two signals coin collect and coin return
Note Ringing the aislorner
Theinbandsignalswillbeprecededbyawink
Special format See Tables 6-32 6-33 6-34 and 6-35 and Section 6.15
Also and when multiwink is userl operator-attached operator-released signals orexpanded-inband signaling BOC Notes on the LEC Networka 1994 SR-TSV002275 IssUe 1994 Signaling April
6.9 Duplex Signaling System
The last link between the Duplex DX signaling is still used to some degree signaling is often DX serving office and PBX or ACD using EM signaling most signaling unless Digital Loop Carrier DLC is used
and dial the of DX signaling was developed to provide dc signaling pulsing beyond range
in that it loop-signaling methods DX signaling is duplex operation is provides semiconductor detector at simultaneous 2-way signaling paths sensitive polar relay or distant end networks are each end of the line receives signals fromthe Balancing the resistance of the line provided and must be adjusted for each circuit according to conductors
circuit that is identical at both DX signaling is based upon balanced and symmetrical circuit the ends Figure 6-32 shows trunk using this method The signaling uses same the current into the of the conductors as the talking path Introducing signaling midpoints the from the repeating coils does not require filter to separate signaling frequencies
voice transmission One conductor in the DX system carries the supervisory and pulsing
from differences in signals Both conductors individually carry currents resulting in the second wire terminal ground potentials and battery supply voltages so that current
can cancel the effect of this unwanted current in the first wire This arrangement gives and and self-compensation against differences in ground potential ac induction partial
compensation for battery supply variations
Figure 6-32 DX Signaling Circuit
6-92 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
With proper balancing network adjustment DX signaling circuits will repeat 12 pps of 58-percent break with distoition not exceeding percent break This performance is
is better than for most loop-signaling arrangements single DX signaling section limited to maximum loop resistance of 5000
leads their Sometimes it is necessary to extend signaling circuit and beyond normal circuits used limitations For this purpose signal lead-extension are to secure adequate circuit with additional range In effect this circuit consists of DX signaling an relay circuit lead This circuit often designated DX2 converts signals from signaling
the function is conditions to signaling circuit lead conditions More usually DX2 built into channel unit for digital carrier system
be balanced for static or dc balance is DX signaling equipment must proper operation
is achieved resistor required as well as transient balance The dc balance by adjusting in the balancing network of the DX1 or DX2 to 1250 plus resistance of the loop
To obtain satisfactory transient balance of the relay use simple balancing network consisting of the line balancing resistance shunted by an experimentally determined capacitance All trunk arrangements can be balanced using iF in the balancing network if pF is used at the repeat coil midpoints of 2-wire line or if tF is used across the simplexes of 4-wire line
the time it takes When change of signaling state is sent over DX signaling facility circuit between and 25 This that signal to arrive at the terminating ranges ms delay
total trunk the coil time is dependent primarily on the capacitance including repeat midpoint capacitor cable capacitance and capacitance of any repeaters in the trunk The conductor resistance is significant only insofar as it represents greater mileage and therefore more cable capacitance The battery voltage and balancing network capacitor are not significant factors
6.10 EM Signaling for Customer Installation Equipment
tie trunks The tie trunks between the and EM signaling is often used on to PBX LEC the customer are terminated at the demarcation point lie trunks can use all the signaling protocols and signaling systems used for interoffice trunks as covered in Section 6.3 through Section 6.13
6.10.1 Protocol Differences Between Customer Installation Signaling and Central Office Signaling
EM signaling at the demarcation point is usually identical to central office trunk signaling That is the signals from the customer are sent on the lead and received on the lead that is the customer originates on the lead
However some EM signaling from the customer uses the lead to send signals and the
lead to receive signals In the language of customer signaling the customer originates on the lead
6-93 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Signaling issue AprIl 1994
6.10.2 EM Lead interfaces at the POT
The customer uses both Type and Type signaling interfaces Originating on the
lead the interfaces look and operate identically with the Type and Type interfaces in
Section 6.8 However when the customer originates on the lead the Type and Type the four II interfaces look and operate quite differently The figures showing customer
premises interfaces are as follows
Type Customer installation originates on the lead Figure 6-33
Type Customer installation originates on the lead Figure 6-34
Type II Customer installation originates on the lead Figure 6-35 6-36 Type II Customer installation originates on the lead Figure
6.10.3 EM Signaling Standards for Customer Installation Equipment
The Type and Type II interfaces and protocols for customer installation that originates on the lead are covered in EIA/TIA 464-A-1989 Private Branch Exchange PBX Switching Equipmentfor Voiceband Application and inclusion of EJA 464-1 ANSI
T1.409-1991 American National Standard for Telecommunications Interface Between
Carriers and Customer Installation Analog Voicegrade Special Access Lines Using
EM Signaling10 covers all four of the interfaces described above
6.11 AC Supervisory and Addressing Systems
The ac signaling systems have been designed to convey the basic trunk supervision and dial-pulsing addressing functions required by switching systems They are used over network trunks where dc signaling is not feasible or economical such as circuits derived from carrier systems Two-state ac signaling can handle trunk supervision and dial pulsing Three-state ac signaling has been designed to handle foreign exchange trunks
Multistate ac signaling in the form of multifrequency pulses is used only for addressing and must be coordinated with two-state signaling systems either ac or dc for supervision DTMF signaling is another multistate system
Inband systems could use frequencies in the voiceband from about 500 Hz to about
2600 Hz requiring signaling equipment only at the terminals of transmission path
Inband signals are of the same order of amplitude as voice currents so as not to overload voice amplifiers or cause crosstalk
644 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl1994 Signaling
POT BOC Customer Demarcabon Network installation
-48V
-48V
Contact protection required If the detector Is Inductive
Figure 6-33 Type Interface Customer Originates on the Lead
BOC POT Customer Network installation
-48V __ II
-48V
Contact protection required If the detector is Inductive
Figure 6-34 Type Interface Customer Originates on the Lead
6-95 BOC Not. on the LEC Networks 1994 SR-TSV.002275 Issue 1994 Signaling AprIl
BOC Customer Netwoik Instailallon
-48V
-48V
Contact protection required If the detector is Inductive
the Figure 6-35 Type II Interface Customer Originates on Lead
POT BOC Customer Network installation
Detector
-48V
is inductive Contact protection required If the detector
Figure 6-36 Type Ii Interface Customer Originates on the Lead
6-96 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April i994 Signaling
facilities At one time there were great many interoffice trunks and foreign exchange using single-frequency signaling Today most of the trunks between SPC switching in wide the of systems use digital carrier with its bitstream signaling With CCS use use digital carrier signaling has begun to disappear
For further information on single-frequency signaling and measurements on single- frequency signaling see IEEE STD 752-1986 IEEE Standard for Functional
Requi rements for Methods and Equipment for Measuring the Performance of Tone
Address Signaling Systems.11 For information on digital carrier see TR-TSY-000510
System Interfaces Section 1012 and PUB 43801 Digital Channel Bank Requirements and Objectives.13
6.11.1 SIngle-Frequency Signaling
One of the chief problems with inband signaling is prevention of mutual interference between voice transmission and signaling Voice-frequency signals are audible and
the time the channel is used for consequently signaling should not take place during conversation Since signal-receiving equipment must remain on the channel during conversation to be ready to respond to incoming signals it may be subject to false operation from voice sounds that resemble the tones used for signaling Protection against voice interference can be accomplished in number of ways
be used Signal tones of character not likely to occur in normal speech may
due Timing for sustained signaling tones may be used to prevent false operation to
voice frequencies occurring in the signaling band
be detected and Voice-frequency energy other than the signaling frequency may
used to prevent false operation of the signaling receiver
the for trunks over Single-frequency signaling systems pass necessaiy signals telephone
without the normal of these facilities for voice-frequency line facilities impairing use speech These systems deliver and accept dc signals to and from the switching trunk equipment in the form of loop or EM lead controls The dc signals are transformed to ac on the line side and vice versa
Single-frequency signaling uses 2600 Hz for signaling on the transmission facility in of both directions Consequently it may be applied to any voice-grade channel any length and makeup provided that it is 4-wire from end to end
The on- and off-hook conditions for basic single-frequency signaling systems are shown in Table 6-16
6-97 BOC Notes on the LEC Networks 1994 SR-TSV002275 Issue 1994 Signaling AprIl
Table 6-16 On- and Oft-Hook Conditions
Signal Tone Direction Lead Condition
On-hook On Sending Ground
Receiving Open
Off-hook Off Sending Battery
Receiving Ground
voice its Since the single-frequency signaling system uses tone on the 4-wire path
different from those of dc The differences are as characteristics are quite systems major follows
have in time Single-frequency signaling systems longer delay signaling
They may distort on-hook or off-hook signals This is particularly true of foreign
exchange units
They have lower pulsing speed and narrower percent break range for incoming dc
pulses Pulse correctors are included to bring the incoming pulses within the percent
break range that the single-frequency signaling can accept
and after transitions between and off-hook They interrupt the voice path during on-
Continuous tones can cause them to malfunction
6.11.2 Signaling Equipment
number of from number of The LECs are presently using signaling systems manufacturers The basic principles of all types are the same The differences are
and the All families primarily in the packaging of the components design technology provide for 2- and 4-wire EM trunk signaling 2-wire loop-trunk signaling and 2- and characteristics 4-wire foreign exchange line signaling either loop- or ground-start The
6-37 is of typical single-frequency signaling units are covered in Table 6-17 Figure unit block diagram illustrating the basic features of an EM four-wire signaling
6-98 SR-TSV-002275 BOC Notes on the LEC NetworksI 994
Issue AprIl 1994 SIgnaling
Table 6-17 Typical Single-Frequency Signaling Characteristics
General
Signaling frequency tone 2600 Hz
Idle-state transmission Cut
Idleibreak Tone
Busy/make No tone
Receiver
Detector bandwidth 50 Hz ati dBm early 30 Hz ati dBm later
Detector sensitivity 24 dBm 31 dBmO
Detector nonoperate 30 dBm 37 dBmO
Detector overload dBm dBmO
Band elimination filter
Insertion loss 45dB
Insertion time 13 ms
Release Time 300 ms
Pulsing rate 7.5 to 12 pps
EM unit
Minimum time for on-hook 33 ms
Minimum no tone for off-hook 55 ms
38 to 85 Input percent break tone 10 pps
Elead Open when idle
unit Originating loop reverse-battery
Minimumtoneforidle 4Oms
Minimum no tone for off-hook 43 ms
Minimum output for on-hook 69 ms
Voltages on transmission leads
48 on ring and ground on tip On-hook
48 on tip and ground on ring Off-hook
6-99 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling AprIl
Table 6-17 Typical Single-Frequency Signaling Characteristics Continued
Receiver contd
Terminating loop reverse-battery unit
Minimumtoneforon-hook 9Oms
Minimum no tone for off-hook 60 ms
Minimum output tone-on 56 ms
Loop open On-hook
Transmitter
Low-level tone 36 dBm 20 dBmO
High-level tone 24 dBm dBmO
High-level tone duration 400 res
Precut ms
Holdover cut 125 ms
Crosscut and on-hook cut 625 ms
EM unit
Voltage on lead Off-hook no tone
Minimum ground on lead 11-21 ms
Minimum voltage on lead 19-2 ms
Minimum output tone 21-51 ms Minimum no tone 1-26 ms
Originating loop reverse-battery unit
Loopcurrenttonotone l9ms
or no loop current to tone
20 Minimum input for tone out ms
Minimum input for no tone out 14 ms
Minimum tone out 51 ms
Minimum no tone out 26 ms
Loop open On-hook
6-100 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issu AprIl 1994 SIgnaling
Table 6-17 Typical Single-Frequency Signaling Characteristics Continued
Terminating loop unit
Reverse-battery to no tone 19 ms
or normal battery to tone
Minimum battery for tone out 20-25 ms
Minimum reverse-battery for no tone 14 ms
Minimum tone out 51 ms
Minimum no tone out 26 ms
Battery on lead 48 on ring and ground on tip On-hook
6.11.2.1 Single-Frequency Transmitter
lead and The keyer relay Figure 6-37 is operated and released by signals on the transmit line of the The the removes or applies 2600 Hz to the facility relay operates
HL relay to remove the 12-dB pad in order to permit high-level initial signal to secure
an improved signal-to-noise operating environment The HL relay is slow to release level In hence dial pulses that operate the relay are transmitted at an augmented
addition cutoff relay operates to block any noise that may be present from the office
side of the circuit
Typical single-frequency signaling units will accept and transmit dial pulses at speeds
from to 12 pps with 56 to 69 percent break lithe range of percent break presented to the lead is outside these limits means must be provided to bring the range within these
limits In general this is done with an lead pulse corrector
Limitations in percent break for loop-type units are overcome by the built-in transmitting pulse corrector
break When using single-frequency signaling without pulse correction the percent range
is limited to sender outpulsing In addition because of the pulse-shaping methods in the
sender most loop dial-pulsing units also require built-in pulse correction
The pulse correction lengthens the short pulses and ensures minimum interpulse
interval typical pulse corrector lengthens any pulse over 17 ms to an output of at least 46 ms In addition the pulse corrector guarantees an interval of at least 23 ms between pulses The distortion from lead to tone in later units is ms
6-101 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling Issue AprIl 1994
BEF Band-Elimination Filter BPF Bandpass Filter
Figure 6-37 EM 4-Wire 2600-Hz SF Signaling System
6.11.2.2 Single-Frequency Receiver
unit band The receiving portions of the single-frequency include voice amplifier elimination networks and signal detector The voice amplifiers primary function is to block any noise or speech present in the office equipment from interfering with operation of the signal detector and also to make up for the insertion loss of the signaling unit in the receive speech path The signal detector circuit includes an amplitude limiter signal- guard network rectifiers dc amplifier and pulse-correcting circuit the output of which operates relay to repeat signals to the lead of the trunk relay equipment
Typical transmission characteristics are shown in Table 6-18
6-102 SR-TSV-002275 BOC Not. on th LEC Networks 1994
Issue April 1994 Signaling
Table 6-18 Typical Transmission Characteristics
Line Receiver
Level Transmission Level Point dB TLP 600
Line Transmit
Level -16dBTLP6002
Overload level -6 dBm -22 dBmO
Equipment Transmit
Maximum TLP 4-wire -f6.5dB600fl
Maximum transmit TLP 2-wire 3dB
Minimum receive TLP 2-wire 12dB
Impedance 2-wire 600/900 fl 2.16 iF
Hybrid loss 2-wire 4.2 dB
Trans-hybrid loss properly terminated 47dB
Equipment Receive
Maximum TLP 4-wire dE 600 fl
Oto 16.5 dB Attenuation dB0.1 steps
Insertion Loss
kHz 2-wire 4.2 dB Ref 4-wire 0.5 dB Ret
kHz transmit cut Ret -4-69 dB
2.6 kHz Band Elimination Filter in Ref-f4OdB
200 Hz 2-wire Ref1 dB 4-wire Ret 0.15 dB
3kHz Ret 0.3dB
Delay Distortion 500 Hz to kHz 180 ps
6-103 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling Issue AprIl 1994
Transmission Level Point The receiver sensitivity is 29 dBm or less at the zero TLP discrimination to The signal-guard network provides the necessary frequency separate the of the signal and non-signal guard voltages By combining voltage outputs signal from and guard detectors in opposing polarity protection against false operation speech and and noise is secured The guard feature efficiency is changed between the dialing talking conditions to secure optimum overall operation
and the and An incoming signal is separated into signal guard components by signal guard detectors The bandwidth of the signal component is approximately 100 Hz
is all other in the voiceband centering on 2600 Hz The guard component frequencies in the These components produce opposing voltages with resultant net voltage signal detector In the talking condition tone off in both directions the guard detector sensitivity requires almost pure 2600-Hz tone to operate the receiver since non-signal frequencies will produce voltage opposing its operation The guard principle is an insufficient important feature in avoiding signaling imitation by speech It is however false of the receiver to ensure that speech-simulated signal will not cause operation talk-off An additional time delay is therefore provided so that during the dialing of 35 for condition the receiver will just operate the RG relay on tone pulse ms E-type units When the RG relay operates it causes slow relay to release greatly channel decreasing the sensitivity of the guard channel and making the signaling responsive to wider band of frequencies This slow release reduces talk-off Early- vintage units can receive dial pulsing only when sending on-hook to the originating end
Later units can receive dial pulsing regardless of supervisory state
6.11.2.3 Voice Path Cuts and 2600-Hz Band Elimination Filter Insertion
Single-frequency signaling units interrupt the transmit voice path to improve signaling margins 2600-Hz Band Elimination Filter BEF is inserted in the receive path whenever the unit receives 2600-Hz tone The filter blocks the tone but permits audible
the without the ring busy and other call progress signals to be heard by calling party from the signaling tone In addition the filter prevents the single-frequency tone entering next signaling link The typical ifiter insertion time is 13 ms The early-vintage units use relay to insert the ifiter They delay inserting the filter for about 100 ma To prevent excessive single-frequency tone from entering the next link the units employ an electronic cut in the voice amplifier in the receive path The cut limits the single- frequency tone leak to maximum of about 30 ma The sequence is to operate the cut insert the filter and restore the receive voice path The cut is controlled to minimize thump The later units use only the filter to limit the duration of the 2600-Hz tone that can enter the next signaling link An electronic switch is used to insert the filter over period of time The gradual insertion nearly eliminates any thump that would be associated with the filter insertion
Cut circuits break and terminate the transmitting voice path when both ends are on-hook for all units and also momentarily after most changes in signaling state The duration of this cut must be considered when tones are sent from the switching equipment after change in signaling state
6-104 SR-TSV-002275 BOC Notes an ths LEC Network 1994 Issue Ap1I 1994 Slgnailng
have identical cut but the is of The various signaling units do not times following typical unit The unit the transmission cut timing in sender dial-pulse or multifrequency pulse when both ends are on-hook when the near has the transmitting path continuously cut
is reestablished in end goes off-hook the transmitting path at the near end nominally
125 ins At the far end the transmitting path is reestablished nominally in 625 ms If
the cut is to the shorter the far end goes off-hook during this interval timing changed interval
the voice is If both ends are off-hook and the near end goes on-hook transmitting path Most units have the transmit cut cut and then reestablished nominally in 625 ins path feature
of the Multifrequency pulsing is not affected by these cuts because the signaling delay the time to attach is in excess of the cut single-frequency system plus required register timing
6.11.2.4 Signaling Delay
consists of the from the The signaling delay through single-frequency system delay the transit time change of state of the dc input to application or removal of signaling tone time of the distant unit of the transmission facility and the response
The transmission delay is the 1-way delay of the transmission facilities between two
network locations This delay applies to either forward or return signal It depends on
the transmission facility types their links and any multiplexing delays Average delays mile of fiber are about 0.4 ms per pair of D4 channel banks 0.C084 ins per route facility which excludes channel banks and 0.082 ins per route mile of voice-frequency facility other For This type of delay is very short compared with system delays an extreme
channel banks and 15 miles at intraLATA case of 600 carrier miles pairs of loop
each end the total transmission delay is about ms The transmission facility delays of
most trunks are much less than this
correction that suitable for With late-vintage EM lead units without built-in pulse are
senderized dial pulsing the nominal delay from off-hook to on-hook is 21 ms from the
time the lead is changed from battery to ground until tone is transmitted plus the
transit time of the facility plus nominal 55 ins for recognition of tone presence and
removal of ground from the lead nominal total of 76 ins plus transit time
between two network The typical 1-way delay times for single-frequency signaling
locations are shown in Table 6-19
6-105 BOC Notes on the LEC Network 1994 SR-TSV-002275 Signaling Issue April 1994
Table 6-19 Typical Single-Frequency Signaling Delays
Seizure Disconnect
EM 76 ms 44-54 ms
Originating to Terminating 79 ins 109 ms
59 Terminating to Originating NA ms
6.11.2.5 Continuous Tones
Continuous tones can interfere with the proper operation of single-frequency signaling It is obvious that pure tone near 2600 Hz will cause the far-end receiving unit to go on- hook It is also true that continuous tones that are not 2600 Hz will act as guard signals and keep the signaling units off-hook even though 2600 Hz is also present Continuous tones can also hold unit on-hook after the signaling tone is removed
Most signaling units have the cut circuits described in this section that permit use with continuous tones However few do not As result provision must be made to interrupt tone sources on periodic basis or when supervisory state is changed The
102 test line see Section for instance would not give accurate results if the test tone and off-hook were applied at the same time because the tone would hold some single- frequency units on-hook and keep the 2600-Hz filter in the circuit For this reason the
off-hook for tone on the 102 test line should be applied 300 ins after the proper operation
6.11.2.6 Foreign Exchange Line Signaling
There are similarities and differences between line and trunk single-frequency signaling that will help in understanding the basic operation and compatibility of line signaling without the detail covered previously for trunk signaling
There are two types of signaling on lines loop-start and ground-start Line signaling is described in Section 6.2 and its associated references
Loop-start is used for ordinary telephone key systems and similar services Ground-start is used for PBX and other services that must have dc signal to indicate when dial tone is applied by the serving switching system or is used to avoid glare
This discussion assumes that the network uses conventional battery supply with battery on line lead usually the ring and ground on the other line lead usually the tip
Floating battery supplies as discussed in Section 6.2.1 are not considered in this discussion although they are generally compatible with the line single-frequency signaling units discussed here
6-106 SR-TSV-002275 BOC Notes on the LEC Network 1994
Issue April 1994 SIgnaling
Single-frequency signaling units used for line signaling have the same general characteristics as those for trunk signaling These similarities are as follows
There is 2- or 4-wire transmissionon the drop sides of the signaling units
There is 4-wire transmission on the line sides of the signaling units
The line transmit is at the16 dBTLP
The line receive is at the dB TLP
identical trunks Supervision and dial pulsing from the station are to loop signaling on
The nominal 2600-Hz tone level is 20 dBmO
Tone-on is on-hook tone-off is off-hook but with exceptions covered below
from The line signaling units do the following differently the trunk units
The loop-start Foreign Exchange Office FXO signaling unit central office end
does not send supervisory signal to the Foreign Exchange Station FXS unit
station end
The ground-start FXO unit removes tone to the FXS whenever the tip is grounded station The ground-start FXS grounds the tip toward the terminal whenever
2600 Hz is absent
unit the to 2600-Hz tone toward the The ground-start FXS converts ground on ring
FXO unit The FXO converts tone from the FXS to ground on the ring
the and from the The ground-start FXO unit recognizes ground on tip no tone FXS as
signal to convert to the loop signaling mode
The ground-start FXS recognizes removal of 2600 Hz from the FXO and closed
loop at the station as signal to convert to the loop signaling mode
The FXO unit receives ringing from the switching system and converts the 20-Hz
2600-Hz With is converted to 2600- signal to tone signal loop-start ringing pure
Hz tone With ground-start ringing is converted to 2600-Hz tone modulated by 20Hz
The FXS converts the tone ringing signal to 20-Hz ringing signal superimposed on
50-V supervisory signal
For ground-start cases only when the central office disconnects first ground is
removed from the tip This causes application of 2600 Hz toward the FXS The FXS does four things
It applies tone toward the FXO
It converts to the ground-start mode
the the It removes ground from tip toward station opening loop current
Removal of tip ground causes the station to release
6-107 SOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling AprIl
the It applies 2600 Hz toward the FXO This returns the FXO to ground-start
mode and removes the loop closure toward the central office
With all these actions complete the circuit returns to the idle condition
When the station disconnects first the station opens the loop to the FXS The FXS
the it the to applies 2600 Hz toward the FXO Tone toward FXO causes to open loop when the central office the central office For the ground-start case only disconnects
is The FXO to the ground removed from the tip to the FXO restores ground-start to the mode and applies 2600 Hz toward the FXS The FXS restores ground-start station mode and removes ground fromthe tip of the line to the station The releases
With all these actions complete the line returns to the idle condition
at the The signaling delays from input at an FXO to the output FXS loop-start single- than in trunk units These of 100 to 500 frequency signaling units are longer delays ms do not affect the basic service from line They may however affect machine- wire line The from an controlled device that operates satisfactorily on signaling delay
is about the with trunk input to an FXS to output at an FXO same as single-frequency unit in dc signaling units In addition the signaling removes changes voltage/current from the network For example Open Switching Intervals OSIs see Section 6.2.3 and the open circuit condition used in many switching systems to release lines on hold are blocked by the signaling units
the There are much longer signaling delays from input at an FXO to the output at FXS
distortion is ground-start units than in trunk signaling units In addition signaling distortion because introduced in these signals from the FXO to the FXS The occurs for the disconnect delay for disconnect signals from the FXO to the FXS is longer signal
remove ground from tip than for seizure signal ground on the tip typical signal from 300 to distortion is 150 ma although individual signaling distortions can go
500 ma The delay and distortion are in both units which reduces the lengths of OSIs
and negates the PBX loop test described in Section 6.2.9
6.11.3 Out-of-Band Signaling Digital Carrier and Digital Switching Systems
The channel units of digital transmission systems have built-in signaling functions and used for the employ out-of-band signaling The eighth bit of time slot normally transmission of speech is used for indicating the on-hook state during signaling sequence This is done in manner analogous to the transmission of 2600-Hz tone bit be used representing the on-hook state for inband signaling The eighth may exclusively for signaling in the obsolete D1A and D1B channel banks or only every
sixth frame in all modern systems The channel units contain the circuitry for
converting between the signal on the digital transmission line and the form of signal In loop EM ground-start etc required by the terminating or switching equipment respect to signaling features D-channel bank units resemble single-frequency signaling units However the signal delay and distortion of the 1-channel banks are far less
Signaling distortion is below ma The signaling range is to 12 pps at 10- to 90-
6-108 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 SignalIng
channel units in channel banks percent break The end-to-end signaling delay for EM is 0.2 ins D1A 0.6 ins D1B 1.6 ins DiD D2 D3 D4 and msD5 When digital switches are connected directly by digital lines there are no channel banks to introduce delay or pulse distortion
Oneof the problems with the signaling associated with 1-channel banks is the accuracy
transmits is that has been with which the system pulses split pulse single pulse cli Vided in two by false off-hook it is usually associated with pulses detected by
detectors also detect pulse-repeating relay However electronic pulse can split pulses
The condition is usually caused by mechanical/electrical oscillations in the circuit Many
have in the These not metallic loop signaling circuits momentary splits pulses are always seen at the far end of the circuit because the characteristics of the wire pair does smooth out these signals However the signaling of the 1-channel bank not provide
the arrive at the far office where it this smoothing and split pulse can can cause wrong numbers or other problems
Digital transmission facilities have 1-way transmission delays as follows
trunks has of about pair of D-channel banks of types used for message delay 0.35 ins
of The T-carrier line has delay 0.0079 ms including repeaters per ml
Fiber line facilities have delay of 0.0084 ms per mi
The 4ESS switching system has delay of ms
The Echo Suppressor Terminal ES1 associated with the 4ESS system has delay of 0.2 ms
The 5ESS system has nominal delay of 0.44 ms Delay is less than 0.56 ma 99
percent of the time
The DMS-10 system has nominal 1-way outgoing and incoming transmission delays
of 0.19 and 0.35 ms respectively
PUB 43801 Digital Channel Bank Requirements and Objectives13 includes the signaling characteristics of channel units These include the following
Sleeve ground Dial-Pulse Originating SDPO channel unit
Dial-Pulse Originating DPO 2-wire channel unit
Dial-Pulse Terminating DVI 2-wire channel unit
EM channel units
Foreign exchange channel unit Station End FXS
Foreign exchange channel unit Office End FXO
Multifrequency Signaling Originating MFO 2-wire channel unit
6-109 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Signaling Issue AprIl 1994
in each direction The Most signaling on trunks requires only single signaling path time-sharing of the least significant speech bit one frame out of six gives 1333 bps path which is highly satisfactory for this purpose For some foreign-exchange circuits two paths are needed toward the distant station for example to alert the station and to
send forward-disconnect signals In this case the shared signaling bit is further
each of 666 2/3 subdivded into and signaling bits at rate bps
be By contrast in DLC systems much more complex set of signaling conditions must provided TR-NWT-000303 Integrated Digital Loop Carrier System Generic
Requirements Objectives and Interface14 defmes the four signaling bits and Termin1 of the for transmission of signaling between the Integrated Digital flT carrier switching system and the Remote Digital Terminal RDT of the system
in the 18th and These ABCD bits are the least significant bit of each channel 6th 12th 24th frames of the 24-frame extended superframe Signaling is accomplished by encoded with replacing the bits located in these positions of the originally byte relate the call of the subscriber line signaling bits The replacement bits typically to state as for example on-hook and off-hook states
The ABCD bits allow maximum of 16 possible states per channel Functionally these
bits comprise per-channel data-links operating at rate of 333.3 bps Signaling
information is refreshed every ms and conveys signaling/supervision information
related to the associated channel
The use of these data-links will depend upon the specific line terminating equipment
Alternate means of conveying equivalent information may be available and thus this 64 form of signaling will not always be used For example in order to provide clear
kbps capability on all DSOs separate signaling channel is required
Table 6-20 gives the ABCD-bit codes for locally switched services from IDT to RDT
Table 6-21 gives the corresponding codes for the RDT-to-JDT direction TR-NWT and 000303 Integrated Digital Loop Carrier System Generic Requirements Objectives
Interface14 gives additional ABCD codes for non-locally-switched circuits such as
foreign exchange
6-110 SR-TSV-002275 SOC Notes on the LEC Networks 1994
Issue April 1994 SignalIng
Table 6-20 ABCD Codes Locally Switched Circuits IDT to RDT
ABCD Loop Ground Loop CoLn Multi- Code Start Start Reverse Party
Battery CF DTF
-R 0000 -R ringing -R ringing -R ringing -R ringing ringing
0001
0010 DSO AIS DSO MS DSO MS DSO AIS DSO MS DSO MS
0011
0100 RLCF RLCF RLCF RLCF
0101 LCF LCF LO LCF LCF LCF
0110
0111 DSO Yellow DSO Yellow DSO Yellow DSO Yellow DSO Yellow DSO Yellow
1000 Reserved Reserved Reserved Reserved Reserved Reserved
1001
1010 Pos Coin Pos Coin ringing
Check Check
1011 Neg Coin Neg Coin Tip Party Check Check Test
1100 Pos Coin Pos Coin ringing Control Control
1101 Reserved Reserved Reserved Reserved Reserved Reserved
Coin -T 1110 Neg Coin Neg ringing Control Control
1111 LCFO LCFO LC LCFO LCFO LCFO
Legend
AIS Alarm Indication Signal CF Current Feed
DTF Dial-Tone First LC Loop Closure LO Loop Open LCF Loop Current Feed RLCF Reverse Loop Current Feed LCFO Loop Current Feed Open
Reserved for superframe-to-exteuded superframe translation
6-111 BOC Notes on the LEC Networks 1994 SR-TSV-002275 issue 1994 Signaling AprIl
Table 6-21 ABCD Codes Locally Switched Circuits RDT to IDT
ABCD Loop Ground Loop Coin Multi- Code Start Start Reverse CF DTF party
Battery
0000 Ring Ground
0001
0010 DSO AIS DSO MS DSO MS DSO MS DS0 MS DSO MS
0011
0100 RLCF
0101 LO LO LCF LO LO LO
0110
0111 DSO Yellow DSO Yellow DSO Yellow DSO Yellow DSO Yellow DSO Yellow
1000 Reserved Reserved Reserved Reserved Reserved Reserved
1001
1010
1011
1100
1101 Reserved Reserved Reserved Reserved Reserved Reserved
1110 Coin Coin Tip Party Ground Ground Ground
1111 LC LC LC LC LC
See Table 6-20 for legend
6.12 Multifrequency Pulsing
The multifrequency pulsing system consists of transmitting and receiving equipment for sending number information over trunks by combinations of two and only two of five
frequencies in the voiceband Each combination of two frequencies represents pulse The the channels and each pulse represents digit pulses are sent over regular talking
and since they are in the voice range are transmitted as readily as speech control Multifrequency receivers detect the pulses and transfer the digital information to equipment that establishes connections through the switches Multifrequency pulsing is in Automatic also used to transmit calling number information Centralized Message Accounting Automatic Number Identification CAMA-ANI operation In this case the calling number is multifrequency-pulsed forward from the originating office to the
CAMA office following the forwarding of the called number whether the called number is transmitted by multifrequency or dial pulsing The signaling used for equal access to
ICs sends the calling number first followed by the called number
The multifrequency pulsing system transmits numerical information and control signals therefore another signaling system for example digital carner single-frequency or loop
signaling must be provided for supervision Signals for control functions are provided by adding sixth frequency The six frequencies are spaced 200 Hz apart These six
frequencies provide 15 possible two-frequency combinations Ten combinations are used
6-112 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl gg4 Signaling
for the digits to inclusive and one each for signals indicating the beginning Key
Pulse and end STart processing of pulsing The remaining three
combinations are used for other signals Table 6-22 shows the digits or other usages and
the associated frequencies for the six-tone multifrequency pulsing code
Table 6-22 Multifrequency Codes
Signals
Frequencies Dgit and Inband and Expanded CC1TI Operator-Services System
In Hz Control Inband System Equal Access
700900
7001100 CoinCollect
7001300
7001500
7001700 Ringback Code 11 ST3P Si
9001100
9001300
900 1500 Operator Released
9001700 Codel2 STPSP
11001300
11001500
11001700 KP Coin Return KPI
1300 1500 OperatorAttachedt
1300 1700 KP2 sT2Psr
15001700 ST Coin Collect and ST
Operator Released
Expanded inband only
and The principal advantages of multifrequency pulsing are speed accuracy range
Multifrequency senders transmit more rapidly than dial-pulse senders Consequently
less time call As multifrequency signaling requires holding per result relatively
small number of senders or registers are used as common equipment for large number of trunks
Standards on multifrequency signaling are covered in TR-NWF-000506 Signaling Sections 6.1 6.4 TR-NWT-000507 Transmission Section IEEE STD 752-
1986 IEEE Standard for Functional Requi rements for Methods and Equipmentfor Measuring the Peiformance of Tone Address Signaling Systems and ANSI Tl.405-
1989 Inteiface between Carriers and Customer Installations Analog Voicegrade
Switched Access Using Loop Reverse-Battery Signaling.6
6-113 BOC Notes on the LEC Networks 1994 SR-TSv.002275 Signaling Issue AprIl 1994
6.12.1 Tones Sent by the Calling Station after Dialing
before the called Tone signals sent by the calling station after dialing but party answers can interfere with multifrequency pulsing As result data or other tone signals should handshake not be sent by the calling station before the called station answers Any tone signals should originate from the called station not from the calling station
6.12.2 MuItifrequency Transmitter
office typical plan of multifrequency pulsing begins when the originating gives connect signal to the distant end which returns off-hook supervision to delay pulsing idle until register is attached When the pulsing path has been completed to an receiver
The is then sent the supervision changes to on-hook as start-pulsing signal KP signal automatically followed by the digit tones and the ST signal
receiver for Besides At the distant end the KP signal prepares the multifrequency pulses informing the distant sender that no more pulses are to be expected the ST signal begins call processing in the distant office
6.12.2.1 Digit Duration
Multifrequency pulses are sent by transmitters in Stored-Program Control SPC offices The senders receive including those that serve as hosts for operator-services systems numbers from customers or from operators or other senders by multifrequency pulsing
DTMF pulsing or dial pulsing The senders transmit these numbers as multifrequency pulses The tones are generated by discrete oscillators in analog offices or read from read-only memory in digital offices The multifrequency senders associated with the
1/lA ESS switching system outpulse with pulses and interdigital periods of 60 0.5 ms for each rate of approximately 8.3 digits per second This rate is increased to 10 pps intercontinental dialing using CC1TF Signaling System No.5 The present and multifrequency pulsing rates as stated in the LSSGR are 58 to 75 ma for pulses interdigital intervals Other pulse and interdigital intervals are shown in Table 6-23
6-114 SR-TSV.002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SignalIng
Table 6-23 MF Sender Pulse and Interdigital Intervals
Pulse and Interdigital- KP
Intervalsms Signal
Switching Duration System Normal Optional ins
1/lA ESS 60 0.5 50 0.5
1/lA ESS HILO 60 0.5 50 0.5 120 0.5
2/2BESS 75 50 4ESS 70 50 100
5ESS 70 None 110 DMS-10 687 70 10010 DMS-100 70 70 100 EWSD 68 None 100 NEAX-61E 643 963 LSSGR 58-75 None 90-120
Adjustable in 10-ms steps from 10 to 2550 ms per trunk group
6.12.22 KP Duration
The KP signal duration is 90 to 120 ms The receivers are designed to accept KP
signal of 55 ms minimum but it is good practice for senders to outpulse KP signals near
120 ms to provide margin against transmission impairments such as delay distortion and Time Assignment Speech Interpolation ASI clipping The duration of the KP signal is given in Table 6-23
6.12.2.3 Transmitter Tone Level Frequency and Timing Limits
The normal power output of muhifrequency presently used is or dBm per
frequency at the TLP The frequencies of the oscillators should be within 1.5 percent
of nominal The levels of the two tones of digit should be within dB The older
equipment transmits -6 dBmO per frequency and the new equipment sends the BOC
standard of dBmO per frequency However there is no plan to change equipment using dBmO to the new level
The multifrequency tone leakage limit when no signal is being sent is 58 dBmO When
signals are sent the total extraneous frequency components should be at least 30 dB below of the level either of the two signal frequencies when measured over 3-kHz band
Most senders used in BOC switching systems are arranged so that under normal
conditions the two tones comprising multifrequency signal pulse are applied to the trunk simultaneously and neither tone is transmitted if either tone source should fail The
LSSGR requires that the transmitter start and end the two tones within ms of each other
6-115 BOC Notes on the LEC Networks 1994 SR-TSV002215 Signaling issue April 1994
the Multifrequency receivers however will recognize pulse as valid signal if two tones arrive within ms of each other
6.12.2.4 Transmitter Impedance
It is an LSSGR requirement for the transmitter to have the same nominal impedance as the office in which itis used that is 600to 900 Qin series with 2.16 MF When the connected to 4-wire carrier channel or to the 4-wire port of terminating set impedance should be 600 nonreactive The transmitter should have longitudinal balance to ground and return loss at least equal to that required for voice transmission
6.12.2.5 Tests of Multifrequency Transmitters
Multifrequency senders in electronic offices such as the 1/lA ESS switching system are tested by the receivers in the same office with circuit known as the multifrequency test in the environment circuit Each transmitter is tested against each receiver office as explained in the following material on receivers
6.12.3 Multifrequency Receiver
The receiver is connected to trunk as part of register as required It does not respond unit then receive and to voice-frequency currents until it receives the KP signal The can pass on the number codes and the ST signal to its associated equipment basic receiver design includes level-limiting amplifier feeding series of bandpass filters one for each of the six tones The output of each filter is rectified and used to trigger flip-flop indicating that the particular tone is present The tone pairs are then decoded into digits
Before this occurs however signal present ifiter and detector inhibit all the individual tone detectors unless signal of proper general frequency and level is present
The same functions of course can be done by digital signal processing
6.12.3.1 Receiver Limits
Existing mtiltifrequency receivers generally meet the LSSGR requirements below
Impedance The impedance of an analog receiver should match that of the end switching system that is 600 or 900 fl in series with 2.16 jiF When connected to 4- wire carrier channel or the 4-wire port of terminating set it should be 600 nonreactive The longitudinal balance to ground should be at least equal to that required for voice transmission
Tone Level The receiver should respond to signal levels between and 25 dBm per frequency or their digital equivalent Existing receivers may have sensitivity of only 22 dBm but new circuits should meet the 25 dBm requirement The receiver should not respond if the signal levels drop below 35 dBm per frequency
6-116 SR-TSV-002275 BOC Not. on th LEC Notwork 1994
Issu Ap.1I 1994 SignalIng
before Receipt of KP The receiver should not respond to address signals being unlocked by receipt of KP signal Simulation of the KP signal by speech or other
If signals or noise should not cause more than one lost call per 2500 calls two or more Once consecutive KP signals are received all those after the first should be ignored unlocked the receiver should remain unlocked until it receives the start signal ST SW
ST2P or ST3P In applications not using KP and ST signals the switching system should provide means of locking and unlocking the receiver
Digit Duration The receiver should respond to signals in which each frequency component duration is at least 30 ma The receiver should respond to KP signal that is atleast55 ms long and may respond if the KP signal is from 30 to 54 mslong The two frequency components may be shifted in time relative to each other by as much as ma due to Envelope Delay Distortion EDD in the transmission facility an extreme example taken from analog undersea cable facilities with 3-kHz channelization more typically 0.3 ma or less in an intraLATA network It is desirable that the receiver not respond to signals shorter than the requirements in the preceding part and it is required that it not respond to signals in which the two components are not coincident for more than 10 ma
The receiver should recognize interpulse intervals as short as 25 ma This interial is defined as the time during which no signal frequency component is above 35 dBm It is desirable that the receiver bridge interruptions as long as possible consistent with meeting the interpulse requirement It is required that it bridge interruptions up to 10 ma long after the minimum length signal has been received The receiver should accept up 10 to pulses per second
Two and Only Two Frequencies The receiver should check for the presence of only two valid frequency components in each pulse if pulse fails to meet this requirement the call should receive reorder treatment As an example of an alternative technique the DMS-100F switching system 6X92BB multifrequency receiver checks for all six valid frequency components in multifrequency pulse The two highest-level components are selected as the value of the pulse
Level Difference Between the Two Frequencies The receiver should tolerate pulses in which there may be as much as 6-dB difference in power levels of the two be tolerated frequency components It is desirable that even greater level differences
Existing receivers more than meet this requirement Multifrequency receivers in the
1/A ESS switching system are tested with 6.25-dB difference in power levels of the two frequency components
Maximum Length of Multifrequency Digits In ATT-made switching systems the only limit on the length of tune that multifrequency signals can be sent or received is the time-out interval of the multifrequency receiver This information is shown in Table
6-24 which shows that multifrequency digit must be completed in 10 seconds
6-117 BOC Not. on the LEC Networks 1994 SR-TSV.002215 Signaling issue Apili 1994
Table 6-24 Minimum Digit Timing
LSSGR
V.55 DM5-lOt DMS-100$ ObjecUve
DP MV DP MV DV MV DP MV
First be received in less from 16 16 2.30 2-30 16-24 5-10 digit must than_ses seanue 10
5-10 Each digit must be received within seconds after 16 2-30 2-30 16-24
previous digit
Second and third digits must each be received in less than 16
seconds from registration of previous digit
Fcwth digit must be received in less than seconds from 16
registration of third digit
after fourth be received in less than 16 Each digit digit must
seconds from of registration previous digit
All digits atbezeceivedinless thanseconds from 16 16 2-30 2-30 20
seizere 10 30
Note Includes both 3-and 10-digit register operation
Under overload conditions
Optional
All times shown are software settable from second to 155 second in I-second increments
1-second increments
Types and Levels of Noise The following types and levels of noise should be tolerated with an error rate of not more than one in 2500 10-digit calls
Message Circuit Noise Signal-to-noise ratio 20 dB
Noise ratio noise Impulse Signal-to-noise 12 dB test with impulse tape 201
The noise tape is covered in TR-TSY-000763 Digital Simulation Test di1ital Tape1
Power Line Induction 60 Hz 81 dBrnc0 180 Hz 68 dBmc0
The limits for impulse noise power represent levels that are exceeded not more than 15 times in 15 minutes
Tolerate lntermodulation Products The receiver should tolerate 2A-B and 2B-A intermodulation the and products where frequencies represent the digit being transmitted caused by transmission of multifrequency pulses over facilities The power sum of these modulation products is expected to be at least 28 dB below each frequency component of the signals
6-118 SR-TSV-002275 BOC Notss on the LEC Networks 1994
Issue AprIl 1994 SignalIng
Frequencies Accepted The receiver should accept 700- 900- 1100- 1300- 1500- and 1700-Hz signals within the limits of 1.5 percent Hz and 1.5 percentS Hz
Receiver Tests In some electronic switching offices each multifrequency receiver is tested with each multifrequency transmitter through an environmental test circuit The following tests are made
Flat Loss Test resistive pad is inserted between the transmitter and receiver
circuits This tests transmitter output level and receiver sensitivity
Twist Test network that attenuates the 1500-HZ signal 6.25 dB more than the
between the transmitter and receiver This tests the 700-Hz signal is inserted ability
of the receiver to respond to two multifrequency tones when one is at level
appreciably different from the other
and Double Keying Test third frequency is generated in this circuit applied to
the receiver at level dB higher than the tone pair from the transmitter This
simulates the type of signal produced when two multifrequency digits are sent
simultaneously The receiver should respond to all three tones and the program
should reject the signal as invalid
Modulation Products Test third frequency is generated in this circuit and
applied to the receiver at level 15 dB below the level of either tone in the pair from
the transmitter This simulates 2A-B intermodulation products produced by trunk facilities The receiver should respond only to the two tones from the transmitter
and should the third the when digit is being sent reject frequency When two tones
from the transmitter are absent however the individual channel detector although
not the signal present indicator should be operated by the third frequency
The DMS-100F switching system does not provide an environmental test circuit between the transmitter and receiver to mutilate the tones from the transmitter as they are looped to the receiver
6.12.3.2 Maximum Impairment
The multifrequency receiver should correctly detect valid digits and reject nonvalid tone or tones digits when all operating parameters are at their worst That is for valid digits the frequencies of both tones can be as far from normal high or low as allowed the tone level can be as high or low as allowed the twist can be at its maximum and noise as high as allowed and still detect valid digits
6.13 Dual-Tone Multifrequency Signaling
Dual-Tone Multifrequency DTMF signaling provides method for pushbutton the voice signaling from customer stations using transmission path This system provides
16 distinct signals Each signal uses two voiceband frequencies one from each of two
6-119 BOC Notes on the EEC Networks 1994 SR-TSV.002275 Issue 1994 Signaling AprIl
not groups of four tones each The tone frequencies are geometrically spaced
harmonically related
intraLATA networks Customer The requirements for DTMF signaling in the including Premises Equipment CPE using DTMF are covered in the following standards
BOC intraLATA networks TR-NWT-000506 Signaling Sections 6.1 6.42
BOC intraLATA networks TA-NPL-000912 Compatibility Information for
Telephone Exchange Service4
BOC intraLATA networks receiver for end-to-end signaling TR-TSY-000181
Dual-Tone Multifrequency Receiver Generic Requirements for End-to-End Signaling Over Tandem-Switched Voice Links17
Standard Measurements of DTMF signaling IEEE STh 752-1986 IEEE for the Functional Requirements for Methods and Equipmentfor Measuring
Performance of Tone Address Signaling Systems1
Telephones EIA 470-A-1987 Telephone Instruments with Loop Signaling8
and ANSI Tl.401-1988 Interface CPE using loop-start ground-start signaling Between Carriers and Customerinstallations Analog Voicegrade Switched Access
Lines Using Loop-Start and Ground-Start Signaling5
Between CPE using loop reverse-battery signaling ANSI Ti .405-1989 Interface Carriers and Customerinstallations Analog Voicegrade Switched Access Using
Loop Reverse-Battery Signaling6
CPE PBXs EIAITIA 464-A-1989 Private Branch Exchange PBX Switching EIA Equipmentfor Voiceband Application and inclusion of 464-1
6.13.1 DTMF Signaling Frequencies
shown in Table 6-25 The frequency pairs assigned for DTMF signaling are
See ANSI Ti .401-1988 or EIA11A 464-A-1989 for the exact current/voltage characteristics of terminal The dc resistance that will meet the during DTMF signaling and in the communications state highest
464-A.1989 for off-hook is 430 with 20 mA requirements of ANSI T1.401-1988 or EIA./TIA an the the current to 18 flowing During failure of primary power at serving switching system may drop mA
6-120 1994 SR.TSV002215 BOC Notes on the LEC Networks SignalIng Issue April 1994
Table 6-25 DTMF Frequency Pairs
High-Group Frequencies Hz
1209 1336 1477 1633
697 Low Group
Frequencies 770 Hz
852 .7
941
end- NOTE The and symbols are for new services At present the is an optional calls International Direct Distance Dialing of-dialing signal on some for example variable The standard for custom- to avoid timing when address lengths are customer to the central office calling services uses the format XXX as input
6.13.2 DTMF Central Office Receiver Operation
is described in the sections Operation of the central office DTMF receiver following
6.13.2.1 Input Impedance and Longitudinal Balance
for the DTMF receiver Minimum Input Impedance The minimuminput impedance is4O000 fromdcto4kHz
for DTMF Minimum Longitudinal Balance The minimumlongitudinal balance
Section 715 test in IEEE 455- receiver is 50 dB TR-NWT-000507 Transmission in the Voice 1985 Measuring Longitudinal Balance of Telephone Equipment Operating loss Ban4 Test Procedures for1 can be used to verily the return
6.13.2.2 Registration of DTMF Signals Without Noise
the listed above are Valid Tone Check The DTMF receiver checks that two of tones from each of four The receiver should ignore single present and that one is group DTMF tone
The receiver should the Simultaneously Operating Two Pushbuttons ignore simultaneously Most DTMF telephones will result of operating two DTMF pushbuttons valid or when two buttons are pushed simultaneously send single DTMF tone none
if the are Tone Frequency Limits The receiver should register the digit frequencies
but it if the deviation of either within 1.5 percent of their nominal values ignore
6-121 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Signaling
The Universal Tone Receiver UTR frequency is greater than 3.5 percent DMS-100F than will not totally reject digits whose frequencies deviate more 3.5 percent
receiver DTMF digits as Tone and Interdigital Time Limits The should register
in the first ins of the digit and should short as 40 ins transients can be present short 40 ins The shortest cycle time tone-on plus recognize interdigital intervals as as less than 23 should be tone-off interval that must be accepted is 93 ms Digits ms long
rejected
Transients Transients are defined as short-duration amplitude changes exceeding such transient should be restricted dB deviation fromthe steady-state signal.level Any The transient should not exceed 12 dB to the first ms of the tone-on interval peak of the above the steady-state peak amplitude composite signal
for in tone However the Gaps In Tone There is no requirement bridging gap interval Some receivers will receiver must recognize 40 ins of no tone as an interdigital interval recognize 20 ins or more of no tone as an interdigital
with Tone-Level Limits The receiver should register DTMF digits power per and with of to dB frequency of 25 toO dBm high-frequency tone power with termination bridged relative to that of the low-frequency tone as measured 900- termination of 900 across the receiver The overload level value of dBm assumes of the is below The receiver should not respond if either frequency component signal 900 fl -55 dBm into 900 In electronic switching offices the termination is
should be registered in the Digit Registration with Echoes DTMF digits accurately least that to 20 ins and reduced in level by at presence of signal echoes are delayed up
16 dB with respect to the primary signal
be in the of central office precise Dial Tone DTMF digits should registered presence
is dBm dBm dial tone Section 6.22.2 The level of the dial tone nominally 10 13 termination is at when 900- resistive test per frequency the point of application would be 1.5 for tolerance in tone substituted for the customer line The worst case dB Line mismatch for 2-wire level or 8.5 dBm for both tones at the source impedance The worst case for 2-wire office is office may increase the dial tone another dB the 5.5 dBm for both tones at the receiver In 4-wire and digital offices trans-hybrid 4-wire and offices should be loss reduces the dial-tone level at the receiver Thus digital
of dial tone at -133 dBm able to register DTMF signals in the presence
in Presence of Gaussian Noise 6.13.2.3 Digits Registered
be with low error rate in the presence of Low-level DTMP digits should registered
Gaussian noise Details of this test are as follows
with rate of Error ratio should be less than one error in 10000 pulses DTMF pulsing and 50-ms interval All DTMF digits 10 pps with 50-ms tone-on time interdigital should be incorporated in the sequence of pulses
6-122 the LEC Networks SR-TSV-002275 BOC Notes on 1994 Signaling Issue AprIl 1994
nominal level of dBm into 900-fl test Each DTMP digit should be at 22
termination The method of measuring the tone levels is shown in Figure 6-38
Figure 6-38 DTMF Digit Source
The noise source for the tests is shown in Figure 6-39 The noise generator produces Gaussian noise noise level of 45 dBm of flat-weighted 3-kHz band-limited as
measured in 900-fl test termination
900-Q Test Termination -45 dBm
10 dB Down at 310 and 3300 Hz
Figure 6-39 Gaussian Noise Source
The test DTMF receiver is connected to the digit and noise sources as shown in the Figure 6-40 The DTMF receiver is across 900-fl test termination during test 6-39 O-dB The levels of tone in Figure 6-38 and of Gaussian noise in Figure assume network has loss in the combining network of Figure 6-40 Where the combining
loss the levels of the tone and noise should be increased to compensate for the loss and the noise should be The level of the DTMF signals should be 22 dBm per tone
45 dBm at the receiver
of Noise Low-level DTMF should Digits Registered in Presence Impulse digits in the of noise Details of the test are be registered with low error rate presence impulse
as follows
level should be made For other than 9O0- applications an appropriate adjustment in voltage
6-123 SR-TSV002275 BOC Notes on the L.EC Networks 1994 Issue AprIl 1994 Signaling
50-ms tone-on time and 50-ms The DTMF pulsing rate should be 10 pps with should be in the of interdigital interval All DTMF digits incorporated sequence
pulses
Receiver Figure 6-40 Gaussian Noise Test of DTMF
dBm into Each DTMF tone should be at nominal value and at level of 22
is shown in 900-fl test termination The method of measuring the tone levels Figure 6-38
of dB at level than The noise level is set to signal-to-noise ratio 12 noise higher should be the 201 noise the signal The impulse noise source for the tests tape 20119 and shown in described in TR-TSY-000762 Impulse Noise Tape No Figure in 6-41 At this level there should be no more than 14 errors 10000 pulses 16.7 minutes
900-fl Termination
Calibration Tone -l2dBm
Source Figure 6-41 Impulse Noise
of an Ni carrier channel not equipped with Impulse noise tape No 201 is recording time of 30 minutes By varying compandors The tape has rnnning approximately
6-124 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue Apr11 1994 Signaling
line be the playback level of the tape wide range of noise can simulated
1000 Hz calibration tone at the start of the tape simplifies the noise level adjustment
The test DTMF receiver is connected to the digit and noise sources as shown in
Figure 6-42 This arrangement places the DTMF receiver across 9004 termination
during the test The levels of tone in Figure 6-38 and of impulse noise in Figure 6-41 assume 0-dB loss in the combining network of Figure 6-42 Where the combining
network has loss the levels of the tone and noise should be increased to compensate
for the loss The DTMF signals should be at 22 dBm per tone and the calibration be the receiver tone on the noise tape should 12 dBm at
Figure 6-42 Impulse Noise Test DTMF Receiver
Double-Digit Registration with Impulse Noise Double-digit registration of often in the of noise Details of single DTMF digit should not occur presence impulse this test are as follows
The DTMF pulsing rate should be pps with 180-ms tone-on time and 70-ms in the of interdigital interval All DTMF digits should be incorporated sequence
pulses
All other conditions for this test are the same as in this section
Extraneous Frequency Components The primary source of nonlinear distortion
facilities like in the DTMF signal is the DTMF telephone However single-channel loop carrier systems may also introduce distortion Nonlinear distortion produces extraneous interfere with receiver frequencies that accompany the DTMF signal and may operation The nonlinear distortion requirement for DTMF receivers is defined as the total power of
be tolerated in the voiceband above these extraneous frequencies that must 500 Hz
The is follows relative to the power level of DTMF signal requirement expressed as the receiver should tolerate signal-to-distortion ratio of 20 dB relative to the two-tone
6-125 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaling
level of DTMF and ratio of 16 dB with respect to any DTMF power signal single tone from EIA 470-A-1987 Telephone Instruments with Loop Signaling
Digit Simulation The average rate of digit simulation by speech room noise etc
and intervals should be less than one prior to DTMF signaling during interdigital in 2000 calls for occurrence in 3000 calls for digits through one occurrence digits combinations through plus and and one occurrence in 1500 calls for all 16
make such The above data was collected from actual 7-digit calls Since the facilities to and technical of the test are not widely available digit simulation test tape description Test to tape are available as TR-TSY-000763 Digit Simulation Tape16 replace testing
filter that is 10 dB on actual calls When this tape is played back through band-pass of into the same down at 300 Hz and 3000 Hz and at calibration level 20 dBm type numbers should be of receiver as was used to collect this data the following developed There should be no more than 670 total simulations of the 16 DTMF tone pairs in this and than 170 simulations total not more than 330 simulations of the digits 0-9 no more
of the signals or
6.13.3 DTMF Receiver Test Circuit Operation
The DTMF receiver test circuit operation is described in the following sections
6.13.3.1 Automatic Tests in 1/lA ESS Switching System
made Automatic tests of the DTMF receiver in the l/lA ESS switching system are as
follows
High Band Edge and Low Band Edge Tests The receiver must correctly receive
digits
Level-per-tone 22 dBm 900
nominal Frequencies 1.5 percent above nominal and 1.5 percent below
Digit length 40 ms
Interdigit length 40 ma or greater
Overload Test The receiver must correctly receive digits
Level-per-tone dBm 900
Frequencies 1.5 percent below nominal
Digit length 40 ma
Interdigit length 40 ma or greater
6-126 SR-TSV002275 BOC Notes on the LEC Networks 1994 Signaling issue AprIl 1994
Out-of-Band Test The receiver must ignore the following
Level-per-tone dBm 900
Frequencies 3.5 percent below nominal
Digit length 70 ms
Interdigit length 70 ms
Third-Frequency Test The receiver must ignore the following
Level-per-tone 10 dBm 900
Frequencies nominal
Digit length 70 ms
Interdigit length 70 ms
Third frequency 2000 Hz
Third frequency level 10 dBm 900 fl
the Low-Group Only and High-Group Only Tests The receiver must ignore
following
Single-frequency tone 2600 Hz
Level 10 dBm
Frequency nominal
Digit length 70 ms
Interdigit length 70 ins
6.13.3.2 Low-Level Test
without automatic can be made with Low-level tests of DTMF receivers in offices testing -22 into 900-a test termination source of DTMF digits adjusted to send dBm dB
6.13.4 DTMF Station Test Receiver Operation
is described in the following Operation of the DTMF station test receiver operation sections
6.13.4.1 Input Impedance
identical to and be bridged The station test receiver should have an input impedance the service receiver of the particular across the loop termination at the same point as
central office
6-127 BOC Notes on the LEC Networks 1994 SR-TSV002275 issue April 1994 Signaling
6.13.4.2 Band Edge Frequencies
centered at 1.5 of the The band edge frequencies of the test receiver should be percent
nominal DTMF frequencies and held to tolerance of 0.2 percent
6.13.4.3 Effective Sensitivity
should be more restrictive than that of the service The effective sensitivity 11 dB the service that is it receiver and should tolerate the same range of twist as receiver
should tolerate difference.in the high-frequency level with respect to the low-frequency
level of to dB
6.13.4.4 Limiting Pulsing Speed and Pulse Duration
and duration that will be by test receiver The limiting pulsing speed pulse accepted
test circuit for DTMF automatic dialers are as when working in conjunction with speed follows
and shorter than 43 ms should Signals of 48 ms or more should be accepted signals
be rejected
should be and intervals shorter than Interpulse intervals of 45 ms or more accepted
40 ms should be rejected
times of less than 93 ms Cycle time of 97 ms or more should be accepted and cycle
should be rejected
6.13.5 In-Service Receivers and Transmitters
6.13.5.1 Use of Number Sign
EWSD and Some DTMF receivers like those used in 1/lA ESS DMS-100 DMS-lO
will the DTMF as an end- NEAX-61E switching systems interpret digit number sign the number can be used to eliminate time-out when of-dialing signal In this case sign offices send the DTMF variable number of digits can be expected Operator-services to of the Card Service tone to release any DTMF dial-pulse digit as part Calling prompt
converter in the connection
6.13.5.2 DTMF Receiver Start Dialing Signal
Customer Dial-Pulse and DTMF Receiver The 1/lA ESS switching system or except dial receiver on lines does not provide any start signal wink-start delay-dial tone
6-128 SR-TSV-002275 BOC Notes on the LEC Networks 1994 SIgnaling Issue April 1994
Private Network DTMF Receiver There is DTMF receiver used in the 1/lA ESS software switching system that sends controlled-outpulsing start signals wink-start or
receiver is delay-dial It is used on private network signaling and DOD However the receiver has the not found in all offices It connects to trunks with trunk features The following characteristics
Section It meets the requirements for central office receiver see 6.13.3
Both common-control and manual DTMF outpulsing are received
The receiver will provide dial tone wink-start or software delay-dial signal to the
connected trunk when ready to receive information However given trunk cannot send both dial tone and wink-start signal
6.13.5.3 DTMF Transmitters in Electronic Switching Systems
The l/lA ESS DMS-1O DMS-lOO EWSD and NEAX-61E switching systems can other location The provide DTMF transmitter for outpulsing to PBX Centrex or either line trunk functions transmitter always connects to trunk circuit that has or
trunk circuit with line functions is used when line is the connecting circuit at the distant
end and trunk circuit with trunk functions is used when trunk is the connecting circuit The conditions for the transmitter are as follows
The tone level is dBmO 1.0 dB per frequency
The frequency tolerance of individual frequencies is 1.5 percent
should When DTMF digit is being sent the total extraneous frequency components when be at least 30 dB below the level of either of the two signal frequencies
measured over 3-kHz band
The tone leakage limit when no DTMF digit is being sent is 58 dBmO or less
the trunk or line The DTMF transmitter applies both tones of the DTMF digit to
simultaneously and neither tone is sent if either tone source fails
The DTMF transmitter is arranged to delay the first pulse at least 70 ma after the
is start-dial start-dial signal or 70 ma after seizure if there no signal
is The digital and interdigital interval 500.5 ma
The transmitter operates wink-start or delay-dial expected to trunks it operates
ground-start to lines
to either lines or trunks There is no option to operate dial-tone start or stop-go
trunks The transmitter can operate immediate-start on lines or
used in In DTMF signaling there are no equivalents of the KP and ST signals
the can be sent as last signal to systems that multifrequency pulsing However
will accept it as an end-of-dialing signal
6-129 SR-TSV.002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Signaling
6.13.6 Barriers to End-to-End DTMF Signaling
There are several barriers to end-to-end DTMF signaling First some switching systems
the call This can disable the DTMF pad unless reverse the polarity on the line during included to coin totalizer operation and polarity-guard circuit is Second permit proper coin the normal negative battery supply to prevent fraud in many single-slot telephones This disables the DTMF from the end office is replaced with positive battery supply attenuate the DTMF enough pad Third echo suppressors where still found can signals is used to cause signaling failures if dial-tone start
end-to-end service voice mail radio paging It is important to be able to signal Banking and services end-to-end services answering machines many more depend upon 6.15.3 for of end-to-end in Feature Group signaling See Section an application signaling
6.13.6.1 Polarity Guard
attached to that changes To enable DTMF signaling in telephone switching system can be to the telephone This provides line polarity during call polarity guard applied the of the line proper polarity to telephone regardless polarity
6.13.6.2 Enabling DTMF Signaling in Single-Slot Coin Telephones
has ramifications Briefly Enabling DTMF signaling in single-slot coin telephones many enablement in some while preserving complete DTMF signaling switching systems and fraud one of two things proper coin totalizer operation prevention requires
in the coin station and Automated Coin Toll Service ACTS polarity guard office features in the operator-services
and Card Service Dial-tone-first features in the end office switchingsystems Calling
Dial-tone-first is covered in Section 6.18 features in the operator-services offices WT-00027 OSSGR Services Calling Card Service is covered in FR-N Operawr
Systems Generic Requirements.20
6.13.6.3 Effects of Time Assignment Speech Interpolation
switch call to only when speech is During busy traffic periods TASI systems facility the first few milliseconds of or signaling are present This means that at least speech For is to path through the clipped when switching necessary provide system which an internal signaling information on which talker or signal is switched to facility
is the internal not keep up system is used When traffic heavy signaling system may not be voice channel available for with the necessary changes and in fact there may
the speech or signaling
6-130 SR-IS V.002275 SOC Notes on the LEC Network 1994
Issue April 1994 Signaling
be found interLATA TASI originally was used only on overseas calls Now it can on carriers and private networks The result is shortened signaling digits on end-to-end signaling Where signaling failures occur due to TASI longer DTMF digits should cure the problem
6.13.6.4 Effect of Echo Suppressors and Dial Tone on DTMF Signaling
The effects of echo suppressors used by the various ICs and in the non-LEC networks that can be connected to LEC networks is unknown In general the makeup of these networks is unknown to the LEC Inthe past multifrequency pulsing see Section 6.12 had was universally used by the ICs This meant that multifrequency pulsing to pass through the various links of the network As result end-to-end pulsing that used the of levels and timing of multifrequency signaling would have an excellent chance working However multifrequency address signaling is giving way to CCS In addition of transmission before SPC switching systems echo suppressors were always part the address had the echo facility As result multifrequency signaling to pass through of the Even suppressors Now many of the echo suppressors are part switching system the if multifrequency signaling is used the multifrequency signals may not pass through echo suppressors At the same time echo suppressors have widely been replaced by echo cancellers which are much less troublesome
In summary the fact that the interLATA carrier or private network can signal to set up connection has no bearing on whether the transmission link can be used with end-to-end signaling
will There is no guarantee that end-to-end DTMF signaling with dial tone present always work over facilities using echo suppressors When DTMF signaling is transmitted over facilities using echo suppressors and dial tone is sent from the incoming switching system there is some risk that the first DTMF signal will be attenuated over the entire follows digit or over the first portion of the digit as
The attenuation varies from zero loss to complete blockage of tone depending on the
relative DTMF and dial-tone levels at the echo-suppressor location Under adverse
echo is The used in the conditions typical loss for an suppressor dB EST 4ESS
15 of the tone levels at the switching system introduces to dB loss depending on
EST using split operation
In many of these unfavorable circumstances the attenuation will occur over only the of the be first portion of the pulse The attenuated portion pulse can as long as 64ms
One solution is to use DTMF-to-dial-pulse converters when pulsing over facilities using This that dial- echo suppressors and dial tone must be used as start signal assumes
converter is pulse signals can be used end-to-end and that the DTMF-to-dial-pulse always on the line Those assumptions restrict this solution to private networks In situations where the dial tone can be reduced in level or eliminated by using zip tone or an be sent announcement link-by-link or end-to-end DTMF signaling can successfully
6-131 BOC Notes on the LEC Networke 1994 SR-TSV-002275 issue 1994 Signaling AprIl
the circuit Another approach is to place echo-suppressor disabler tone 2125 Hz on just before dial tone is applied If the dial tone is applied while the disabler tone is present
dial is and the tone is then removed the suppressor will remain disabled until the tone removed
time the rather than If the DTMF-tone signals originate in transmitters that pulses
first of near 120 can telephones that generally do not time the DTMF signals digit ma reduce failures caused by echo suppressors and TASI systems
6.13.7 Increased Sensitivity DTMF Receiver for End-to-End Signaling
converters or to alter the dial In many cases it is not possible to use DTMF-to-dial-pulse the tone to permit end-to-end signaling Another look at the problem has produced The receiver have been and following possible solution suggested concepts tried they
work However presently there is no known commercial receiver that meets these requirements The method will not be effective however if the call is cut-through to tie-line dial-9 access another dial tone and normal sensitivity receiver for example in or
situations It also will not be effective if the DTMF tones are about dB with respect will to the dial tone and the 4ESS switching system EST is used In this case the EST completely suppress the DTMF signals
The complete requirements for this receiver are in TR-TSY-000181 Dual-Tone Tandem- Multifrequency Receiver Generic Requi rements for End-to-End Signaling Over Switched Voice Links.17 Briefly these requirements increase the sensitivity of the This 1-dB DTMF receiver from 25 dBm per frequency to 36 dBm per frequency
when the echo is in the increase in sensitivity permits receiving DTMF digits suppressor double-talk mode The double-talk mode adds up to 15 dB of attenuation to the circuit
in both directions depending on the tone levels at the echo suppressor The increased of the central office sensitivity DTMF receiver uses many the same requirements as
receiver However the other requirements are more stringent as follows
20-ms echo Echo The receiver must meet the same signal-to-echo requirement at of 24-dB delay as the central office receiver and add new requirement signal-to-
echo ratio at 45-ms echo delay
the Gaussian Noise The receiver signal-to-noise ratio stays the same 23 dB
above the level dBm pulse signal level is reduced to dB minimum accept 33 per See and 6-40 for tone The error rate stays the same Figures 6-38 6-39 information on how to run the tests
Impulse Noise The signal-to-noise ratio of 12 dB noise higher than signal the remains the same while the pulse signal level is reduced to dB above minimum
The rate remains the same errors in 10000 digits accept level 33 dBm error 14 See Figures 6-38 6-41 and 6-42 for information on these tests
The receiver to minimize false Adaptive Sensitivity may use adaptive sensitivity
the first is the digits from echoes and speech When pulse received sensitivity below the received level threshold of the receiver would be raised instantly to dB
6-132 SR-TSV-002275 BOC Notes on the L.EC Networks 1994 Issue Ap1I 1994 SIgnaling
would be for the of the first pulse In most situations this new sensitivity satisfactory
rest of the digits on this call
6.14 Calling Number Delivery
CLASSSM Number Frequency shift keying is used by the Calling Delivery CND the called feature This feature delivers the calling customers directory number to CPE
the the information over the tip-and-ring of the line Along with directory number
is received by the customer contains the date and time of the call This information the delivered after the first full ring of the call.. If the call is answered before or during
data transmission the normal ringing trip occurs
then The CND feature can be turned on or off by going off-hook receiving dial tone and
the feature on until the customer turns it off dialing an appropriate code Once on stays
The control method is as follows
The first character is for DTMF and 11 for dial-pulse telephones
and for The suggested activation code is 65 for DTMF 1165 dial-pulse telephones
The suggested deactivation code is 85 for DTMF and 1185 for dial-pulse telephones CLASSM The CND feature can be blocked by method covered in TR-NWT-000391
number is Feature Calling Identity Delivery Blocking Features.21 When the calling number is not blocked is displayed in place of the calling number When the calling
available is displayed in place of the calling number Number The CND feature is described in TR-NWT-000031 CLAS Feature Calling Voicebaizd Data Deliveiy22 while the data interface is described in TR-NWT-000030
Transmission Inteiface Generic Requirements
6.14.1 Customer Considerations
the line If the The CND feature adds the ringer equivalence of the device to ringer
is the the addition of the CND feature equivalence of the line with CND above lixnit can be cured by could cause pretripping of the ringing signal Dial-pulsing problems Both replacing one or more of the dial telephones with DTMF pulsing telephones EIAITIA 464-A-1989 Private Branch Exchange PBX Switching Equipmentfor
Voiceband Application and inclusion of EJA 464-1 and ANSI Ti .401-1988 Interface Between Carriers and Customer Installations Analog Voicegrade Switched Access
CLASS is service mark of Beilcore
6-133 BOC Notes on the L.EC Networks 1994 SRTSV002275 issue 1994 Signaling April
indicate the allowable ac Lines Using Loop-Start and Ground-Start Signaling5
impedance and dc resistance for on-hook CPE
the SR-TSV-002476 Customer Premises Equipment Compatibility Considerations for
Voiceband Data Transmission Interface discusses compatibility aspects It
receivers with to on loops encourages the design of CPE enough sensitivity operate and switched ac termination meeting having normal amounts of bridged tap providing time of data Lack of the EIA 7-dB specification for return loss during the sending termination may result in delayed echoes circulating through Universal Digital Loop data Carrier UDLC systems with consequent failure to receive the accurately
of CPE connected to the BOC networks are covered The general electrical characteristics Serice.4 in TA-NPL-000912 Compatibility Information for Telephone Exchange
6.14.2 BOC Network Considerations
interswitch This service can be offered in SPC office for calls local to that switch For the calls CCS is required to send the calling number from originating switching system
or billing point to the terminating SPC switching system
feature bandwidth of only about 1000 to 2500 Hz is needed for the CND However be able to transmission in the on-hook state any loop carrier system used must provide ratio The central-office transmitter must meet limits for return loss and signal-to-noise
6.14.3 Data Interface
called but the called The serving SPC switching system transmits information to the end mark end does not transmit information to the central office Two frequencies 1200 Hz
transmit the information at rate of or and 2200 Hz space or are used to 1200 bps
6.14.3.1 Data Parameters
follows The parameters of the data interface are as
Link Type 2-wire tip-and-ring of the customer line
.Transmission Format Analog phase-coherent frequency shift keying
Application of Data Serial binary asynchronous
Bit Error Rate BER Less than one out of every 100000 bits at switching system interface
service end of Phase Continuity Maintained from initial to message
6-134 Networks SR-TSV-002275 BOC Notes on the LEC 1994 SignalIng Issue April 1994
of data into Transmission Level 13.51 dBm at point application
resistive load of 900
duration Bit Duration 833 30 p.s start and stop bits same
as standard bit
6.14.3.2 Data Protocol
and is described in detail in The message format is shown in Figure 6-43 more TR The NWT-000030 Voiceband Data Transmission Interface Generic Requirements and asynchronous protocol used in this interface provides data transmission error
checking as follows
The protocol uses words that are 8-bit data bytes each Each word-per-byte is
and followed bit preceded by start bit space logical by stop mark logical
The bytes are sent with the least significant bit first
each Message type message length and error detection checksum word are single word-per-byte The value of the byte is encoded in binary as follows
Message type for CND is 400000100
Message length is the number in binary of the data words sent
module 0-256 of the Checksum word is the twos complement of the sum message 0-256 type message length and the data words The CND adds the module sum checksum of the message type message length and the data bytes received to the is This word If the message has been received without error the result zero check method will detect most transmission errors if an error is detected will
be displayed in place of the data
Figure 6-43 Calling Number Delivery Message Format
ASCII characters to Data is one or more words-per-bytes Data words-per-bytes are
characters to be sent The and permit alphabetic as well as numeric alphabetic bits As the most numeric characters are 128 in number using seven binary result
of the data will be zero ASCII characters are significant digit byte 01000001 American National Code covered by ANSI X3.4-1986 Coded Character Set 7.bit
for Information Exchange
6-135 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 Signaling
The meanings of the various data words-per-bytes are as follows
The first two words are the month for example March would be 03
ThethirdandfourthwordsarethedayOfthemOnth
in 2.4-hour The fifth and sixth words are the hour of the day time for example PMis 1300
The seventh and eight words are the minute of the hour
number The rempining words are the calling partys dialing
6.14.3.3 Data Timing
in 6-43 The of the data is The order of the data signals is covered Figure timing signals
as follows
in the first silent interval that is should not The data signals are sent long signaling coded used begin until after silent interval of 525 ms to avoid the ringing patterns least 475 in Distinctive Ringing/ Call Waiting The data signals are completed at ms
before the end of the silent interval
of octal 125 The channel seizure signal is 30 continuous bytes 01010101
of mark is sent to condition Following the channel seizure signal 150 25 ms signal in 6-43 the receiver This signal is shown as carrier signal Figure
word After the carrier signal the data signals for message type word1 message length 20 of and data words are sent There should be no more than bit-periods 16.5 ms
silence between the data words
6.15 LATA Access
end office to IC INC and The following sections cover the signaling from an an or an
end office from an IC or INC Detailed information on LATA access signaling to an of the network design and configurations is discussed in Section comparison methods of LATA access is made in Tables 6-26 and various feature groups for providing 6-27
as follows Generic requirements that apply to LATA access are
FR-NWT-00027 OSSGR Operator Services Systems Generic Requirements
TR-NWT-000505 Call Processing Section 57
6.42 TR-NWT-000506 Signaling Sections 6.1
6-136 the LEC Networks SR-IS V-002275 BOC Notes on 1994
Issue April 1994 Signaling
Table 6-26 Feature Group Comparison
Condition
Access Codes 7-Digit 7-Digit None 1OXXX INPA-NXX-XXXX l95OWXXXs
Trunk Trunk Trunk Type of Termination Line
MTS/WATS-like MTS/WATS MTSIWATS Typical Service Use Foreign Exchange ONAL MTS/WATS-like MTS/WATS-likc open end open end open end
Address Signaling
Origmating MF/SS7 Prom EAEO to IC/INC Ringing Sein MF NA From EO to IC/INC Ringing Seimre DP MF MF/S57 From AT to IC/INC NA Seuro NA
From Stalion to IC/INC DTMF DTMFt NA NA
Terminating
MF/SS7 From IC/INC to EAEO DP DTMF MF MF NA From IC/INC to EO DP DTMF DP MF DP MF
MF/SS7 From IC/INC to AT NA MF NA
Billing Identification
Calling Station ONI DTh AN ON DTMFt AN ON AN From Station From Station DTMF DTMF Carriers Credit Card ON DTMF ON DTMFt ON ON From Station From Station From Station From Station
Super.ision Yes Yes From Calling Station Yes Yes
to IC/INC
Called Station Answer NA Yes Yes Yes
to IC/INC
Called Station Answer to NA No Yes Yes
Originating EO or EAEO
NA Not Applicable WOorl
DP is an option with the 1/lA ESS switching system
Presubseription can be used in lieu of the IOXXX earner access code
6-137 BOC Note on the LEC Network 1994 SR-TSV-002275 Issue 1994 Signaling April
Table 6-27 Availability of Feature Groups
Feature Group
Switching
System EO AT EAEO5 AT
1/lA ESS Yes Yes Yes Yes Yes Yes
1A ESS HILO Yes Yes NA Yes NA Yes
ESS Yes Yes NA Yes NA NA
2BESS Yes Yes NA Yes Yes NA
4ESS NA NA Yes Yes NA Yes
5ESS system Yes Yes Yes Yes Yes Yes
DMS-lO-100F Yes Yes Yes Yes Yes Yes
EWSD Yes Yes NA Yes Yes NA
NEAX-61E Yes Yes Yes Yes Yes Yes
NA Not Applicable
When signaling between EAEO and an IC is multifrequency
in one link and Signaling System SS7 in the
other some limitations apply
6.15.1 Carrier Classification
the carrier the various calls because the use of It is appropriate to classify handling with the of carrier the call Carriers be certain protocols is associated type handling may classified as follows
connections between Interexchange Carrier IC These are carriers providing in World LATAs and serving areas where the calling and called customers are Zone
connections International Carrier INC These are carriers that generally provide between customer located in the contiguous 48 United States and customer between located outside World Zone INCs may also provide connections located in World customer located in the contiguous 48 United States and customer
Zone outside the contiguous United States
Consolidated Carrier ICand INC These are carriers that provide connections as
described in both of the above
6-138 Network SR-TSV-002275 BOC Notes on the LEC 1994 SignalIng Issue April 1994
6.15.2 Feature Group
service and Feature Group FGA is line-side access that includes foreign exchange FGA interLATA Off-Network Access Line ONAL service from private networks can or All be arranged for originating-calling-only terminating-calling-only 2-way calling
end office switching systems used by the BOCs can provide FGA The line supervisozy as in Section 62 on access line signaling for FGA may use ground-start or loop-start
signaling
the Plain Old Service Access to an IC is made by placing call to 7-digit Telephone from POTS number of the carrier The connection to the carrier is no different any non-coin other local or toll call in the LATA The call can be made from coin or line
call from the to the IC must be for by and may involve an operator The originator paid
the originator to the LEC
the from the to the After the originator is connected to ICIINC signaling originator carrier must be by an inband method such as DTMF for both the called number and
The format of the for the called and identity of the calling party signaling calling
the IC/INC The carrier will bill the for the number is the responsibility of originator
interLATA portion of the call
The number Calls from an IC/INC into LATA are connected to POTS line telephone
The protocol is of the called party is entered by dial-pulse or DTMF signaling signaling in the of the call no different than on any other call to POTS line As case originating within the LATA all of this section applies
in The call will be controlled by calling-customer control of disconnect as described called Section 6.4.3 The IC/INC does not receive answer supervision from either the or
lines to connect to the and the calling line If the carrier uses ground-start originating on-hook after the disconnect terminating LATAs the IC may get an signal appropriate timing Table 6-8
More information on FGA is available in the following documents
0027 TR-TSY-000697 Feature Group FSD 2O24O2
TR-NWT-000505 Call Processing Section
6.42 TR-NWT-000506 Signaling Sections 6.1
All of the above documents are modules of FR-NWT-000064 LATA Switching
Systems Generic Requirements ISSGR.1
6-139 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling Issue April 1994
6.15.3 Feature Group
Feature Group FGB is trunk-side access arrangement Calls to the IC/INC use the telephone number 950-WXXX where equals or The call may go directly from the end office or be tandemed through second office known as an access tandem to reach the carrier The access tandem may serve only FGB functions or may provide multiple functions Calls from the IC/INC can go directly to the end office or can be
switched through the access tandem to reach it AM can be furnished optionally on most direct connections between the end office and the carrier ANT information cannot currently be furnished on tandem connections The signaling format used in calls from the end office to the carrier without ANT is shown in Figure 6-44 from the end office to the carrier with ANT is shown in Figure 6-45 from an end office tandemed through the access tandem to the carrier is shown in Figure 6-46 and from the carrier through an access tandem to the end office is shown in Figure 6-47
Any switching system can be used as an FOB end office as long as the calls are routed through an access tandem In fact any switching system can be used as an end office that connects directly to carrier if the office can translate the seven dialed digits on outgoing calls and provide AMA records on both incoming and outgoing calls With these restrictions end offices that can connect directly to carrier are usually limited by practical reasons to SPC switching systems such as 1/lA ESS 5ESS DMS-l0 DMS
100F and NEAX-61E For all the same reasons the access tandems are usually limited to 1/lA ESS 4ESS 5ESS DMS-100F and NEAX-61E switching systems Table 6-27 shows the FOB arrangements currently available
The protocol for interLATA calls involves signaling sequences and times between signals that do not exist in intraLATA calls as follows
Calls from an end office or access tandem
The carrier returns wink signal within seconds of trunk seizure
The carrier returns an off-hook signal within seconds of completion of the
address outpulsing
Calls from carrier to an end office or access tandem
The end office or access tandem returns the wink-start signal within seconds of
trunk seizure
wink The carrier starts outpulsing the address within 3.5 seconds of the
The carrier completes sending the address sequence within 20 seconds
6-140 SR-TSV-002275 SOC Notes on the LEC Networks 1994
Issue AprIl 1994 SignalIng
EO FGBlnterface IC
After Customer Dials 1950 WOX
SeIze
WInk
KP-STorKP950WOOST
Off-Hook
True answer signal not provided
EO Connects Talking Path
______ConversatIon Interval ______
Customer On-Hook
EO Disconnects
IC/iNC Disconnects
ANI Direct Connection 6-44 Originating Signaling Sequence Without Figure FGB
6-141 SR.TSV002275 BOC Notes on the LEC Networks 1994 Issue Apr11 1994 Signaling
FGB Interface
After Customer Dials 1950 WXXX
Seize
WInk
KP.ST0rKP950WXXXST
Off-Hook
True answer signal not provided KPi7DSTANI 5-
EO Connects Talking Path
Conversation Intervai
Customer On-Hook
EO Disconnects
IC/INC Disconnects
With ANI Direct Connection FGB Figure 6-45 Originating Signaling Sequence
6-142 SRTSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Signaling
EO
FGB interface
After Customer Dials 1950 WOX
SeIze
Wink
KP950WXXXST
Seize
Wink
KP-STorKP-950WOcXST
Off-Hook
EO/AT Connects Talking Path
10 Conversation Interval
Customer On-Hook
11 EO Disconnects
12 AT Disconnects
13
True answer signal not provided
Tandem Connection FGB Figure 6-46 Originating Signaling Sequence EO
6.143 BOC Notes on the LEC Networks 1994 SR-TSV-002276 Issue 1994 Signaling AprIl
EO
AT
SeIze
Wink
KP7orlODST
Wink
KP7DST
Ringing
Answer
Off-Hock
rrue answer signal Off-Hook 10 rne answer signal
11 ICIAT/EO Connects Talking Path
12 Conversation Interval
13 IC Disconnects
14 AT Disconnects
15 EO Disconnects
Tandem FGB Figure 6-47 Terminating Signaling Sequence
6-144 SR-TSV002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SignalIng
office and or access tandem and carrier can Supervisory signaling between the end carner for interoffice calls However or be any of the types mentioned in this section loop and is used on EM signaling is usually used on 1-way trunks EM signaling usually connection of the 2-way trunks where individual trunks are used In addition direct
carrier be at ends switching system to digital can made one or both
the carrier is Address signaling from the calling party to usually voice-frequency number and of the signaling such as DTMF for both the called identity calling party end offices Address However dial-pulse signaling can be used from suitably equipped from the carrier to the end office the exchange Either dial-pulse signaling depends upon In or wink-start or multifrequency signaling maybe necessary addition delay-dial
outpulsing control may be used
the The On outgoing calls from LATA the call will be controlled by calling party other on- IC/INC will receive calling-party disconnect supervision but not flashing or disconnect hook signals shorter than
On outgoing calls from LATA the end office or access tandem does not receive true the called answer supervision from the carrier The IC/INC sends an off-hook before
number or calling-party identity is accepted
from the On incoming calls to the LATA the carrier will receive supervision calling
It will also receive and other on-hook party to the called party flashing signals
will receive off-hook On incoming calls to the LATA the end office or access tandem be true from supervision from the IC/INC This supervision may or may not supervision from the on-hook seen an the calling party To prevent false disconnects signals by 12 seconds incoming office the BOCs use disconnect time of at least 10 to
Further information on FGB is available in the following documents
TR-TSY-000698 Feature Group FSD 2O-24-O3OO
TR-NWT-000505 Call Processing Section
6.42 TR-NWT-000506 Signaling Sections 6.1
All of the above documents are modules of FR-NWT-000064 LATA Switching
Systems Generic Requirements LSSGR1
TR-NPL-000 175 Compatibility information for Feature Group Switched Access
Service.29
6.15.4 Feature Group
used between the BOC and Feature Group FGC contains the arrangements originally the used to ATT for provision of switched-access services It includes arrangements discussed in this section It can be interfaced provide DDD and operator-handled calling
it that would be used only until as indicated in Table 6-26 Originally was thought FGC However the in equal access was implemented under Feature Group plans many
6-145 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling Issue AprIl 1994
BOC intraLATA networks have changed Many BOCs now plan to leave FGC in place
until CCS is available in the LATA
Other information on FGC is available in the following documents
TR-NWT-000504 Features Section 430
TR-NWT-000505 Call Processing Section
TR-NWT-000506 Signaling Sections 6.1 6.42
All of the above references are modules of FR-NWT-000064 LATA Switching
Systems Generic Requirements LSSGR1
FR-NWT-000271 OSSGR Operator Services Systems Generic Requirements.20
6.15.5 Feature Group Equal Access
Feature Group FGD consists of Equal Access End Office EAEO-to-ICIINC EAEO-to-access tandem and access tandem-to-carrier interconnection arrangements and Most switching equipment such as 1/lA ESS 5ESS DMS-l0 DMS-100F EWSD be used NEAX-61E provides EAEO features Dial-pulse signaling as well as DTMF can
from the calling telephone
In EAEOs the customer dials an access code of 1OXXX to identify the desired carrier caller to FGD has presubscription feature that eliminates the need for presubscribed dial the 1OXXX carrier access code See Section for dialing procedures The desired covered in detail in carrier is identified by XXX the carrier identification code FGD is the following
TR-NWT-000690 IC/INC Interconnection FSD 2O24OOOO31
TR-NPL-000258 Compatibility Information for Feature Group Switched Access Serice.32
In addition to regular message service FGD is used for exchange access for such digital
56 64 clear and ISDN applications as switched kbps service access
6.15.5.1 Equal Access End Office
usual If not In an EAEO the calling party enters all the address information as the DTMF the access-code presubscribed to carrier calling party can rotary-dial or in this to indicate whether the 1OXXX This is followed by or if is required area
need it the 7- or call requires operator assistance or does not Then 10-digit
is dialed telephone number of the called party
the carrier needs Service Signaling from the EAEO depends on whether Operator features such as hold recall Signaling OSS OSS provides operator operator operator limited direct trunk between the ringback and coin control signals OSS is to groups method is EAEO and the carriers OSS When OSS is not needed second signaling
6-146 BOC Notes on the LEC Networks 1994 SR-TSV-002275 SignalIng Issue AprIl 1994
EAEO to an IC/INC or trunk from used that permits direct trunk groups from an groups calls to an access tandem to the carrier With the second method of signaling an operator
can be made but the operator features of OSS will not be available
6.15.5.2 Operator Service Signaling
in offices with 5E4.2 or OSS features are available in all TOPS offices and OSPS generic in DMS-10 and later In the EAEO these features are now available ESS 5ESS DMS-100 switching systems
used to OSPS or TOPS offices OSS is very similar to multifrequency signaling signal follows when used in Feature Group Section 6.19 The differences are as
Two information digits are used in the ANT information sequence
the information can be either ST The multifrequency signaling start digit on ANT of interLATA calls or Si intraLATA calls This permits identification interLATA versus intraLATA calls without translating the dialed digits at the
the start ST was used with operator-service facility Previously only signal AM information
service can handle direct-dialed traffic Like the operator-services systems operator service can handle as well as assistance traffic and special-toll traffic Operator traffic and TOPS trunks and identify intraLATA interLATA and international OSPS
are usually 2-way
the will occur On calls to be routed to an operator-service facility following
The customer dials 1OXXX or 10 or 1OXXX 07 or 10 Table 6-28
The end office seizes an outgoing trunk
with standard wink The operator-service facility responds
of 40 200 ma The The end office outpulses the called number after delay to
outpulsing is KP 7/10 digitS ST SW ST2P ST3P
the will come Any time after the start of the ST pulse operator-service facility
off-hook to indicate readiness to receive ANT information
200 The The end office outpulses the ANT information after delay of 40 to ma outpulsingisKPll7digitsSTSTP On ANT failures KP02ST STP
will be sent OSS always includes ANT
format for interLATA or intraLATA calls to operator See Figure 6-48 for the signaling the used for to service All timing intervals are exactly same as signaling operator-
services systems
6-147 SR-TSV-00227$ BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaling
EAEO
OR After Customer has Completed Dialing 1OXXX 0I1NPA NO X0X 100X
SeIze
Wink
KP NPA NXX 000 ST STP ST2P ST3P or KP SIP ST3P
0ff-Hook
KP 117 Digits ANI ST STP
InterLATA or Figure 6-48 Originating Signaling Sequence Operator Services intraLATAFGD
Table 6-28 Feature Group Pulsing Format from End Office to Operator Service InterLATA and lntraLATA Calls
Screened TraMc 0- CoIn 0- 04- Non-coin and 0- ANI Type of Customer Muldfrequency-Pulsed Number Call Dials Called Number Calling
Non-coin
Direct dialed
ICP-7 or 10 KP-II-7 digits-ST Predesignated Carrier or 10 digits digits-ST2P KP-fl-7 Override Predesignation 1OXXX 7cr 10 digits ICP-7 cr10 digits-SflP digits-ST
Operator assistance 0- KP-ST3P KP-1I-7 digits-ST Predesignazed camer 00 KP-ST3P XP-ll-7 digits.ST Override Predesignation 1OXXX
Operator assistance KP-7 10 KP-II-7 digits-ST Override Predesignation 1OXXX or 10 digits or digits-ST3P
Coin KP-fl-7 Direct dialed 1OXXX or 10 digits KP-7 or 10 digits-ST digits-ST XP-STP KP-ll-7 digitSST Operator assistance 0- 1OXXX zero 10 ICP-7 cr10 digits-STP KP-1I-7 digits-ST Operator assistance lOW or digits
ST for interLATA calls SIP for intraLATA
6-148 Networks 1994 SR-TSV002275 BOC Notes on the LEC SignalIng Issue AprIl 1994
wink the ANT off-hook signal If time-out occurs waiting for the start-pulsing or request IC/INC no-circuit reorder announcement is connected If all trunks to the are busy
be seized for other reason reorder announcement is connected If trunk cannot any tone should be returned
coin-control Customer flashes are repeated to the operator-service facility Ringback from the facility operator-attached and operator-released signals sent operator-service should should also function as usual and normal operator-services disconnect procedures does wink off If an OSPS or TOPS office is be followed Operator hold continues as for the intraLATA to the interLATA it is transparent to the acting as an access tandem interLATA call
between an end Tables 6-28 and 6-29 show the various outpulsing formats for pulsing
There is similarity between Table 6-28 and office and operator-service facility great and Table 6-32 for OSPS or TOPS systems In both cases supercombined 0- be routed over coin and non-coin and and screened traffic can coin cannot be muted on the same trunk group as prepay single trunk group Post-pay coin
EAEO and an facility can always use the All trunk groups between an operator-service can also use pulsing supercombined format However the operator-service facility for the OSPS or TOPS formats analogous to those in Tables 6-33 6-34 and 6-35 systems and test call are when used for FGC if the BOC and IC agree International dialing
covered in Table 6-29
and 78 below are The three special ANT information digit pairs 110868 explained to handle calls from interLATA-restricted lines required for the operator-service facility calls to the facility serving These information digit pairs are sent only on operator-service Other used with OSS the carrier for which interLATA restriction applies ANT pairs 11
are as shown later in this section
of should be To aid the transition from the existing OSS both types signaling initially The of at the available at the end office and the operator-services system type signaling basis that the end offices can be is available on trunk so operator-services system group
converted office-by-office
Services Other information is available on OSS in FR-NWT-00027 OSSGR Operator
Systems Generic Requirements.20
6-149 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaling
Service Table 6-29 FGD Pulsing Format from End Office to Operator System International Calls and Test Calls
0- Coin 0- 01- Non-coIn and 0- Sereesied Traffic
International Calls
MultlfrequoiCy-PuISed AN Type of Customer Called Number Culfing Number5 Call Dials
Non-corn
Direct dialed CC NN KP CC NN-ST2P KP-ll-7 digits-ST Predesignated Carrier 011 011 CC NN KP CC NN-ST2P KP-II-7 digits-ST Oveiiide Predesignation lOlOOC
Operator assistance KP ST KP-II-7 digits-ST Predcsignated carrier 00 zero minus KP ST KP-ll-7 digits-ST Override Predesignation 1OXXX
Operator assistance NN KP CC NNST3P KP-l1-7 digits-ST Predesignated carrier 01 CC CC NN.ST3P KP-ll-7 digits-ST Override Predesignation 1OXXX 01 CC NN KP
Corn KP CC NN-ST KP-ll-7 digits-ST Direct dialed 10XO 011 CC NN
1OXXX 01 CC NN KP CC NN-STP KP-II.7 digits-STP Special toll handling
Typical Test Calls
Tester Muldfrequency-Pulsed AN Type of Number Call Dials Called Number Calling
lOX-ST Test lox KP XXXX.ST Test 958 XOCX KP-958 XXOC-ST Test 959 XXXX KP-959
information II Refer to Section 6.16A for the meaning of the digits
Special Signaling 6.15.5.3 Signaling for Calls Not Requiring Operator
calls not the special operator signaling The equal-access arrangement for requiring and NEAX-61E is 5ESS DMS-1O DMS-100F provided by OSS available in 1/lA ESS
switching systems
an access tandem to the IC/INC Calls from an EAEO can be routed directly or through while direct connection between an EAEO and the carrier Figure Figure 6-49 shows the calls from an EAEO to the carrier 6-50 shows an access tandem being used to route and tandem for single carrier as given EAEO can use both the direct arrangements shown in Figure 6-51
6-150 the LEC Networks 1994 SR-TSV-002275 BOC Notes on Signaling Issue ApilI 1994
TermInating LATA
Direct InterLATA EAEO EAEO Gonnecling DIG Trunk Group
Figure 6-49 Direct IC/INC Connection FGD
Terminating L.ATA OrigInating LATA
Connection FGD Figure 6-50 Tandem IC/INC
6-151 SR.TSV002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaling
Terminating LATA Originating LATA
IC/INC Connection FGD Figure 6-51 Combined Direct and Tandem
carrier IntraLATA interLATA and international calls can be muted to an appropriate
traffic be carried trunk if transmission All three types of can on single group for intraLATA thinks differ from requirements permit The transmission requirements intraLATA trunk those for tandem-connecting trunks In some cases segregated groups may be desirable
tandem to the All trunks from the EAEO to the access tandem and from the access tandem to the carrier IC/INC can be 1- or 2-way thinks Trunk groups from the access the traffic for that carrier Trunk from the EAEO to will necessarily carry only groups traffic from several ICsIINCs and for the BOC The generic access tandem can carry that FGD are shown in Table 6- programs for various manufacturers equipment support 27
sent from the EAEO Changes for There are major changes in the signaling format the IC/INC follow connection directly to
is 10 rather than ANT calling number information digits
second information digit is added to the ANT outpulsing
the called number with no controlled The ANT information is sent first followed by between the two of information outpulsing signal wink pieces
all The carrier sends an acknowledgment wink after receiving pulses
when call through Some of the additional changes in signaling format that occur passes
an access tandem are listed below
Two-stage outpulsing is used
and the access tandem It identifies the carrier The first stage of outpulsing is sent to
type of call
6-152 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
wink-start sent from the The second stage of outpulsing is controlled by signal IC/INC and repeated by the access tandem
from the end office the The second stage of outpulsmg is end-to-end outpulsed to
carrier
The acknowledgment wink is sent from the IC/INC and repeated by the access tandem
Answer supervision is received by the EAEO
Trunk Terminology Trunk terminology asshownin Figures 6-49and 6-50 is listed below
The trunk from an EAEO directly to an IC is Direct InterLATA Connecting DIC trunk
The trunk from an EAEO to an access tandem is tandem-connecting trunk
The trunk from an access tandem to an IC is Tandem InterLATA Connecting TIC trunL
be Dialing Plan The current dialing plan is based on the 1OXXX to expanded to
1O1XXXX carrier access code in lieu of presubscription where XXX serves to identify
for The is the specific carrier See Section dialing procedures dialing sequence be to 1OXXX Oil 7/10 digits where can any digit from The 7/10 digits dialed must conform to the North American Numbering Plan NANP
dial code followed the The NANP allows the calling party to the access immediately by
called partys telephone number without requiring second dial tone from the IC/INC establishes The EAEO receives all of the dialed digits determines the carrier and
connection to that carrier
Because the EAEO receives the customers complete dialing sequence directly any
DTMF requirement is eliminated As result either pushbutton or rotary-dial telephones can be used to access carrier
6.15.5.4 Signaling North American Dialing Plan
To minimize setup time on calls to an IC/INC an overlapped outpulsing format with the
connections via access tandem is used Details capability for two-stage outpulsing on an North American of the full-feature signaling format for the equal-access dialing plan
follow and are illustrated in Figures 6-52 through 6-55
Originating Direct Connection from EAEO to IC After the customer dials 1OXXX0/1NPANXX
The EAEO seizes an outgoing trunk to the appropriate IC
6-153 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Signaling
The carrier responds with wink-start signal
the 40 to 200 ms before After receiving the wink-start signal EAEO delays the EAEO KP ANT outpulsing If the carrier has requested AN outpulses 11 10 digits ST Otherwise it sends KP ST KP After the customer has completed dialing XXXX the EAEO outpulses
7/10 digits ST
has the as The IC returns an acknowledgment wink which same requirements
wink-start signal
from the far end The carrier returns tme called-party answer supervision
is in Table 6-30 Default timing for this signaling sequence
EAEO FGD Interface
After Customer Dials 1OXXX 0/1 NPA NXX
Seize
WInk
KPllANISTOrKPST
After Customer has Completed Dialing XXXX
KP 7/1OD ST
Acknowledge Wink
Answer Supervislon
True answer signal may or may not be provided
Direct Connection FGD Figure 6-52 Originating Signaling Sequence
6-154 L.EC Networks SR-TSV.002275 BOC Notes on the 1994 Signaling issu AprIl 1994
EAEO
AT
Interface
After Customer Dials 1OXX 0/1 NPA NXX
Seize
Wink
KPOZZXXXST
SeIze .4 Wink
Wink
KPllANIST0rKP-ST
After Customer has Completed Dialing CXX
KP 7/1 OD ST
Acknowledge Wink
10 Acknowledge Wink
.4 Answer SupeMsiont 11
12 Answer SupeMsion
and of wink to end office This wink Is timed in tandem for both time of arrival length
Th1s wink Is not timed in tandem
tTrue answer supervision may or may not be provided
Via Access Tandem FGD Figure 6-53 Originating Signaling Sequence
5.155 SR-TSV-002275 BOC Notes on the LEC NetworksI 994 issue April 1994 Signaling
EAEO FGD Interface
AT
Seize
Wink
KP7orlODST
Seize
Wink
KP 7D ST
Ringing
Answer
Answer Supervision
Answer 10 Supervision
True answer signal provided
Access Through an Access Tandem FGD Figure 6-54 Terminating Sequence
6-156 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SignalIng
EkO
FGD Interface
SeIze
Wink
KP7DST
Ringing
Answer
Answer Supervision
True answer signal provided
Figure 6-55 Terminating Sequence Direct From IC to EAEO FGD
Table 6-30 FGD Controlled-Outpulsing Default Timing
flme In Seconds an EAEO Will Walt
Type of Call After Seizure for After the flrst Stage of After Outpulsing Is from Wink-Start Outpulsing is Completed Completed an Wink Signal from the for Wink-Start Signal Acknowledgment CarrierorAT fromtheCarrlertoStart fromtheCarriertoShow
the Second Stage of that Pulsing has Been
Outpulsing Received from the EA.EO
nterLATA Not Applicable
Not via an AT
InterLATA 12
via an AT
International 20
6-157 BOC Notes on the LEC Networks 1994 SRTSV002275 issue April 1994 Signaling
in either direction between the BOC and IC Disconnect signaling can then be passed for customers colocated at an access The access tandem to carrier signaling sequence is the same tandem that is with the access tandem also serving an end-office function and described The as the signaling between an EAEO IC as previously AM defined in the Local Guide LERG.33 information digits II are Erchange Rowing
They are assigned as shown below
00Identified POTS Line no special treatment
01 Operator Number Identification ON1 Multiparty
02 AN Failure
06 Hotel/Motel Without Room Identification to obtain ON of the room
07 Special Operator Handling Coinless Hospital Inmate etc
with lox test 10 Not assignable conflicts code
12-19 Not assignable conflict with international outpulsing code
Identified Listed DN Sent 20 Automatically Outward-Dialing MOD
23 Coin or Non-coin Line Status Unknown
24 800 Service Call
27 Coin Call
number 30 Intercept blank for calls to an unassigned
31 Intercept trouble for lines in trouble-busy state
32Intercept regular for calls to recently changed numbers
34 Telco Operator Handled Call
40-49 Unrestricted Use locally determined by carrier
52 Outward WATS from 61 Cellular Service Type 1- for calls originating cellular carrier via Type trunks and forwarded to the 1C ANT
identifies only the cellular system
from cellular 62 Cellular Service Type 2- for calls originating the BOC to carrier via Type trunks and tandem-switched through
the IC ANI identifies the mobile directory number
for calls from 63 Cellular Service Roaming originating cellular carrier when muting traffic forwarded to cellular subscriber
70 Private Paystation
6-158 BOC Notes on the LEC Networks 1994 SR-TSV-002275 SIgnaling Issu April 1994
93 Access for Private Virtual Network types of service
95 Unassignable conflict with Test Codes 958 and 959
Originating Connection Via Access Tandem The two-stage overlapped calls via the access tandem to minimize call setup time outpulsing format is necessary on of to the Since the access tandem needs information in the first stage outpulsing identify
associated the first state of outpulsing must proper carrier and routing information include
Identification of this as an IC call
Identification of the carrier
described later in this section The type of call routing required as
from the to the access tandem has the format The first stage of outpulsing EAEO KP OZZ XXX ST where
one for each of call routing where OZZ spare tandem center codes type the is from to The initial identifies is the digit zero and any digit carrier of call as an interexchange call and ZZ identifies the maximum trunk four codes are available one for each of the maximum of four groups
between the access tandem and the carrier
XXX dialed or presubscribed ICILNC
an call via tandem after the customer dials The signaling sequence on IC an access 1OXXX 0/1 NPA NIXX is as follows
EAEO seizes trunk to access tandem
Access tandem responds with wink EAEOoutpulsesKPOZZXXXST
Access tandem seizes trunk to appropriate IC
IC responds with wink
the wink Access tandem cuts through the talking path and repeats
the the the call the BOC and carrier is identical to From this point on processing of by and other direct connection case except that all winks address digits signaling pass The EAEO should an off-hook of 100 to 500 ma through the access tandem recognize for this is in Table 6-29 as wink Default timing signaling sequence
when an connection via an access tandem There is signaling incompatibility originating and the other CCS such as SS7 The has one link using circuit-associated signaling using the second of circuit- incompatibility is caused by the fact that stage outpulsing using to the IC At there is no standard for this associated signaling is not repeated present will have to be changed before mixed signaling One or both of the signaling protocols
the carrier can receive the second stage of outpulsing
6-159 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Signaling
of the Terminating Termination of an IC call is straightforward operation consisting following
IC seizes trunk to EAEO or access tandem
EAEO or access tandem responds with wink
IC outpulses KP 7/10 digits ST
station and returns EAEO or access tandem completes the call to the appropriate
called-party answer supervision
calls to free lines Disconnect Answer supervision is returned on all calls including be in either direction between the BOC and the carrier signaling can then passed
6.15.5.5 Routing
IC call is from an EAEO and there is DIC trunk from Originating Calls If an placed If there is no available DIC that EAEOthe call will be routed first over DIC trunk the call be alternate-routed to an trunk and there are tandem-connecting trunks then can via the tandem On an IC EAEO tandem-connecting trunk group for completion access the station whose office is colocated with an access tandem call originating from used for calls from access tandem will route the call to the IC over the TIC mink group
subtending EAEOs
carrier from an EAEO or access tandem More than one trunk group may be provided to trunk to be used for different types of traffic The carrier can specify the particular group and calls on another for example calls may be placed on one group
the trunk to be selected from For calls routed from an EAEO via an access tandem group
in the first of from the the access tandem to the IC will be indicated stage outpulsing EAEO in the OZZ code
TIC trunk based the The access tandem can also route to different outgoing groups upon carrier from one EAEO can be routed on incoming trunk groups That is calls to EAEOs different outgoing TIC trunk groups than calls from other
rules for IC calls When call is routed using Routing for INC calls follows the same as
for traffic trunk is provided INC signaling the same capability splitting among groups will be for the The 1NX codes operator-assisted and nonoperator-assisted calls assigned be the whether the traffic direct or via an different types of traffic and will same goes access tandem and whether carrier is involved or not
call it will seize trunk Terminating Calls When an IC/INC terminates to LATA access tandem and outpulse via multifrequency signaling to the appropriate EAEO or orlOthotheaccesstandemor7dstotheEAEOt0C0mPletethet0the
the access tandem will be routed to the called called station Calls directed through In some network configurations the terminating station via the stations serving EAEO In functions of an access tandem and EAEO switching machine serves the combined discussed in this section these instances trunk treatment is provided as
6-160 th LEC Network 1994 SR-TSV-002275 BOC Notes on SIgnaling Issue Apr11 1994
wink Trunk Circuits All IC/INC trunks will be loop or EM multifrequency
facilities and interface signaling 2-wire or 4-wire facilities They generally use digital basis the carriers POT on Digital Signal level DS1 or DS3 Tandem-connecting trunks between the EAEO and the access tandem or DIC trunks between the EAEO and tandem and the the IC/INC are tandem-connecting grade Trunks between the access trunks are IC/INC are 4-wire intertandem grade with dB loss Switchable pad-type
if it combined access tandem and EAEO used at 2-wire analog access tandem serves functions
6.15.5.6 International Carriers
Points of Interconnection The carrier interconnection plan includes LATA access of features for INCs This arrangement is described below and utilizes the dialing plan
IDDD and currently the 1OXXX access prefix
interface with network or indirectly An INC desiring to serve LATA can LEC directly and interfaces with In this case the INC establishes Point of Presence POP in LATA tandem the LEC directly via an EAEO or an access
interface In this case the INC Figures 6-56 and 6-57 illustrate the indirect arrangement to/from these INC establishes gateway offices and an IC provides the domestic network interface to gateway offices The following sections describe typical LEC originating is the for IC the IC or INC for international calls The terminating interface same as
calls
NANP area from EAEOs are Dialing Plan Direct-dial calls to countries outside the is the code and NN is the dialed as 1OXXX 011 CC NN where CC country indicates that telephone number within the country The optional 1OXXX prefix iNC given customer line has dialed for or may be presubscribed to either an or integrated
carrier CC Operator assistance calls will be dialed as 1OXXX 01 NN
office will continue to use the same dialing Calls from any remaining non-equal-access
and routing plans as before 1984
Canada Puerto Rico the U.S The NANP is used in World Zone which includes the United States Caiibbean Islands Virgin Islands Bermuda and other
6-161 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling AprIl
ORIGINATING LATA
EAEO
AT Interface
EAEO
Figure 6-56 INC Interconnection Indirect Originating LATA FGD
TERMINATiNG LATA
EAEO
EAEO
indirect LATA FGD Figure 6-57 INC Interconnection Terminating
6-162 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 Signaling
international two- Routing and Signaling To minimize call setup time on calls
is used This is consistent with both the stage overlapped outpulsing format present in Access tandems handling of IDDD calls and the signaling for LATA access general the carrier ICs need need information in the first stage of outpillsing to identify proper to know which country code was dialed hence which INC and which gateway of that INC to connect to ICs and INCs also need to know the type of call routing required the information The first stage of outpulsing includes following
Identification of the call as an international call
Identification of the INC or integrated carrier that was dialed
Identification of the country code dialed
The type of call routing required for example operator
in The existing format of KP 011 CCC ST used first-stage IDDD signaling today
all this information Therefore new format has been designed cannot carry
KP 1NX XXX CCC ST where
of call 1NX International system routing codes one for each type routing
XXX Dialed or presubscribed carrier
CCC Country code padded with leading if needed
domestic the Consistent with the LATA-access signaling formats for calls signaling 6-58 and sequences on an international call are as follows Figures 6-59
Connection from EAEO Directly to IC Indirectly to INC After Customer Dials 1OXXX0l1 orOlCC
EAEO seizes trunk to appropriate IC
Carrier responds with wink EAEOoutpulsesKP1NXXXXCCCSTtOCarrier
The carrier can then either return wink to signify its readiness to receive more digits
the INC which then returns or process the connection through to appropriate gateway
wink to the originating end Therefore
IC returns wink to EAEO
EAEO outpulses KP 11 AM 3/10 digits ST
6-163 SR..TSV002275 BOC Notes on the LEC Networks 1994 Issue APIII 1994 Slgnalêng
After the customer has completed dialing NN EAEOoutpulsesKPCCNNST
IC returns an acknowledgment wink
IC returns called-party answer supervision
is in Table 6-30 Default timing for this signaling sequence
direction between the BOC and IC Disconnect signaling can then be passed in either
Connection via Access Tandem to IC Indirectly to INC After Customer Dials1OXXX01lorOlCC
EAEO seizes trunk to access tandem
Access tandem responds with wink EAEOoutsesKP1NXXXXCCCSTtOaCCeSStafldem
Access tandem seizes trunk to appropriate IC
IC responds with wink
carrier Access tandem outpulses KP 1NX XXX CCC ST to
IC or INC responds with wink
wink Access tandem cuts through the talking path and repeals the
EAEO outpulses KP 11 AN 3/10 digits ST
is identical the From this point on the processing of the call by the LEC and IC to other are direct-connection case except that all winks address digits and signaling passed through the access tandem
within the Connection Directly to INC When the INC establishes its own POP rather than via an IC Either LATA the INC can interconnect directly to the BOC stated direct or tandem access is possible Routing and signaling are exactly as
above with the IC being replaced by the INC
6-164 SR-TSV-002275 BOC Noes on the LEC Networks 1994
Issue April 1994 SIgnaling
After Customer Dials 1OXXX 011 or 01 CC
SeIze
Wink
KP1NXOOCCCST
WInk
KPilANIST0rKP-ST
After Customer has Completed Dialing NN KPCCNNST
Acknowledge Wink
Answer SupeMslon
True answer supervision may or may not be prvlded
at Direct Figure 6-58 International Call Originating Signaling Sequence Connection to INC or via IC FGD
6-165 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling Apr11
EAEO
After Customer Dials 0OO 011 or 01 CC
Seize
WInk
KP 1NX XXX CC ST
Seize
Wink
KP 1NX XXX CC ST
Wink
Wink
KPlIANISTorKP-ST
After Customer has Completed Dialing NN
10 KPCCNNST
Wink 11 Acknowledge
12 Acknowledge Wink
13 Answer SupeMslon
14 Answer Supervision
This wink is timed In tandem for both time of arrival and length of wink to end office
Thls wink Is not timed In tandem
True answer supervision may or may not be pnMded
at Connection Figure 6-59 International Call Originating Signaling Sequence to INC or via IC FGD
6-166 BOC Not. on the LEC Networks 1994 SR-TSV-002275 Signaling Issue April 1994
6.15.5.7 North American World Zone Calls
address outside the United States The processing of call to North American depends is or on whether the carrier designated by the originating customer an IC INC consolidated carrier North American World Zone calls are dialed 1OXXX
the is wherever it 10D The 1OXXX is the carrier identification code and required All World Zone calls to domestic and is normally required to signify distant NPA calls within the United States consolidated carriers are processed in the same manner as of the form Such calls are handled as international calls with first stage KP 1NXXXXO1RST
calls to The O1R identifies one of ten North American regions to distinguish among United but in World various regions based on NPAs outside the continental States INC Zone to assist in routing the call to an appropriate gateway
6.15.5.8 Supervision
is control of disconnect with The supervisory control for equal access calling-customer EAEO or as forced disconnect see Section 6.4.3 The typical switching system as an an access tandem will disconnect 10 to 11 seconds after the called party disconnects Table 6-8
domestic ICs The LECs use 1OXXX access dialing similar to that used for their 1OXXX codes to International Record Carriers IRCs are assigned own Routing the interLATA network selecting multiple IRC gateway locations is provided through by
is chosen the basis of the appropriate gateway office The gateway on originating
location and destination country code
features for IRCs This The carrier interconnection plan includes LATA-access of IDDD and has the 1OXXX access prefix arrangement uses the dialing plan currently
and TOPS Oftices 6.16 Special Tandem Signaling CAMA OSPS
record call details for customer billing CAMA CAMA OSPS and TOPS offices can and offices are to offices handle non-coin direct-dialed calls the OSPS TOPS arranged
and coin stations assistance handle long-distance calls from non-coin requiring operator offices and can also operate as CAMA
section reflect under FGC The arrangements discussed in this signaling provided feature and Section 6.15 shows the arrangements for all the groups
It it is from the end office The CAMA equipment records the called number as pulsed from the end office it has ANT An also records the calling number pulsed providing connected to the call to record the calling number if AN operator is temporarily end if the caller is on or multiparty line equipment is not available at the office 4-party is called failure at the end office This method of operation or if there is an identification
Operator Number Identification ONI
6-167 BOC Notss on the LEC Networks 1994 SR-TSV002275 issUe 1994 Signaling ApilI
from end office to or The primary information categories transmitted an CAMA OSPS
is TOPS office axe the called number and the calling number The called number sent on either an immediate-dial basis for dial-pulse calls or on wink-start basis for TOPS office multifrequency pulsing calls On thai-pulse calls the CAMA OSPS or goes off-hook toward the end office after the end of dialing has been recognized by ESS suitable timing interval On multifrequency pulsing calls to electronic CAMA 1/lA be returned the or 4ESS switching systems OSPS or TOPS offices the off-hook can to end office as soon as the ST pulse is recognized by the CAMA OSPS or TOPS system
As result the off-hook can arrive at the end office while the ST pulse is still being the sent This off-hook indication signals the end office to start outpulsing AN of the off-hook information There is no requirement for delay between the receipt start-dial by the end office and sending of the KP of the AN information However it is minimum of 50 between these two to the good practice to have delay ms signals permit
the first transients associated with the off-hook start-dial signal to dissipate before
6.5.6 for information similar situation multifrequency pulse is sent See Section on with the on-hook start-dial signal used to send address information Multifrequency pulsing is always used to send the AN information
office and the end and The pulsing characteristics between the CAMA OSPS or TOPS for distant offices for the called and calling number are the same as the characteristics normal pulsing on the network See Section 6.6 and 6.12.1 through 6.12.3 However from those in network for the ANT case the signaling formats are somewhat different and numbers are covered in Section pulsing The signaling formats for the called calling 6.16.4
toward the On ON calls the CAMA OSPS or TOPS incoming trunk goes off-hook end office in the same manner as described above after the called number has been received
office that the call is This off-hook signal indicates to the originating being processed
for either ANT or an call it will satisfactorily Once the trunk has gone off-hook an ON coin remain off-hook for the rest of the call except for wink signals associated with control and re-ring
This The trunk may be forced off-hook toward the end office for maintenance reasons off-hook should make the end-office end of the trunk busy This feature is known as
end office will reverse make-busy There is no guarantee however that the always office Certain receive an off-hook on every call to CAMA or operator-services calling not result in an sequences such as permanent signal partial dial or vacant code may off-hook toward the end office
in Section 6.4.3 Control of disconnect in CAMA or operator-services offices is covered
nBOcendofficesthessdonotreCozetherflOfaflOff.hOOkSi5flniWhiletheSTPUlSClS
and after of the ST For being sent because they are blind to the supervisoy state during outpulsing pulse Section 63.7 information concerning unexpected stops sec
6-168 SR.TSV-002275 BOC Notes on the LEC Networks 1994
IssUe AprIl 1994 Slgnalln9
6.16.1 Signaling to CAMA
6.16.1.1 Types of Switching Systems used as CAMA Offices
The following ATT Northern Telecom and NEC switching systems may be arranged as CAMA serving offices 1/lA ESS 4ESS and 5ESS switching systems OSPS DMS
10 and DMS-200 switching systems and NEAX-61E
6.16.1.2 Called-Number Outpulsing Format in CAMA
formats These differences CAMA offices have three called-number outpulsing are important because they impose different permanent signal and partial dial timing requirements on the connected switching systems The CAMA systems do not always outpulse all the called number digits at one time Outpulsing can start
As soon as sufficient digits are available to advance the call toward its destination
When the first digit of the calling number is received
received When all digits of the calling number are
6.16.1.3 Overlap Outpulsing from CAMA
Overlap outpulsing is method of outpulsing developed to minimize post-dialing delay
With overlap outpulsing the call is advanced toward its destination as soon as sufficient address information is available Once call is advanced each succeeding digit is sent
the the forward as soon as it is received Thus with overlap pulsing timing of pulses from the CAMA office can be maintained to the end office serving the called line
6.16.1.4 CAMA Outpulsing Formats
These are the CAMA outpulsing formats
Nonimmediate-start multifrequency or dial-pulse does not begin outpulsing until the
is received This format is used for calls from first digit of the calling number 1/lA ESS switching systems and OSPS CAMA or TOPS CAMA offices
The 4ESS system does not outpulse the called number until the complete calling
number is recorded
for line The DMS-100 system provides the ability for overlap outpulsing to
trunk/trunk to trunk
for The DMS-10 system can provide optional overlap outpulsing dial-pulse signaling on CAMA OSPS and Extended Area Service EAS routes and for multifrequency mutes signaling on equal-access and operator-service
6-169 SR.TSV002275 BOC Not. on the L.EC Networks 1994 issue April 1994 Signaling
determine the internal route to trunk group Once enough digits have been collected to will start usually all but the last digits outpulsing
6.16.1.5 CAMA ANI Pulsing Format
is KP -7 or 10 digits ST The CAMA AN pulsing format with controlled outpulsing ST for the number The for the called number followed by KP 17 digitS cafling in Table 6-36 This is the meanings of the single AN digits are given procedure but Identification 01 and Identification Failure IF calls preferred method on Operator not available and the ST is optional calling number digits are
6.16.1.6 CAMA Permanent Signal and Partial Dial Timing
on trunks is to 10 The end office or tandem permanent signal and partial-dial timing and 20 to 30 seconds overall permanent- seconds for permanent signal or partial-dial of 16 to 21 seconds has been used on immediate-start signal or partial-dial timing tandems in the network the immediate-start pulsing In the absence of crossbar These times do not affect recommendation can be reconsidered and possibly dropped
dial in offices the permanent signal and partial timing succeeding
6.16.2 TIme from Request for ANI to ANI FaIlure In CAMA
for ANT until the call is offered to an The following shows the time intervals from request not received operator because AN information was
1/lA ESS switching system 1.0 to 8.0 seconds
2/2B ESS switching system not applicable
OSPS seconds
seconds from 4ESS system 8.0 seconds to receive Information digit 5.0 digit
to all remaining digits
5ESS system 11.0 seconds
office from to 155 seconds with 128-ms DMS-10 system software adjustable per
step
trunk from to 30 seconds DMS-200 system software adjustable per group
6.16.3 CAMA Transfer
office the function can be CAMA OSPS or TOPS The operators who perform ON the ON function for separate CAMA office operators When these operators perform With this two voice- the arrangement is known as CAMA transfer arrangement office between the CAMA office and the OSPS or TOPS frequency circuits are required
6-170 th L.EC Networks 1994 SR-TSV-002275 BOC Notss on SignalIng Issue Apr11 1994
tones are received from the CAMA the talking path over which call-defining zip and the office and over which the operator can converse with the customer keypulse number are returned to the CAMA office path over which multifrequency calling signals of as keyed by the operator Table 6-31 indicates the exchange sequence supervisory
these circuits between the CAMA office and the OSPS or TOPS signals passed over the various conditions for office for loop and EM signaling The following explains
each sequence
from the Out-of-Service The OSPS office is not prepared to accept traffic CAMA this state office and will ignore seizures from it The CAMA office should recognize service and not request
receive traffic from Position Occupied The OSPS or TOPS office is prepared to
the CAMA office
Position Seizure The CAMA office requests service from the OSPS or TOPS
office
the OSPS TOPS office reacts to the Position Busy After 700- to 900-ms delay or the call seizure by the CAMA office This signals it to send identity signals
office order tone is sent the CAMA Call Identity Signals 1- or 2-pulse signal by for number is as the result of an ANI failure or indicating whether the calling required
call that is normally operator identified ON1
indicate Sender Attached sender-attached signal is sent by the CAMA office to
receive number that it is prepared to multifrequency calling signals
the or TOPS office Position Attached position-attached signal is sent by OSPS the mink and to serve the to indicate when an operator is actually attached to ready when the customer Position attached may occur before sender attached operator- office should be insensitive to this services office is lightly loaded The CAMA
sequence
tones are sent to the Multifrequency Calling Number Signals Multifrequency
CAMA office identifying the calling number
number as Reorder If the CAMA office cannot recognize the calling signals
The will this signal and meaningful it will send reorder signal operator recognize BACK in OSPS or TOPS offices which should the key the reset signal KP prepare The will the CAMA office to receive the calling number again operator again key Should the number remain unacceptable to the CAMA office the calling number to the or TOPS office If the operator decides reorder signal will again be sent OSPS the sends the that continuing the process will not salvage the call operator position office disconnect signal to the CAMA
is to the CAMA office it sends CAMA Release If the calling number acceptable the office the release signal to OSPS or TOPS
OSPS TOPS office will to the The OSPS or TOPS Releases The or respond condition CAMA release by returning to the position-occupied
6-171 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Signaling
ONI and Table 6-31 Supervisory Signal Exchange Between Operator Providing CAMA
Loop Signit1in
OSPS or TOPS CAMA
Sequence Talk KP Talk KP State System Signal
Out of ServIce On-Hook On-Hook
On-Hook Not5eqiing On-Hook
Po0n On-Hook Off-Hook On-Hook On-Hook Occupied
CAMA On-Hook Off-Hook On-Hook Off-Hook
On-Hook On-Hook On-Hook Off-Hook Position Busy Cy T2
Sender 4.4n On-Hook Off-Hook Off-Hook
OSPS Position Off-Hook On-Hook Off-Hook Off-Hook
TOPS Alt_ached
MF OSPS MFCaJItng TOPS No Signals SlgnaIs
Off-Hook On-Hook On-Hook Off-Hook MA letrtier
or oss Raset TOPS Reseti TonV
CAMA Off-Hook On-Hook On-Hook On-Hook
OSPS OSPS or TOPS On-Hook Off-Hook On-Hook On-Hook TOPS Release
00100k OSPS Position TOPS Disconnect
Continued on next page
6-172 the LEC Networks 1994 SR-TSV-002275 BOC Noes on SIgnaling issue April 1994
and Table 6-31 Supervisory Signal Exchange Between Operator Providing ON CAMA Continued
EM Signaling
OSPS or TOPS CAMA Sequen Talk KP Talk KP State System Signal
Out of SeMce On-Hook Off-Hook
OSPS Position On-Hook On-Hook On-Hook On-Hook TOPS Occupsed
CAMA --ook On-Hook Off-Hook On-Hook
OSPS On-Hock Off-Hook Off-Hook On-Hook BUSY
Cae Tos
CAMA Sender On-Hook Off-Hook Off-Hook Off-Hock Ansthed
OSPS Position ff4-4of ff414 Off-Hook Off-Hook TOPS Attached
MF OSPS MF Calling TOPS No Signals Signals
CAMA ieLert Off-Hook Off-Hook Off-Hook On-I-look
tori Reset OSPS Tone TOPS Reset .J
Off-Hook Off-Hook On-Hook On-Hook CAMA Released
OSPS OSPS orTOPS On-Hook On-Hook On-Hock On-Hook TOPS Release
Off -Hook OSPS Position TOPS Disconnect lOOms On-Hook
Call Identity Signal Zip Tones 900C Tone 480 Hz ala minimum of 0.062-V mis -24 dBm bddglng 1.380 Tone Timing ANI Failure 0.420 to ONI Tones 0.050 to 0.175 Tone
0050 to 0.175 SIlence
0.050 to 0.175 Tone
Reset Tone 700 and 1700 Hz ST3P
6-173 BOC Notes on the LEC Networke 1994 SR-TSV-002275 issue 1994 Signaling April
the OSPS TOPS Position Disconnect At any point in the signaling sequence or The office can terminate the call by sending the position-disconnect signal CAMA
office will respond with CAMA release
6.16.4 Operator Office Outpulsing Formats and Trunking Plans
have of When interfacing with end offices the OSPS or TOPS offices can variety in the sections trunking plans and outpulsing formats as discussed following However
what the customer dials for the various types of calls is not influenced by the trunking
format used the end office plan or outpulsing by
6.16.4.1 Outpulsing Format
The end office identifies the type of call to operator-services offices by using four
different multifrequency start signals On calls where the end office uses multifrequency
is with the called number pulsing for the called number the appropriate start signal sent with On calls where the end office uses dial pulsing the appropriate start signal is sent
the ANT information In addition timing is used to identify the type of call For
is dialed toll example when it is desired to reach an operator call When special
handling is desired for example collect person-to-person credit card etc call for followed by the called number is dialed The and 0-i- calls use the same ST pulse
identification As result other means have to be used to separate these two categories
of calls In customer-originated calls OSPS and TOPS offices consider dialing pause
of over to seconds after dialing to be 0- call In multifrequency pulsing calls
the but with KP followed by start signal of STP or ST3P depending on trunking plan
no called number is outpulsed to identify call
of dial- OSPS or TOPS offices currently initiate timing following the receipt leading
if additional follow is the pulse digit to determine digits Timing performed by
and is not terminated until operator-services OSPS or TOPS processor complete digit the consisting of two to nine pulses is registered by dial-pulse receiver and reported to seconds for of This processor The time interval is to receipt complete digit change will allow the customer minimum of approximately seconds to begin while the customer to wait no than seconds dialing second digit requiring longer office returns the When it is determined that the call is call the operator-services
off-hook ANT request signal
seconds The TOPS system is adjustable from to 30
6-174 SR-TSV..002215 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SignalIng
6.16.4.2 Trunking Plans
It The OSPS or TOPS office can have variety of trunking plans can
The Combine all coin and non-coin traffic on one supercombined trunk group
pulsing format for this arrangement with ANT is shown in Table 6-32
traffic another The Combine all coin traffic on one trunk group and all non-coin on 6-33 pulsing format for this arrangement with ANT is shown in Table
Combine all coin traffic on one trunk group and all non-coin traffic on
another The pulsing format for this arrangement with ANT is shown in Table 6-34
The coin and non-coin traffic would be handled on two additional trunk groups
also shown in Table 6-34
non-coin traffic Use six individual trunk groups for coin and Table 6-34 and The pulsing format for this arrangement with AN is shown in without ANT in Table 6-35
the In each case where more than one type of traffic is carried on single trunk group ST or information type of call is identified by distinctive multifrequency digits digits the transmitted from the end office with the called/calling number For dial-pulsing calls identifying ST pulse is associated with the AM information For multifrequency pulsing information For both calls the identifying ST pulse is associated with the address
is with the information multifrequency and dial-pulsing calls the information digit ANT
is used with each call to indicate whether To separate traffic different information digit
and also whether it it has been subject to local service observing was processed by identification failure automatic identification operator identification or procedures
Tables 6-32 through 6-35 show this information Figure 6-60 shows typical outpulsing format for multifrequency address signaling
6-175 BOC Notes cii the LEC Networks 1994 SR-TSV002275 1994 SignalIng Issue April
to OSPS or Table 6-32 Pulsing Format from Non-conforming End Office an TOPS Office with ANI Supercombined Coin and Non-coin Trunk Group
0- Coin 0- Non-coin and 0- 1-i- Screened Traffic
Multifrequency Pulsing
Type of Customer Multifrequency-Pulsed AM
Call Dials Called Number Calling Number
Non-coin
Direct dialed or 10 digits KP-7 or 10 digits-ST2P KP-I-7 digits-ST
KP-ST3P KP-I-7 digits-ST Operator assistance zero 10 KP-7 or 10 KP-I-7 digits-ST Special toll 07 or digitS digits-ST3P
Coin
Direct dialed or 10 digits KP-7 or 10 digits-ST KP-I-7 digits-ST KP-STP KP-I-7 Operator assistance zero digits-ST KP-7 10 KP-I-7 Special toll 07 or 10 digits or digits-STP digits-ST
Dial Pulsing
Type of Customer Dial-Pulsed AM
Call Dials Called Number Calling Number
Non-coin
Direct dialed or 10 digits or 10 digits KP-I-7 digits-ST2P
Seizure no KP-I-7 Operator assistance zero digits digits-ST3P 10 10 KP-I-7 digits-ST3P Special toll 07 or digits or digits
Coin
Direct dialed or 10 digits or 10 digits KP-I-7 digits-ST
Seizure no KP-I-7 digits-STP Operator assistance zero digits 10 or 10 KP-I-7 digits-STP Special toll 07 or digits digits
Note See Table 6-36 for meaning of information digit
6-176 SR-TSV-002275 BOC Notes on the I.EC Networks 1994
Issue AprIl 1994 SignalIng
OSPS TOPS Table 6-33 Pulsing Format Non-conforming End Office to or Office with ANI Combined Coin or Combined Non-coin Trunk Group
Combined Coin
0- Coin
Combined Non-coin
Non-coin
0- Post-pay coin
0-0 1Saeenedtxafflc
0- Non-coin combined with
00 14-post-pay coin and/or 0- saeened traffic
Multifrequency Pulsing
Type of Customer Mukifrequency-Pulsed AM
Call Dials Called Number Calling Number
KP-I-7 Direct dialed or 10 digits KP-7 or 10 digits-ST digits-ST
Operator assistance zero KP-STP KP-I-7 digits-ST
KP-7 10 KP-I-7 Special toll or 10 digits or digits-STP digits-ST
Pulsing
Type of Customer Dial-Pulsed ANT
Call Dials Called Number Calling Number
Directdialed 1lorlodigits orlOdigits KP-I-7digits-ST
Operator assistance zero Seizure-no digits KP-I-7 digits-STP ICP-I-7 Special toll or 10 digits or 10 digits digits-STP
Note See Table 6-36 for meaning of information digit
6-177 SOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue AprIl 1994 Signaling
Table 6-34 Pulsing Format Non-conforming End Office to OSPS or TOPS Office with ANI
Individual 0- Corn
0- Non-coin
Post-pay coin
0- Screened traffic
Combined
0- Coin
04- Non-coin
Post-pay coin
Screened traffic
0- 04-Non-coin combined with
0- 04-post-pay coin and/or
Gi- screened traffic
Non-coin combined with
post-pay coin and/or
screened traffic
Multifrequency Pulahig
ANT Type of Customer Multifrequency-Pulsed
Call Dials Called Number Calling Number
KP-l-7 Direct dialed or 10 digits KP-7 or 10 digits-ST digits-ST
KP-I-7 Operator assistance zero KP-ST digits-ST KP-I-7 zero Seizure-no digits digits-ST
ICP-7 10 KP-I-7 Special toll or 10 digits or digits-ST digits-ST
DIM Pulsing
ANT Type of Customer Dial-Pulsed
Call Dials Called Number Calling Number
10 10 KP-I-7 digits-ST Direct dialed or digits or digits
Operator assistance zero Seizure-no digits KP-I-7 digits-ST
10 KP-I-7 digits-ST Special toIl or 10 digits or digits
Note Sec Table 6-36 for meaning of information digit
6-118 BOC Notss on ths LEC N.twork 1994 SR-TSV-002275 Signaling issu Apr11 1994
End Office to an OSPS or TOPS Table 6-35 Pulsing Format Non-conforming Office without ANI
Individual Trunk Groups
0- Os- Corn
0- 04- Non-coin
0- Post-pay coin
0- Screened traffic
Combined Trunk Groups
0- Os- Coin
0- Os- Non-coin
0- Os-Post-pay coin
0- Os- Non-coin and
identificasion Os- post-pay coin with service tone
Multifrequency Pulsing
Type of Customer Multifiuquency-Pulsed Number Call Dials Called
Dircctdialed l7orlodigits KP-7orlodigits-ST
Seizure-no digits Operator assistance zero zero KP-ST
or 10 KP-7 or 10 digits.ST Special toll digits
Dial Pulsing
Dial-Pulsed Type of Customer Called Number Call Dials
Directdialed 17orlodigits 7orlodigits
Seizure-no digits Operator assistance zero 7orl0digits Specialtoll 0-4-7orl0digits
ST will be ST indicates that any of the usable signals accepted
is associated with the called number each of the above Because the identifying ST pulse be ANI from the end office The only multifrequency pulsing formats can used without format without could be used is when usable situation under which the dial-pulsing AN of service an individual trunk group is used for each type
6.16.5 Information Digits
6-35 used for calls Tables 6-32 through Information digits are operator-services system
cover the operator-services system application
and TOPS offices Some The information in this section covers operation with OSPS of as non-BOC exchange carriers will continue to use this mode operation indefinitely dual information digit format is will some switching systems in the BOCs However
associated with equal access
6-179 SR-TSV.002275 BOC Notes on the LEC NetworksI 994 Issue AprIl 1994 Signaling
CAMA InformationdigitsO and5areusedwith the same meaningrnthe and nonobserved calls while digits 34 OSPS and TOPS systems Digits identify will continue to calls These information digits see Table 6-36 and identify observed are now standard be used However the information digits for equal access
Table 6-36 Information Digit
Service Nonobserved Observed
Automatic Identification Al
Operator Identified 01
Identification Failure IF
Hotel/Motel
Special Screening for example Charge-a-Call
6- services are shown in Tables 6-32 through Information digits and OSPS or TOPS 35
6.17 Operator-Services Oftice Coin Control Signaling
methods of coin control have evolved to meet changing Over the years several different the multiwink and expanded needs In addition to coin collect coin return and ringback the coin control the of the battery applied to inband methods provide signals to polarity office telephone by the end
of coin control used from the OSPS or TOPS There are three different methods signaling multiwink and Expanded Inband Signaling system to the end office They are inband locations and EIS coin control All can be used from host or remote operating company All three either or carrier facilities can be used with EM lead signaling on physical
control be used with 2-wire physical facilities employing loop types of coin can Card Service multiwink and EIS coin control signaling However with Calling only control without station set modifications typical provide DTMF pad and totalizer in 6-60 office is shown Figure outpulsing format for end to operator-services system
in TR-TSY-000528 Coin and Charge-a-Call Coin-control signaling is covered
6-180 SR-TSV002275 BOC Notes on the LEC Networks 1994
Issue Apr11 1994 SignalIng
After Customer has Completed DIalIng 0/1 NPA NXX XXO OR zero
SeIze Off-Hook
Wink
KR NRA NXX OOX ST SW ST2P ST3P or KR SW ST3P
Off-Hook
KPl7DIgItANISTSTP
Figure 6-60 Originating Signaling Sequence
6.17.1 Inband Coin Control
6.17.1.1 Signals
Inband coin control uses multifrequency signals to control coins and ring back the coin
station as covered under collect return and ringback in Table 6-22
An on-hook wink off- on- off-hook of 70 to 130 ms is sent 50 to 150 ms in duration
when received from the operator-services system to alert the end office to prepare
receiver for the multifrequency signal that begins 95 to 195 ms after the end of the wink
The multifrequency signal will persist for approximately second for collect and return
and seconds for ringback
6.17.1.2 Ringback Protocol
Ringback protocol is described in Section 6.17.3 It is used in DMS-100 5ESS and
EWSD switching systems
6-181 SR.TSV.002275 BOC Notes on the LEC Network 1994 issue Apr11 1994 Signaling
6.17.2 Multlwink Coin Control
sent from an Multi Wink coin control uses multiple on-hook wink signals operator- DMS-100F and EWSD services office to an end office It is used in 5ESS DMS-10 coin coin and signals this signaling systems In addition to collect return ringback called and format provides signals operator-attached operator-released
the used with dial-tone-first coin telephones to instruct The operator-attached signal is to the toll end office to change the mode of the coin totalizer or coin signaling priority the coin Section 6.18.1.1 It is mode by application of positive battery to telephone see office because the not sent the first time coin call is forwarded to the OSPS or TOPS
coin call to the office in the end office is expected to connect operator-services is before each condition the operator-attached signal sent operator-attached However office attachment coin deposit The operator- subsequent operator-services requiring the coin restores the coin totalizer released signal negative battery supplied to telephone and enables the DTMP pad on certain coin or coin signaling priority to the local mode whenever the office telephones The operator-released signal is sent operator-services to the coin It is releases from connection having positive battery applied telephone coin call on dial-tone-first trunk when the also sent upon initial connection to trunk provides for Calling Card Service
6.17.2.1 Signals
series of one to five on-hook The multiwink signaling format employs supervisory trunks shown in winks from the OSPS or TOPS office to the end office outgoing as
Table 6-37
Table 6-37 Multiwink Signals and their Functions
Office Number of Subsequent OSPS or End On-Hook TOPS Guard Interval Work Time Winks Function Minimum Maximum
380 ms Operator-Released 500 ms 380ms Operator-Attached 500 ms
880 Coin Collect 1.1 seconds ms
Coin Return 1.1 seconds 880ms
2.1 seconds Ringback 2.4 seconds
6-182 the LEC Networks 1994 SR-TSV002275 BOC Notes on SignalIng Issue AprIl 1994
70 to 130 ms and The wink on-hook intervals as sent by the operator-services office are To allow for distortion the end the wink off-hook intervals are 95 to 150 ms pulse with on-hook intervals from 50 to office trunk circuit should be capable of operating when received 150 ms spaced from 75 to 185 ms apart
office will allow time for the end office At the end of wink signal the operator-services of the before sending new signal The to complete detection and application signal office and the maximum minimum interval after sending signal by the operator-services shown in Table 6-37 time in which the end office must detect and apply the signal are
6.17.2.2 Ringback Protocol
in Section 6.17.3 The ringback protocol is described
6.17.3 EIS Coin Control
wink to alert the end As with inband coin control EIS coin control employs an on-hook
It is used in 1/lA ESS 2/2B ESS 5ESS office that multifrequency tones will be sent is extended to DMS-100F and EWSD switching systems With EIS the wink produce when In addition an on-hook of between 325 and 425 ms 300 and 450 ms received of the tones the interval between the end of the wink signal and the start multifrequency
770 and 850 while the duration of the tones is reduced to is lengthened to between ms between 480 and 700 ms
6.17.3.1 Signals
and OSPS and TOPS offices are able to work with EIS EIS provides operator-attached in EIS coin station as does multiwink coin control However operator-released signals Service is call on trunk providing Calling Card initiating or nonchargeable the the office with negative battery applied to initially connected to operator-services
calls are initially connected with station As with the other signaling methods the The signal is sent whenever operator- positive battery applied operator-attached and the signal is sent services office is connected for coin deposit operator-released
office is released from connection having positive whenever the operator-services is combined the coin station signal not available with multiwink battery applied to which causes the end office to collect coin-collect and operator-released This signal the coin station is currently used for interim coins and then apply negative battery to
overtime collections on calls still in the talking state
600 the and operator-attached signals are The guard intervals following operator-released seconds ms Guard intervals following the other signals are
6-183 SR-TSV-002275 BOC Notes on the L.EC Networks 1994 Issue AprIl 1994 Signaling
6.17.3.2 Ringback Protocol
The OSPS or TOPS office sends one ringback signal The end office applies standard toward the ringing seconds on seconds oft to the station and audible ring the office release is operator-services office until the station answers or operator-services times for 30 to 36 seconds for answer If received The operator-services office waiting coin return before answer is not received it releases back The end office performs
is received and coin-control sent release- releasing the coin station if answer signal back will not occur until at least 300 ms after completion of the signal
6.18 Operator-Services Office Signaling Sequences for Automatic Coin Toll Service and Calling Card Service
offices make use of The ACTS and Calling Card Service features of the operator-services coin control described in Section 6.17 The the additional signals The signals for are described in this section In some cases sequences of these signals and other signals are interval the end office time to two back-to-back signals spaced by guard to give between coin control respond are used Guard intervals are also necessary signals The machine-generated announcements and certain other supervisory signals following information these more sections supply the signaling protocol and timing on complex
interfaces
Section 6.18.1 describes the However before going into ACTS and Calling Card Service in use in DTMF and coin totalizer control in the two types of coin telephones common Coin- the BOCs and Section 6.18.2 describes the interface before these features existed
covered in TR-TSY-000528 Coin and Charge-a control signaling and charge-a-call is
Call
6.18.1 Coin Telephone DTMF Pad and Coin Totalizer Control
in service in the networks used for There are two different types of coin telephones BOC
is dial-tone-first These are prepaid coin service The older is coin-first the newer discussed in the following sections
6.18.1.1 Coin-First
-48 on the and These coin telephones use negative battery supply usually ring for when range-extenders are ground on the tip but possibly other voltages example on the used from the end office They do not require positive battery supply 48 is disabled unless and the If with DTMF the DTMF pad ring ground on tip equipped been made When the is collected or an initial deposit equal to the local rate has deposit called coin retention has been provided for returned the pad is again disabled feature and is for Calling Card DTMF pad enablement with coin-first telephones required Service
6-184 Networks 1994 SR-TSV002275 BOC Notes on the LEC Signaling issue AprIl 1994
6.18.1.2 Dial-Tone-First
enabled and These corn telephones initially have the DTMF pad negative battery
the battery places the coin supplied as with the coin-first telephones However negative until totalizer in the C-series sets in the local mode that is the readout does not occur an
in coin amount equal to the initial rate is deposited This can result composite signals In the D-series the which may not be recognized by operators or ACTS sets negative the coin during coin battery gives the pad priority over signals Thus pad operation at the office deposit may result in coin signaling errors operator-services
is needed from the end office when coin deposit is requested positive battery supply the coin totalizer in by the operator-services office The positive battery supply changes an the C-series sets to the toll mode so that coin deposits of any denomination cause
immediate readout which can be detected by an operator or by ACTS equipment In the interference D-series sets it gives priority to the coin deposits preventing DTMF pad
also disables the on all but of thai-tone-first coin The positive battery supply pad D-type the coin to ACTS was desirable to telephones Disabling pad during deposit prior of the with ACTS the coin tone prevent simulation coin tones with pad However will to so the receivers used at operator-services offices not respond DTMF signals pad- of reference if battery were disabling function is no longer necessary By way positive coin-first the DTMF and the coin supplied to an early-model A-series telephone pad
totalizer would fail to function
6.18.2 Interface Prior to Calling Card ServIce
Card 6.18.2.1 Coin-First Operator-Services System Interface prior to Calling Service Introduction
interface is as follows The coin-first operator-services system
Coin collect coin return and ringback are the only coin-control signals required
used trunks coin traffic Multiwink and Inband coin control is generally on handling and EIS can be used but the additional signals operator-attached operator-released not functional EIS coin-collect/operator-released are
with totalizer the coin denomination tones or Single-slot coin telephones sending be used the traditional three-slot coin telephones with the bell and gong can since the bell However with the latter an operator must supervise the corn deposit with and gong are not compatible ACTS
retained an end office in Originally the initial deposit was However operating the before the coin non-Calling Card Service environment returns deposit connecting
call to an operator-services office
the coin is The end office The end office battery supply to telephone negative may the of the call but interchange the voltage on tip and ring of the line during course
is not used positive battery supply
6-185 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Signaling
local rate When the DTMF pad enablement depends upon the deposit of the initial
in the the is enabled Collection or return of the initial rate is present hopper pad coins disables the pad
to 6.18.2.2 Dial-Tone-First Operator-Services System Interface prior Calling Card Service Introduction
in the The introduction of dial-tone-first coin telephones required one major change
coin totalizer used in most dial-tone-first operator-services interface The single-slot
from the end office to it in the toll telephones requires positive battery supply place immediate readout The D-series requires positive mode so that coin deposits cause an over DTMF The following describes the battery to give coin signals priority signals
dial-tone-first operator-services interface
Jnband is the same Any of the coin-control signaling methods can be used operation If multiwink EIS is used as with coin-first see first bullet in previous section or
used control the additional signals may be to battery polarity
The coin telephones are single slot or multislot same as coin-first Early production be used with dial-tone-first nor can they be used single-slot sets the A-series cannot and dial-tone-first because the as coin-first in an end office serving both coin-first
disables the set positive battery
the end office as Any initial deposit is returned by same coin-first
the coin station fromthe end office is normal for dial- Negative battery supply to of call tone-first coin telephones in the origination and dialing stages However trunk the when the station is connected through the outgoing to operator-services with The office the end office replaces the negative battery supply positive positive mode in coin supply changes the coin totalizer or signaling priority single-slot remains connected until the call telephones as mentioned above This positive supply office unless multiwink or EIS is provided is disconnected by the operator-services
with the additional signals functional to control battery polarity
call an The DTMF pads in some coin telephones are disabled during any through in which has battery applied continuously The pad operator-services office positive Pad enablement does not the D-series set is not affected by battery polarity depend
the on the presence of coins in hopper
6.18.3 ACTS and Operator-ServIces System Interface
offices automatic ACTS provides coin tone detectors in the operator-services permitting The for either of coin service remain coin deposit counting to be used requirements type coin the same except that coin telephones must provide dual-frequency deposit signals simultaneous tones of 1700 and 2200 Hz or 1537 and These signals must consist of two -24.8 dBm and dBm into 600 fl each 2200 Hz at power level between office The tone are changed each frequency as received by the operator-services pairs
6-186 SR-TSV-002215 BOC Notes on the L.EC Networks 1994
Issue Apr11 1994 SignalIng
timethecoinboxiscollected Aminimumof6 msoftoneisneededtorecognizeacom signal After detection the coin detectors should bridge no-tone intervals of 10 ins in the coin tone
160-ms and must be followed The tone burst representing nickel must be 35- to long by
silent interval of at least 160 ins before another coin signal is detected dime is represented by two bursts 35- to 160-ms long spaced by 25 to 160 ins The silent
is denoted five bursts The interval after dime signal must exceed 60 ins quarter by
fourth are 20 to 60 ms first and fifth may be 20- to 100-ms long The second third and 20 60 The first and second may be spaced by 2Oto 110 ms the rem2ining by to ms
is followed 60-ms silent interval The times The end of quarter sequence bya given above are shown graphically in Figure 6-61
The coin-tone detectors will not recognize DTMF signals as coin deposit Therefore
DTMF pad disablement is not necessary when ACTS is used
Here are the default values for various ACTS parameters
is 5.5 Initial Timeout Timeout for initial ACTS contacts Default value seconds
Charge Due Timeout Timeout for charge-due contacts Default value is seconds
Initial Announcement Delay Amount of time between initial announcements
Default value is seconds
Charge Due Announcement Delay Amount Of time between charge-due announcements Default value is seconds
of time between two TAC Time and Charge AC Announcement Delay Amount announcements Default value is seconds
Ring Back Time The amount of time that ACTS should ring back the telephone on
value is 30 calling-party disconnect with charges due Default second
Ring Back Answer Delay Amount of delay needed for the customer to bring the receiver to his/her ear on ringback answer Default value is seconds
Collect Time Maximum amount of coin collection time allowed on recalled
ACTS call Default value is 32 seconds
6-187 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaling
Nickel l6Oms __15.160mS
DIme 35-160ms 25-160ms 35-lSOms 60 me
20- 20- 20- 20 60 ms 20- 20- 20- 20- T2o- 6Oms 60m8 6Oms1lOOmS ouarter_jiooms llOmsj6Oms 60ms160mS ___
Figure 6-61 Coin Deposit Signals
Interface 6.18.4 CallIng Card Service Operator-Services System
without the assistance customers to dial billing information Calling Card Service permits
is sent from the coin or non-coin calling of an operator The billing information Both the DTMF must be enabled telephone via DTMF signaling As result pads Service coin can be used with Calling Card coin-first and dial-tone-first telephones because the end office can continue to return any However dial-tone-first is preferred Card Service will the on coin arranged for Calling initial deposit and pad telephones Because of the additional remain enabled throughout call for end-to-end signaling the details coin retention and Calling Card Service complications to the interfaces due to Service calls are in this section of coin control for both ACTS and Calling Card given
6.18.4.1 Dial-Tone-First
dial-tone-first coin telephones Multiwink and EIS coin control enable DTMF pads in Card Service C-series stations require Inband coin control maybe used with Calling in the dial-tone-first mode Signaling modification for pad enablement when operating There however three similar with multiwink and EIS methods are protocols are
important differences
offices with positive Multi wink All calls are connected to operator-services toll If the the station to the totalizer in the mode battery applied to place from coin is to office determines that call telephone operator-services be sent an signal must receive Calling Card Service treatment operator-released determined that the call If it is subsequently immediately to enable the DTMF pad when the the office sends an operator-attached signal is to be sent-paid operator With EIS and no dialed prefix calls arrive at the paid key is depressed However with The same applies to multiwink operator office positive battery
6-188 SR-TSV-002275 SOC Notes on the LEC NetworksI 994
Issue April 1994 Signaling
and nonchargeable number calls arrive with negative battery applied
eliminating the need for the initial operator-released signal As with multiwink an
call is operator-attached signal is sent when the paid key is depressed if the
subsequently determined to be sent-paid
Interim Overtime Seizures EIS uses combined coin-collect/operator-released With used signal after the seizure multiwink separate signals are
Ringback Protocol This is described in Section 6.17.3
With both types of coin control the pad is enabled on coin telephones except during Card Service and intervals when coin deposits are being made Coin control with Calling dial-tone-first is discussed in the following sections
ACTS Call With Multiwink Signaling and Dial-Tone-First The end office
the applies positive battery to the coin station immediately before connecting to
is and the initial operator-services office The ACTS equipment connected deposit requested If problem is encountered an operator is also connected When the initial charge has been satisfied the ACTS equipment and operator if attached is released and the If the an operator-released signal transmitted to the end office to enable DTMF pad call does not complete for example reaches intercept reorder busy or no answer coin return is sent prior to releasing back When the call completes but terminates during the initial period coin collect is sent prior to releasing back If the initial period expires and the call is still in the talking state coin collect is sent approximately seconds before the end of the initial period This is followed by an announcement at the end of the period Should an interim overtime seizure be required an operator-attached signal is sent before the ACTS equipment is connected
call When coin-collect signal may be needed after partial deposit on large charge coin collect the deposit is complete an operator-released signal is sent followed by
On calls that terminate with charges due an operator-attached signal is sent followed by
After the coin ringback if the calling party has gone on-hook charges are satisfied collect is sent followed by release back An operator-released signal is not sent at the end of call The following listing shows the sequence of typical call with pertinent minimum timing information The sequence begins with completion of the AM digits
48 VtostationDThlFpaddisabled
AM start signal complete
2.2-second delay
ACTS announcement
Coin deposits
Operator-released sent enabled
Conversation interval
6-189 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Signaling
of initial Coin collect approximately seconds before end of initial period at end
period for OSPS
after initial for Announcement at end of initial period 1.8 seconds period OSPS
10 Conversation interval
11 Announcement
seizure disabled 12 Operator-attached signal sent for interim overtime DTMF pad 600 after announcement for Operator-attached signal sent ms OSPS
13 Coin deposits
14 Coin collect if large charge
15 Coin deposits
16 Operator-released signal sent pad enabled
17 0.6-second delay
18 Coin-collect signal sent
19 Conversation interval
20 Calling-party on-hook
21 Operator-attached signal sent DTMF pad disabled
22 1.6-second delay
23 Ringback
24 Calling-party answer
25 2.0-second delay
26 Announcement
27 Coin deposits
28 Coin collect sent
29 1.2-second delay 1.1-second for OSPS
30 Release-back
ACTS ACTS Test Call with Muitiwink Signaling and Dial-Tone-First The correct of station with ACTS test call is used by the craftsperson to verify operation the detected coin denomination is given after each equipment An announcement stating the end of the call The listing shows the deposit The coins are returned at following minimum information The sequence sequence of typical call with pertinent timing the ANI begins with completion of digits
48 to station DTMF pad disabled
6-190 Notes the LEC Networks 1994 SR-IS V-002275 BOC on SlgnIng Issue April 1994
ANI start signal complete
2.2-second delay
Announcement
Corn deposits and responses
Calling-party on-hook
Corn return sent
1.2-second delay 1.1-second for OSPS
Release-back
Dial-Tone-First This Calling Card Service with Multiwink Signaling and typeofcallcomestoOSPSinthesamestateaSalACTSCSIIthatiS48 Vtothe
station placing the totalizer or signaling priority in the toll mode and possibly disabling Local the DTMF pad OSPS determines from tnink group information or Originating Station Treatment that the call is Station Treatment LOST or Originating OST query
is then sent to enable the eligible for Calling Card Service An operator-released signal pad The Calling Card Service announcement follows The calling party may enter the
If valid number is received the call calling card number at this time progresses caller chooses to talk to an without any additional coin-control signaling If the operator the switchhook or an operator may be reached by dialing flashing doing nothing attached No for approximately seconds at which time an operator is automatically If the caller chooses to the call an signal is sent prior to the attachment place sent-paid
the is on the From this operator-attached signal is sent when paid key depressed position shows the point the call is treated as normal sent-paid coin call The following listing information The sequence for typical call with pertinent minimum timing timing taken the or information in the listing does not include the time by LOST OST query
The query time adds to the stated delay
48 Vto station DTMFpaddisabled
AM start signal complete
0.75-second delay 1.55 seconds for OSPS
Operator-released signal sent pad enabled
0.6-second delay
Calling Card Service announcement
Valid number entered
Operator attached no additional signaling
Customer requests sent-paid
6-191 BOC Notes on the LEC Networks 1994 SR-TSV-002275 issue 1994 Signaling April
10 Paid key pressed
11 Operator-attached signal sent pad disabled
12 Coin deposit
13 Operator-released signal sent pad enabled
14 Conversation interval
15 Normal sent-paid treatment
ANt Faliure/ONI Call with Multiwink Signaling and Dial-Tone-First Since this call comes to OSPS with the totalizerin the toll mode and the DTMFpad is not needed Card while the operator is attached no additional signaling is required by the Calling Service interface
ACTS Call with EIS and Dial-Tone-First The ACTS call with EIS is the
same as with multiwink except for few of the coin-control signals After the coin
deposit during an interim overtime seizure combined coin-collect/operator-released for each function The shows signal is sent instead of separate signal following listing information the sequence of typical call with pertinent minimumtiming
48 to station DTMF pad disabled
ANT start signal complete
2.2-second delay
ACTS announcement
Coin deposits
Operator-released sent pad enabled
Conversation interval
Coin collect approximately seconds before end of initial period at end of initial
period for OSPS
for Announcement at end of initial period 1.8 seconds after initial period OSPS
10 Conversation interval
11 Announcement
overtime seizure 12 Operator-attached signal sent for interim DTMF pad disabled
Operator-attached signal sent 600 ms after announcement for OSPS
13 Coin deposits
14 Coin collect if large charge
15 Coin deposits
6-192 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue Apr11 1994 SignalIng
16 Combined coin-collect/operator-released signal sent pad enabled
17 Conversation Interval
18 Calling-party on-hook
19 Operator-attached signal sent pad disabled
20 1.0-second delay
21 Ringback
22 Calling-party answer
23 2.0-second delay
24 Announcement
25 Coin deposits
26 Coin collect sent
27 0.3-second delay
28 Release-back
ACTS Test Call with EIS and Dial-Tone-First End offices using EIS connect
calls to OSPS with negative battery applied to the station for DTMF pad enablement
Service Since this the totalizer or in anticipation of Calling Card piaces signaling must be sent at the of priority in the local mode an operator-attached signal beginning
the test call to switch to the toll mode The rest of the call is the same as with multiwink
signaling The following list summarizes the sequence
48 to station DTMF pad enabled
ANT start signal complete
1.6-second delay
Operator-attached signal sent pad disabled
0.5-second delay 1-second for OSPS
Announcement
Coin deposits and responses
Calling-party on-book
Coin return sent
10 0.3-second delay
11 Release-back
6-193 BOC Notes on the LEC Networks 1994 Sfl-TSV-002275 Issue AprIl 1994 Signaling
Dial-Tone-First As stated in the CallIng Card Service Call with EIS and enabled Thus there is no section above this call comes to OSPS with the DTMF pad multiwink In fact need to send an initial operator-released signal as with signaling the call on basis unless the caller chooses to talk to an operator and to place sent-paid
time must still determine if the call isto no coin signaling is required at any OSPS LOST/OST receive Calling Card Service treatment via trunk group information or query call flow The following listing shows typical
-48 to station DTMF pad enabled
ANT start signal complete
0.6-second delay 1.2-seconds for OSPS
Calling Card Service announcement
Valid number entered
Operator attached no additional signaling
Customer requests sent-paid
Paid key pressed
Operator-attached signal sent DTMF pad disabled
10 Coin deposit
11 Operator-released signal sent DTMF pad enabled
12 Conversation interval
13 Nonnal sent-paid treatment
ANI Failure/ONI Call with EIS and Dial-Tone-First When the call has been number from coin station eligible identified via the operator-entered calling as coming if the it it dialed or Of- Thus for Calling Card Service is not known whether was signal is sent operator indicates sent-paid by pressing the paid key an operator-attached
is in the toll If the paid key is to ensure that the totalizer or signaling priority mode
the is sent after the calling number is pressed before the calling number is entered signal call then as entered Otherwise it is sent when the key is pressed The proceeds
normal sent-paid call
6.18.4.2 Coin-First
receives from the end As stated in Section 6.18.1 coin-first telephone negative battery coin to the initial rate must office For the DTMF pad to be operational deposit equal until the returned or collected the pad is disabled be present in the hopper If corns are feature called coin retention was deposit equal to the initial rate has been made again
6-194 BOC Notes on the L.EC Networks 1994 SR-TSV-002275 SIgnaling Issue April 1994
for Card Service without additional developed to provide pad enablement Calling coin retention does not return the coins on calls deposits An end office operating with return the coins as soon as routed to OSPS Instead OSPS assumes the responsibility to they are no longer needed
of the number on all but OSPS will return the coins immediately after receipt calling
if the caller does not enter valid calling calls The coins are also returned on calls the coins card number within the allotted time interval If valid number is entered are
is detected so the will be available for retained until calling-party disconnect pad enabled for end-to-end only on Calling sequence calls Thus the pad is signaling the initial when the Card Service calls and sent-paid calls during period deposit
exceeds the initial rate
used with coin-first combined All three types of coin control may be strictly operation
coin-first and dial-tone-first is covered in later in this section However when
trunk the multiwink or EIS is used on coin-first groups operator-attached operator- not sent released and combined coin-collect/operator-released signals are
Coin-First Coin-first is ACTS Call with Multiwink or EIS and operation of after ANT is completed functionally the same with both types signaling Immediately is disabled at OSPS sends coin return signal to return the initial deposit the DTMF pad dial-tone-first that no this time From this point on the call is similar to except is sent The following listing shows operator-attached or operator-released signal
typical call sequence
-48 tostion coins retained DTMF pad enabled
ANT start signal complete
0.75-second delay
Coin return sent pad disabled
seconds Delay 1.8 seconds multiwink 2.4 EIS
ACTS announcement
if than initial rate Coin deposits pad enabled greater
Conversation interval
of initial disabled Coin collect approximately seconds before end period pad
at end of initial period for OSPS
initial seconds after initial period for OSPS 10 Announcement at end of period 1.8
11 Conversation interval
12 Announcement at interim overtime seizure
13 Coin deposits
6-195 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaflng
14 Corn collect if large charge
15 Corn deposits
16 Coin-collect signal sent
17 Conversation interval
on-hook 18 Calling-party
19 Ringback
20 Calling-party answer
21 2.0-second delay
22 Announcement
23 Coin deposits
24 Coin collect sent
second 1.1 seconds with OSPS 0.3 25 Delay 1.2 seconds multiwink multiwink EIS
26 Release-back
Multiwink or EIS and Coin-First Except for the initial 0-i- ACTS Test Call with with multiwink signaling corn return this call is the same as dial-tone-first operation the coin return The following listing With EIS the operator-attached is replaced by
shows typical sequence
enabled -48 to station coins retained DTMF pad
ANT start signal complete
seconds for 0.6-second delay 1.2 OSPS
Coin return sent pad disabled
1.6 seconds Delay 2.8 seconds multiwink EIS
Announcement
Coin deposits and responses
on-hook Calling-party
Coin return sent
0.3 second 1.1 seconds multiwink with OSPS 10 Delay 1.2 seconds multiwink EIS
11 Release-back
6-196 SOC Noes on the LEC Networks SR-TSV-002275 1994 SIgnaling Issue AprIl 1994
Coin-First On Calling Card Service Call with Multiwink or EIS and has Calling Card Service call the initial deposit is retained until the calling party
if There is no coin completed the call and the following sequence calls applicable If the caller chooses to be connected to an operator the coins are signaling throughout shows returned before the operator is attached The following listing typical sequence
48 to station coins retained DTMF pad enabled
ANI start signal complete
0.6-second delay 1.2 seconds for OSPS
Calling Card Service announcement
Valid number entered
Coin return sent pad disabled
Calling-party on-hook
Operator attached
Coin return sent
10 If not sent-paid no additional signaling
11 Delay 1.2 seconds multiwink 0.3 second EIS
12 If sent-paid normal sent-paid treatment
13 Multiwink 1.1-second delay for OSPS
14 Release back
ANI Failure/ONI Call with Muitiwink or EIS and Coin-First This call comes to number OSPS with the coins retained When the operator has entered the back calling
and OSPS determines the call is from coin-first telephone on trunk group marked for
office The call then as coin retention coin return signal is sent to the end proceeds
normal operator-handled call
6.18.4.3 Combined Dial-Tone-First and Coin-First
The combined dial-tone-first/coin-first mode of operation is temporary arrangement to Since there hardware facilitate the conversion from coin-first to dial-tone-first are end offices Both the C- and 1-series restrictions on its use it is not applicable to some
the totalizer or in the toll mode for sets require positive battery to place signaling priority will not immediate readout of all deposits The A-series coin-first coin telephones
the combined mode cannot be used with A- function with positive battery Therefore in C-series sets as series sets Also the positive battery disables the DTMF pad operating be made to dial-tone-first either coin-first or dial-tone-first station modification can of the C-Series stations to enable the pad regardless battery polarity However
modification does not work on coin-first sets Coin-first telephones require negative
6-197 BOC Notse on the LEC Networks 1994 SR-TSVOO2275 Issue AprIl 1994 Signaling
dial-tone-first/coin-first mode cannot be battery for pad enablement Thus the combined
is either multiwink or EIS used unless battery polarity control provided by signaling
both When the combined mode is used the operator-services system applies treatments
for Card Service to the incoming think on every call identified as eligible Calling in the other Each coin Neither treatment adversely affects the stations operating mode The telephone responds to its required signals as described in these sections following and information listing shows the sequence of the coin control signals timing
since the of is not known when the call comes in the In the listing below type telephone For the the DTMF first line stating battery polarity or coin status is deleted same reason
pad state is also deleted
ACTS Call Multiwink Coin-First and Dial-Tone-First
AM start signal complete
0.75-second delay 1.55 seconds for OSPS
Coinreturn sent
1.8-second delay
ACTS announcement
Coin deposits
Operator-released signal sent
Conversation interval
Coin collect approximately seconds before end of initial period at end of initial
period for OSPS
10 Announcement at end of initial period 1.8 seconds after initial period for OSPS
11 Conversation interval
12 Announcement
interim overtime seizure 13 Operator-attached signal sent for operator-attached signal
sent 600 ma after announcement for OSPS
14 Coin deposits
15 Coin collect if large charge
16 Coin deposits
17 Operator-released signal sent
18 0.6-second delay
19 Coin-collect signal sent
6-198 SR-TSV-002275 BOC Nos on the LEC Networks 1994
Issu Aprft 1994 SIgnaling
20 Conversation interval
21 Calling-party on-hook
22 Operator-attached signal sent
23 1.6-second delay
24 Ringback
25 Calling party answers
26 2.0-second delay
27 Announcement
28 Coin deposits
29 Coin collect sent
30 1.2-second delay 1.1 seconds for OSPS
31 Release-back
ACTS Test Call Multiwink Coin-First and Dial-Tone-First
ANI start signal complete
0.6-second delay 1.2 seconds for OSPS
Coin return sent
2.8-second delay
Announcement
Coin deposits and responses
Calling-party on-hook
Coin return sent
1.2-second delay 1.1 seconds for OSPS
10 Release-back
and Dial-Tone-First Calling Card Service Call Multiwink Coin-First
ANT start signal complete
0.75-second delay second for OSPS
Operator-released signal sent
0.6-second delay
Calling Card Service announcement
6-199 SR-TSV-002275 BOC Notes on the LEC Networks 1994 1994 Signaling APTII
Valid number entered
Coin return sent
on-hook Calling party
Operator attached
10 Coin return sent
11 Customer requests sent-paid
12 1.2-second delay 1.1 seconds for OSPS
13 Paid key pressed
14 Release-back
15 Operator-attached signal sent
16 Coin deposit
17 Operator-released signal sent
18 Normal sent-paid treatment
ANI Failure/ONI Call Multiwink Coin-First and Dial-Tone-First
Operator attached
Calling number entered
Customer requests sent-paid
Coin return sent
Paid key pressed
If not sent-paid no additional signaling
Calling number entered
If sent-paid normal sent-paid treatment
Coin return sent
10 Normal sent-paid treatment
ACTS Call EIS Coin-First and Dial-Tone-First
AM start signal complete
0.75-second delay 1.55 seconds for OSPS
Coin return sent
2.4-second delay
6-200 Networks SR-TSV-002275 BOC Notes on the LEC 1994
Issue April 1994 SignalIng
ACTS announcement
Coin deposits
Operator-released signal sent
Conversation interval
for Coin collect approximately seconds before end of initial period at end OSPS
10 Announcement at end of initial period 1.8 seconds after initial period for OSPS
11 Conversation interval
12 Announcement
13 Operator-attached signal sent for interim overtime seizure operator-attached signal sent 600 ms after announcement for OSPS
14 Coin deposits
15 Coin collect if large charge
16 Coin deposits
17 Combined coin-collect/operator-released signal sent
18 Conversation interval
19 Calling-party on-hook
20 Operator-attached signal sent
21 1.0-second delay
22 Ringback
23 Calling party answers
24 2.0-second delay
25 Announcement
26 Coin deposits
27 Coin collect sent
28 0.3-second delay
29 Release-back
6-201 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Signaling
ACTS Test CaH ElS Coin-First and Dial-Tone-First
AM start signal complete
0.6-second delay 1.2 seconds for OSPS
Coin return sent
2.0-second delay
Operator-attached signal sent
0.5-second delay
Announcement
Coin deposits and responses
Calling party on-hook
10 Coin return sent
11 0.3-second delay
12 Release-back
Dial-Tone-First Calling Card Service Call EIS Coin-First and
ANT start signal complete
0.6-second delay 1.2 seconds for OSPS
Calling Card Service announcement
Valid number entered or Coin return sent
attached Calling-party on-hook Operator
Coin return sent Customer requests sent-paid
Paid 0.3-second delay key pressed
Release-back Operator-attached signal sent
Conversation interval Coin deposit
sent 10 Normal sent-paid treatment 10 Operator-released signal
6-202 the LEC Networks 1994 SR-TSV-002275 BOC Notes on SignalIng Issue AprIl 1994
ANt Failure/ONI Call EIS Coin-First and Dial-Tone-First
Operator attached
Calling number entered or Customer requests sent-paid
Coin return sent Paid key pressed
number entered Customer requests sent-paid Calling
Paid key pressed Operator-attached signal sent
Operator-attached signal sent .0-second delay
Coin sent Coin deposits return
Coin Operator-released signal sent deposits
sent Normal sent-paid treatment Operator-released signal
10 Normal sent-paid treatment
6.19 Operator-Services Miscellaneous Services
include the Miscellaneous services muted through operator-services offices following
calls Calls from non-coin lines for person-to-person collect and other types of
Calls requiring screening to prevent fraud
Calls from post-pay coin stations
Calls from Charge-a-Call telephones
International dialed calls where applicable
More information on the miscellaneous services is available in FR-NWT-000271 Coin OSSGR Operator Services Systems Generic Requirements TR-TSY-000528 and Charge-a-Ca1l and TR-NWT-000506 Signaling Sections 6.1 6.4.2 pisy
000528 and TR-NWT-000506 are modules of FR-NWT-000064 LATA Switching
Systems Generic Requirements LSSGR.1
6.19.1 Combined Coin and Non-coin Operator-Services Switch interface
in Non-coin telephones may be connected to operator-services switch offices over trunks combined is both coin and trunk groups dedicated to non-coin traffic However that used Since non-coin non-coin traffic trunk groups are also telephones require negative
the for and end-to-end the design battery supply to enable DTMF pads dialing signaling to non-coin lines This of combined groups should always provide negative battery in end offices For requirement can limit the use of combined trunk groups some example 1/lA ESS switching system not equipped with outgoing trunks that are the station designed for Calling Card Service has no control of battery polarity to
6-203 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaling
coin traffic connected to the operator-services switch office Trunks carrying always
the totalizer in the toll mode non-coin traffic provide positive battery to place Thus these trunks Installation or cannot be routed to the operator-services switch office over EIS retrofit of trunk circuits compatible with Calling Card Service and permits combined coin and non-coin 1/lA ESS switching system to control battery polarity so be groups can used
6.19.2 Selective Class of Call Screening Code Assignments In Operator- Services Offices
switch is Selective screening of ANI-identifled calls to an operator-services possible call Candidates for Information digit is used to identify requiring special screening from such locations as coinless telephones including special screening are calls public and other inmate calling post-pay coin telephones hospitals hotels/motels public
institutions such as college dormitories
should be in band or possibly two Telephones using selective screening grouped single the and lower limits of the bands of numbers for easy identification by checking upper bands
the The billing for screened calls can be restricted to following categories
conditions Locally Assigned Assigned to meet local
Single Allowed Class
Sent-Paid Only
Credit Card Only
Special Billing Number Only
Collect Only
Double Allowed Classes
Credit Card and Special Billing Number Only
Sent-Paid and Collect Only
Collect and Special Called Only
Multiple Allowed Classes
Sent-Paid Credit Card and Special Billing Number Only
Sent-Paid Collect and Special Called Only
Bill Collect and Called Credit Card Special Billing Number to Third Special
Screened Hotel/Motel
6-204 SR-TSV002215 BOC Notes on the LEC Networks 1994 SIgnaling Issue AprIl 1994
6.19.3 Charge-a-Call Public Telephone Service
non-coin line Charge-a-Call public telephone is served by single party loop-start with no extensions and no custom-calling feanires It can only be used for originating calls This prevents fraudulent collect calls Charge-a-Call was originally known as
Coinless Public Telephone CPT service
6.19.3.1 Charge-a-Call Service Dialing Restrictions
calls that be made from all The following is list of Not Sent-Paid NSP or free may coinless phones
and Nil local directory assistance repair emergency calls
or 10 digits
01 to 12 digits overseas NSP
0-
800 XXX XXXX 800 Service calls
NPA 555 1212 directory assistance in foreign NPA
The Charge-a-Call customer can make NSP person-to-person calls request notify or number time and charge quotation and make call charged to the called partys billing OSPS will not However as is the case with coin lines and hotel lines accept special from the customer on coinless billing number OXX/1XX sXXXXiRAO calling call
Where BOC tariffs so provide the customer may call
NXX XXXX local NSP
In addition where available locally the Charge-a-Call customer can dial
411 or 555 1212 directory assistance in the home NPA
of calls Charge-a-Call customer is not permitted to make the following types
NXX CXXX sent-paid local or toll
in but not in others The parentheses indicate that the prefix is required some areas
Revenue Accounting Office
6-205 BOC Notes on the LEC Networks 1994 SRTSV002275 Issue 1994 Signaling Apr11
NPA NXX XXXX toll sent-paid
011 to 12 digits overseas sent-paid
will not leave Because the Charge-a-Call telephone cannot receive calls the operator the word for callback If the central office can ring back non-coin lines operator may
on-hook to time and use that capability to ring an customer give charge quote The
Charge-a-Call telephone has ringer Otherwise the operator cannot contact an on- the would call the hook customer who expects time and charges Ordinarily operator non-coin customer back via delayed call trunk
6.19.3.2 Charge-a-Call Trunking Arrangements
be routed the Where the Charge-a-Call line is identified by ANI the call can over
following
Individual 0- or non-coin trunk group
Combined and non-coin trunk group
Combined non-coin trunk group
Supercombined coin and non-coin trunk group
of The Charge-a-Call call is screened by using information digit and lookup table
restricted lines in OSPS See Section 6.19.2 for details on selective screening
be routed Where the Charge-a-Call line is not identified by AN the call must over
dedicated trunk group for screened traffic
6.19.4 Post-pay Coin
is coin that can coin but is not post-pay coin telephone telephone accept deposits equipped to return coins This mode is rare in the BOCs
6.19.4.1 Trunking Alternatives
There are three alternatives for handling post-pay coin
will traffic Dedicated post-pay coin trunk groups that carry only post-pay
where the kind of Combined post-pay coin and non-coin groups with AN screening call will be determined by table lookup
coin call will be Combined post-pay coin and non-coin groups where post-pay
identified by service tone that follows the position-attached zip tone
6-206 the LEC Networks 1994 SR-TSV002275 BOC Notes on SgnaIIng Issue ApilI 1994
combined coin and non- ANT screening should be used wherever possible on post-pay in bands for coin groups Post-pay coin station numbers are grouped together easy of the bands identification by checking the upper and lower limits
to use service tone Where the end office has no ANI capability it is possible trunk The traffic is divided into at identification of post-pay calls on combined groups
least three trunk groups
Combined 0-0 non-coin and 0-0 post-pay coin group
non-coin group
post-pay coin group
two dedicated trunk Where the end office has no AN or service tone capability post-pay
groups must be used
00 post-pay
post-pay
6.19.4.2 Restrictions
office trunks for Planners consider the following restrictions when planning end post-pay use
trunk Post-pay and prepay cannot be combined on the same group
traffic identified ANT then the When combined group carries non-coin by post-pay also be identified traffic on that group must by AN
if coin is provided it cannot On trunks using service tone identification post-pay calls result be combined with non-coin traffic This is because non-coin ON be unable to use to in nonloop seizure and the operator would keys required
identify post-pay calls
calls cannot share trunk group with In addition non-coin or post-pay coin ON coin must be served dedicated traffic Therefore non-coin and post-pay by that identification is used The trunk must be compatible trunk group when service tone release and unrestricted re-ring re-ring is it must have hold reverse make-busy guard the into on-or off-hook supervision from station
6.19.4.3 Signaling
coin calls in combined trunk groups or Where ANT screening is used to identify post-pay coin calls the format where dedicated trunk groups are used for post-pay signaling for minks that use service tones to remains the same as for non-coin calls However off-hook to the end coin the system sends an identify post-pay calls operator-services has been connected to the trunk serving the post- office 400 to 500 ms after the operator about 200 This will the zip tone and service tone ms pay coin call This delay separate
6-207 SR-TSVOO2275 BOC Notes on the LEC Networks 1994 issue April 1994 Signaling
service tone The the two tones order tone followed by prevents operator confusion by is received identification when the off-hook end office starts to send the service tone is 700 Precise high tone or precise low tone The service tone is approximately ms long
used as described in Section 6.22.2
6.19.4.4 Providing Ringback
with the coin calls the end office should be equipped To provide ringback on post-pay following
on the and -48 on the ring for 50 to Polar marginal coin control 130 tip Vontheringfor50to 100 ma 100 msalternatingwith48 Vonthetipand130
for the duration of the ringback key operation
on-hook wink of 75 ma ma sent and 50 to Ability to respond to single 50 150 ms received
Formats 6.19.4.5 Trunking Plans and Pulsing
for coin Here are the trunking plans used by many BOCs post-pay
With AM The non-coin traffic on one combined trunk group Combine all post-pay coin and 6-33 this with AN is shown in Table pulsing format for arrangement
traffic on traffic trunk and all non-coin Combine all post-pay coin on one group with AN is shown in second trunk group The pulsing format for this arrangement Table 6-33
trunk and all non-coin traffic on one Combine all post-pay traffic trunk traffic and all non-coin traffic on one group Combine all post-pay 6-34 format for this is shown in Table group The pulsing arrangement
non-coin traffic or Use six individual trunk groups for coin is shown in format for this with AN post-pay coin The pulsing arrangement Table 6-34
Without ANT Service Tone Identification
non-coin traffic one trunk and all Combine all post-pay coin on group ANT The format for this arrangement without traffic on second trunk group pulsing coin and non-coin traffic would be handled on is shown in Table 6-35 The below two additional trunk groups as described
coin and 0- non-coin Use six individual trunk groups for 0- post-pay Service tone this is shown in Table 6-35 traffic The pulsing format for arrangement
is not required
8-208 SR-TSV002275 BOC Notes on the LEC Networks 1994 issue April 1994 Signaling
6.20 Signaling to Automatic Intercept System
The Automatic Intercept System AJS serves end offices and works with either the AM or ONI of the called number The MS is covered in both TR-NWT-000505 Call
Processing Section and TR-NWT-000506 Signaling Section 6.1 6.4.2
The signaling formats used for both ANT and ON are shown in Table 6-38 Numbers disconnected in trouble or not equipped are translated in the end office to route incoming calls reaching these numbers to outgoing intercept trunks The intercept trunks can be arranged to identify the type of intercept and to transmit the information to the
MS The MS does not generate unique disconnect signal The disconnect is under control of the calling party The end office trunk must be held busy minimum of
450 ms before reseizure to allow time for the MS to restore to the idle state The features required in the trunks and interoffice signals follow Note End office EM outgoing trunks are converted to loop at the Automatic Intercept Center MC
Table 6-38 Intercept-Class Signals Transmitted to Automatic Intercept Center
Trunk
End Office Concentrator AN ON ON
Loop Signaling MY EM
Class Signaling Tip Ring Signaling MY
Regular KP 7d ST Battery Ground One pulse KP ST
Trouble KP ld ST Ground Battery Two pulses KP ST
or KP ST
Blankor KP07dST Brief130V Threepulses KP7ST
unassigned or on tip and ring number KP ST followed by
battery on tip
ground on ring
Failureto KP2ST
identify line number
Note If an announcement is given to the customer before the call is completed to the AIC
KP ST is transmitted to the AIC
Note Information digits and KP signals are optionaL
6-209 SR-TSV.002275 BOC Not. on the LEC Networks 1994 Issue AprIl 1994 Signaling
6.20.1 interoffice Signaling with ANI
Battery-and-ground signaling with reverse-battery answer supervision AIC Reverse make-busy feature to make the end office outgoing trunk busy from the
Idle condition on-hook with battery on ring and ground on tip
6.20.2 Interoffice Signaling with ONI or Operator Assistance
One class single class of intercept.traffic on one.trunk
With or without supervision
Supervision could be high-low bridge or dc signaling
No reverse make-busy feature
Idle condition same as ANT trunk
traffic Three classes three classes of intercept on one trunk
Table DC signaling or thai-pulse signaling see 6-38
No reverse make-busy feature
Idle condition same as ANT trunk
6.21 Carrier Group Alarm
of carrier failures on CarrierGroup Alarm CGA is used to minimize the effects
switching systems and on service CGA system should
Release customers from the failed circuits
Stop charging
Busy out the failed circuits
Prevent false charging
Prevent the failed circuits from seizing the central office equipment
the on the trunk equipment These objectives are effected by CGA equipment operating Several vintages of CGA systems This process is referred to as CGA trunk conditioning CGA handle exist Some are for use with EM signaling only Other systems loop or are included in the DS1 trunk reverse-battery signaling as well as EM signaling
terminations of digital switches
be divided into three The operation of CGA system can parts
Detection of the carrier failure
6-210 SR-TSV-002275 SOC Notes on the LEC Networks 1994
Issu AprIl 1994 SIgnaling
Conditioning the failed trunk
Reaction of the switching equipment to the processing of the failure
The carrier failure-detection circuit is generally in the carrier terminal With some carrier failure SPC switching systems the software has the capability to detect systems the within the machine perform at least part of trunk-conditioning process switching
The CGA equipment can be collocated with or where calling-party control is used remote from the switching system Where there is more than one link of signaling be collocated with the and equipment in facility CGA equipment can switching system at one or more locations remote from the switching system These several CGAs would perform the CGA trunk processing for trunk into switching machine Each CGA equipment would perform the think processing where the associated carrier link failed
The next few sections discuss CGA actions features and limitations in the order they would occur when carrier system fails and then restores
6.21.1 Call Processing Between Carrier Failure and Trunk Conditioning
After carrier failure occurs for example loss of synchronization in digital carrier system but before CGA trunk conditioning begins it is desirable to maintain the same supervisory state on each trunk as existed before the failure If the carrier cannot be restored in reasonable time for example 2.5 seconds trunk processing should be initiated to remove the thinks from service The time should be long enough to
the carrier before think but short maximize the possibility of restoring processing begins enough so that the customers using the facility are not more annoyed by the effects caused by the delay in processing the failure than they are by the effects of the carrier failure
This method of maintaining the previous supervisory state after failure is designed into
D4 channel banks and other similar digroup terminations Its advantage lies in its maintain connections even be lost due to bursts of capability to though signaling may carrier This errors with digital carrier or due to the time required to perform protection massive seizures of circuits method not only saves calls on short failures it also prevents trunk that were idle at the time of failure and prevents false charging before processing begins
have natural to remain in the same Single-frequency signaling units tendency
failure all supervisory state after the failure as they were in before the However single-
channel banks fail or frequency units and Dl and D2 can off-hook on-hook alternating between off-and on-hook
6.21.2 Trunk Conditioning
The first controls There are two methods of accomplishing trunk conditioning
with the and the second uses supervisory signals associated signaling systems auxiliary
6-211 SR-TSV002275 BOC Notes on the LEC Networks 1994 issue April 1994 Signaling
circuit to the central control of an electronic signals forwarded directly to the trunk or
switching system
control of Where trunk conditioning is accomplished through the supervisory signals forced on-hook If the affected trunk is an the associated signaling systems are
in the the on-hook incoming circuit or 2-way trunk circuit used incoming mode will force the release of the associated switching system thereby disconnecting effect in established calls The on-hook toward an outgoing trunk has no systems
release from the with calling-party control because the calling party can always
control is the on-hook the connection Where joint hold or operator used permits release calling party to
is the As will be seen in the sections that follow if supervisory conditioning only the trunk trunk conditioning used subsequent off-hook would trap the customer on should be used for the duration of the carner failure As result joint-hold trunks
the trunk canier failure with auxiliary trunk conditioning signals to busy out during
About 10 seconds after the failure is detected by the CGA equipment an auxiliary
the carrier terminal is to the trunk circuits of all outgoing and 2- signal from applied This forces them off-hook way trunks with calling-party control auxiliary signal and thereby making them appear busy to the switching system The 1-way incoming
joint-hold circuits remain on-hook
in the failed The disadvantage of the supervisory busy-out for 2-way trunk circuits is that failure can condition permanent signal is presented to the switching system large absence of this kind of carrier-failure tie up the office for short period of time In the the trunks can occur the trunk conditioning however repeated seizures on throughout
period of the carrier failure
be at the or at remote location Supervisory conditioning can applied switching system for remote trunk is that for calling-party control The only requirement conditioning state of the the failure of provisions are made to control the supervisory signaling during be the sole method of trunk the carrier system Supervisory conditioning can trunks and trunks conditioning for calling-party control Incoming using joint-hold
control remain on-hook during the carrier failure
the trunk circuit is Where the trunk conditioning is accomplished using auxiliary signals leads This made busy by closing contact between two auxiliary signaling auxiliary the trunk and remains until the carrier is signal is applied at the time processing begins rather short resistance this restored Since these auxiliary leads usually have ranges
situations the CGA and are method is usually limited to where switching equipment and 4ESS are for collocated The auxiliary signals for 1/lA ESS switching systems for the 4ESS the carrier group rather than single circuit Except switching system the trunk circuit for future usage but does not disconnect auxiliary signal makes busy any the trunk the call presently using
the of an to busy out Joint-hold or operator-control circuits require use auxiliary signal because the must the trunk during the carrier failure The signal is required supervision to the trunk circuit remain on-hook during the failure to prevent locking customer restored to normal When the carrier failure ends all supervisory signals are
6-212 Networks SR-TSV-002275 BOC Notes on the LEC 1994 SignalIng Issu ApilI 1994
The following sections discuss the ways that CGA with supervisory conditioning techniques can be applied to various types of signaling
CGA on trunks equipped with EM lead signaling with supervisory conditioning as and the busy-out method is the most frequently used arrangement on intertandem terminal and the tandem connecting trunks It has the advantage that the carrier and switching system do not have to be collocated All EM lead incoming 2-way control will in this 1- trunk circuits having calling-party operate mode Many EM function in this mode Where way outgoing trunk circuits will also 1-way outgoing be used circuits with this make-busy mode are not available 2-way trunk circuits can
trunks seized The disadvantage of this mode of make-busy is that the 2-way are on until the carrier failure This can cause shortage of common equipment permanent condition signal arrangements clear the
trunks This make-busy method should not be used with joint-hold or operator-control
the CGA on loop reverse-battery signaling trunks with supervisory conditioning as trunks are busy-out mode is method of trunk conditioning Since only 1-way available there is no false seizure of switching equipment Use of this method
feature in the trunk circuit These trunk requires reverse make-busy outgoing think circuits are limited to CAMA and TOPS trunks at present Since the TOPS
and trunks are circuits are operator-control supervision only CAMA LAMA
available for this method
CGA on thinks to 4ESS or 1/lA ESS switching systems uses central control for part of
the processing The carrier system furnishes loop closure on two auxiliary signaling of the carrier failure The leads to these electronic switching systems for the duration the on carrier loop closure causes the start of trunk processing within switching system trunk The 1/lA ESS group of 24 minks The 4ESS system does all processing on-hook from the failed or trunks switching system requires supervision incoming 2-way the failure In addition to the CGA trunk the 4ESS to process properly processing that does switching system also has software CGA trunk-processing capability not from the carrier or leads require either trunk conditioning equipment auxiliary signaling
6.21.3 Carrier Restoral
trunks As soon as the carrier failure is over processing to restore the affected begins each carrier the net result where The exact procedure is individual to system However
trunk is to return trunks the carrier system has direct or indirect control over processing does not control the CGA to idle state in matter of seconds Where the carrier system
the 4ESS manual intervention be required process for example switching system may
to restore trunks to service
either the end office or Carrier failure involving operator-services system can occur on The failed trunks are by the the tandem side of the operator-services system processed
the failure is between the end office and the carrier and signaling systems when switch office When the carrier failure is between the operator-services operator-services
6-213 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 Signaling
switch office takes indirect switch office and the tandem office the operator-services failures maintenance action to place the trunks out of service after two call-attempt
6.22 Call Progress Tones Audible Tone Signals
of this inform and customers of the progress or disposition Signals in category operators must conform to the telephone calls The audible signals must be easy to interpret and have freedom from transmission system design requirements for signal levels voice circuit noise or other signaling interference effects with respect to currents
systems
of to and not causing All tone sources meet the general requirements being easy interpret and exact level are not documented for all interference However the frequency content
It is not that additional tones There is no specific requirement for any tone expected
it is that existing requirements will be established for existing tones further expected is retired or tone sources will remain in service until the associated switching system of call tones until obsolescence dictates replacement of the source The level progress of 61 to 71 dBrnC The tone level should be usually but not always lies in the range transmission at the customers side measured where it is applied to the voice path calling termination of 900 of the incoming line or trunk equipment with
6.22.1 Precise Tone Plan
used in the 1/lA ESS 2/2B ESS 4ESS 5ESS The precise tone plan has always been and NEAX-61E including OSPS DMS-10 DMS-100F including TOPS EWSD central office is based four tones which in switching systems The plan on pure held to .5-dB variation and 0.5-percent frequency applications are amplitude The total of harmonics and variation These tones are 3504.40480 and 620 Hz power
it is least 30 the level measured where other extraneous frequencies is at dB below signal The tones are individually or in pairs applied to the voice transmission path assigned The levels of the tones are not modulated to form standard audible tone signals precise
included in Section 6.22.2 For information on precise tones see TR-NWT-000506
Signaling Sections 6.1 6.4.2
Tones 6.22.2 Precise and Nonprecise Call Progress
6.22.2.1 Dial Tone
The 440 at level of 13 dBmO frequency Precise dial tone consists of 350 plus Hz per dial its sound old difference in frequency of 90 Hz gives this tone buzzing Nonprecise Hz when tone alternator or by tone consists of 600 Hz modulated by 120 supplied by this the frequency gives 133 Hz when supplied by an interrupter Jn case modulating Other combinations were also used this tone its low-pitched sound
6-214 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
6.22.2.2 High Low and Class-of-Service Tones
Precise high tone consists of 480 Hz at 17 dBmO Nonprecise old high tone is nominally 500 Hz when supplied from tone alternator or 400 Hz from an interrupter
Low tone gets its name from the prominent 140-Hz beat Precise low tone consists of
480 620 level plus Hz at of24 dBmO per frequency Interrupted low tone is heard by the customer when line busy reorder and no-circuit conditions exist Class-of-service
used switchboards indicate of tones are at to the class service of the calling customer when more than one class is served by the same trunk group Class of service may be indicated by high tone low tone or absence of tone
6.22.2.3 Line Busy Tone
Line busy is low tone interrupted at 60 1PM with approximately equal tone-on and tone-off times It indicates that the called-customer line has been reached but that it is busy
6.22.2.4 Reorder Paths Busy All Trunks Busy No-Circuit Tone
This is low tone interrupted at 120 1PM which indicates that the end office switching paths to the called office or equipment serving the called customer are busy or that no tandem trunk is available This signal may also indicate condition such as timed-out sender or unassigned code dialed
To limited extent the relative tone-on and tone-off durations were varied at one time to differentiate between end and tandem offices and between types of tandem offices The precise tone plan calls for equal tone-on and tone-off times of 0.25 seconds Taking into account all classes and types of offices at the present time both the tone-on and tone-off durations may range from 0.2 to 0.3 seconds provided that the sum of the two durations is 0.5 seconds The named circuit conditions are indicated by the easily recognizable
120-JPM rate but no significance is attached to the relative tone-on and tone-off durations
Tone should be provided at end offices for 60 to 1201PM and at tandem offices for 120
1PM These same tones are received by the calling customer on direct-dialed calls In general customers are not instructed on the significance of each tone They try completing their calls again regardless of the tone received However detailed instruction concerning tone signals is sometimes given to PBX attendants
6.22.2.5 Audible Ringing
level Precise audible ringing consists of 440 plus 480 Hz at of19 dBmO per and has frequency This signal indicates that the called line has been reached ringing started It is also used on calls to operators special service long distance information
6-215 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Signaling Apdi
audible etc during the awaiting-operator-answer interval Nonprecise old ringing 40 Other combinations were also used typically consisted of 420 Hz modulated by Hz
6.22.3 Recorder Warning Tone
When recording equipment is used beep of 1400-Hz tone is connected to the line every
that the conversation is 15 seconds for 0.5-second interval to inform the distant party being recorded The tone source is located within the recording equipment and cannot be controlled by the party applying the recorder to the line
6.22.4 Network Tones
networks Tones Table 6-39 documents all tones currently used in the BOC intraLATA
are included if they are now in use in the network even though obsolete that is they
if would not be provided in newly installed equipment Tones are not included they be heard customers need not ever be interpreted by person even though they might by
or operators from time to time for example multifrequency signals Each tone appears of twice first in table of specifications see Table 6-39 and again in glossary tone meanings see Table 6-40 The tones are numbered consecutively in Table 6-39 and
appear under the same numbers and titles in Table 6-40
See the FCC Rules Code of Federal warning tone is not always required with recording equipment Regulations 47 Part 64 Subpart para 64.501c
6-216 the LEC Networks SR-TSV-002275 9CC Notes on 1994 Signaling Issue April 1994
Table 6-39 Call Progress Tones
NameNoIc FrequenclesHzNote Temporal Pattern Note LeveisNote
LowTone 480 620 Various -24 dBmYftequency
600X l2Oor600X 133 61 to 71 dBrnC
600 140 or 600 160 61 to 71 dBrnC
Various -l7dBmO High Tone 480
400 or 500 6lto7ldBrnC
Dial Tone 350 440 Steady -13 dBmWfrequency
See Low Tone Steady
except 480620
off.. -19 Audible Ring Tone 440 480 seconds on seconds dBmCVfrequency
420 40 or 500 40 seconds on seconds off.. 61 toll dBrnClfiequency
second off.. Line Busy Tone Sec Low Tone 0.5 second on 03
Reorder local Sec Low Tone 0.3 second on 0.2 second off..
toll Sec Low Tone 0.2 second on 03 second off..
480620 0.25 second on 0.25 second off..
followed 112 Alerting Tone 440 seconds on by
second on every 10 seconds
seconds Recorder Wanting 1400 0.5-second burst every 15
Recorder Connected 440 0.5-second burst every seconds
03 second off.. -24 10 Reverting Tone Sec Low Tone 03 second on dBmVfrcquency
11 Deposit Coin Tone See Low Tone Steady
12 Receiver Off-Hook
0.1 second off.. VU see text analog 1400206024502600 0.1 second on
second off.. 3.0 to new systems 1400226024502600 0.1 second on 0.1 6.OdBm/frequency
13 Partial Dial Tone See High Tone Steady
14 No Such Number 200 to 400 Frequency modulated at Hz
interrupted every seconds for
0.5 second
Initial 1.5 seconds followedby -l3dBniO 15 Busy Verification 440
10 seconds Tone Centrex 0.3 second every 7.5 to
seconds in No 1/lA ESS
See Notes and Footnotes at end of table
6-217 SR-TSV-002275 BOG Notes on the LEG Networks 1994 Issue April 1994 Signaling
Table 6-39 Call Progress Tones Continued
NameNote FrequendcsHzNote Temporal PatternNote LevelsNote
of 0.3 second 10 -13 dBmQffrequency 16 Call Waiting Tone 440 Two bursts
percent separated by 10 seconds
second -13 dBmWfiequency 17 Confirmation Tone 350 440 Three bursts of0.1 on
0.1 secondoff
second time attendant -13 dBmO 18 Indication of Camp-On 440 every
releases from loop
second 0.1 -13 dBmtYfrequcncy 19 Recall Dial Tone 350 440 Three bursts 0.1 on
second off then steady on
-l3dBm 20 Data Set Answer-Back 2025 Steady
milliseconds -10 dBmWfrequency 21 Calling Card Service- 941 1477 60
-3 ThP Prompt Tone followed immediately by
440 350 940 milliseconds exponentially -7 dBmO total
decaying at time constant
of 200 milliseconds
22 Order Tones See High Tone One to four short spurts
23 Coin Denomination
1050-1100 bell one tap
slot 1O 1050-1100 bell two taps
800 one stations 25 gong tap
See one beep
TR-TSY-000528 slot 1O two beeps
five stations 25 beeps
24 Coin Collected Tone See Low Tone Steady
25 Coin Returned Tone See High Tone 0.5 to second once
26 Coin Return Test Tone See High Tone 03 to second once
27 Permanent Signal See High Tone Steady
28 Service Observing Tone 135 Steady
-22 dBmO 29 Proceed to Send Tone 480 Steady IDDD -l7dBmO 30 Centralized Intercept 1850 500 milliseconds
Bureau Order Tone
-25 dBrn 31 ONlOrderTone 700 1100 95 to 250 milliseconds
22 31 are tones Note Tones through 21 are customer tones tones through operator
added to and the times sign means modulated Note For multiple frequencies the plus sign means
that the stated is indefinitely Note Three dots .. in the pattern description means pattern repeated
of to the circuit Levels are measured when Note Except where noted levels axe given at the point application to the office the transmission measuring test set is terminated with resistance equal impedance PBXs Pattern is second on seconds off.. for some
At operating position
6-218 the LEC Networks SR-IS V.002275 BOC Not. on 1994 SIgnaling Issue ApilI 1994
Table 6-40 Glossary of Call Progress Tones
Name Description
used with various for the Low Tone This is generic tone interruption patterns under their own specific tones listed below and described elsewhere
titles
Line Busy Tone Deposit Coin Tone Reorder Trouble Tone
Reverting Tone Dial Test Signal
No Circuit Tone Class of Service
No Such Number
used with various for the High Tone This is generic tone interruption patterns under their own specific tones listed below and described elsewhere
titles
Partial Dial Tone Intercepting Loopback Tone Test Permanent Signal Station Ringer Coin Returned Test Tone Class of Service
Coin Returned Tone
that the Dial Tone This tone is sent to customer or operator to indicate
dial It is receiving end is ready to receive DTMF signals or pulses dial that the used in all types of dial offices Normally tone means entire wanted number may be dialed however there are some rare where cases where the calling party must await second dial tone or wait for an operator after dialing an initial group of digits must
second dial tone before the rest of the number can be dialed
This is indication that is by the calling party to Audible Ring Tone ringing interpreted mean that the called line has been reached and that ringing has
started It is also used on calls to operators special service long
distance intercepting etc during the awaiting-operator wswer
interval
break indicates that the Line Busy Tone Low tone interrupted at 601PM 50-percent
called customers line has been reached but that it is busy or on
permanent signal
of indicates that Reorder Low tone interrupted at 120 1PM in all types offices the office the called customer office equipment or trunks to serving condition such as timed-out are busy This signal may indicate
sender or unassigned code dialed It is interpreted by customer or
In offices the Precise Tone Plan operator as reorder signal using and 0.25 second off the temporal pattern is 0.25 second of low tone
In other offices the intervals are 0.3 second of low tone and
and 0.3 second off 0.2 second off end and 0.2 second low tone tandem
6-219 SR-TSV.002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaling
Table 6-40 Glossary of Call Progress Tones Continued
Name Description
that has connected to the line emergency Alerting Tone Indicates an operator verification interrupt on busy line during call
connected to the line is used this tone is Recorder Warning Tone When recording equipment
conversation is recorded to inform the distant party that the being and cannot The tone source is located within the recording equipment
the recorder to the line This tone be controlled by the party applying
and is recorded along is required by FCC Rules with exceptions
with the speech
the customer his/her call has completed to Recorder Connected This tone is used to inform to leave dictate etc Tone recording machine and to proceed message which warns It is to be distinguished from the recorder warning tone recorded the customer that the conversation is being
10 RevertingTone ThesametyeofsignalaslinebusytOfleisUsedforrevextlngtohlem informs the subscriber that all systems The reverting signal calling line and that to while the line the called party is on the same hang up
is being ning
to coin informs the calling party 11 Deposit Coin Tone This tone sent post-pay telephone and that the coin should be that the called party has answered
deposited
off-hook customers to the receiver 12 Receiver Off-Hook Tone This tone is used to cause replace call and non-PBX off-hook on-hook on permanent signal tosi
line when ringing key is operated by an operator
that he/she has not begun 13 Partial Dial Tone High tone is used to notify the calling party measured after receipt of dial tone dialing within preallotted time he/she has not dialed enough permanent signal condition or that
This is to and dial digits partial dial condition signal hang up aga
6-220 SR-TSV-002275 SOC Not. on the LEC Networks 1994
Issue AprIl 1994 Signaling
Table 6-40 Glossary of Call Progress Tones Continued
Name Description
check the called 14 No Such Number This signal tells the calling party to hang up number and dial again Calls to unassigned or discontinued numbers
may also be muted to intercepting operators or preferably to
machine announcement system that verbally supplies the required
in this condition message In some offices reorder tone is returned
15 Busy Verification Tone Busy verification allows the Centrex attendant or operator-services
to call and be connected to line The busy Centrex operaor- operator busy both of the connection to inform services verification tone is applied to parties
them of the intrusion by the attendant or operator No tone is applied
if the station called for busy verification is idle
servicethat allows line to answeran 16 Call WaitingTone Call Waiting isaspecial abusy of incoming call by flashing the switchhook Audible ring instead
is line busy is applied to the calling line and the Call Waiting tone
that the called bears the applied to the called line So only party
tone the connection is momentarily broken and the other party to the that connection experiences moment of silence Flashing and the switcbhook places the existing connection on hold connects
customer to the waiting call
17 Confirmation Tone This tone is used to acknowledge receipt by automatic equipment of
it is used for information necessaiy for special services currently
Speed Calling dialed number has been recorded or Call
service is Forwarding dialed number has been recorded and
activated or Call Forwarding service is deactivated
Centrex attendant to hold 18 Indication of Camp-On Attendant camp-on service allows incoming calls to busy lines Each time the attendant releases his/her
involved in the call the talking connection from the loop camped-on if the indication of camp-on tone is heard by the called customer customer has subscribed to the indication of camp-on option The
attendant reconnects customer may get this tone several times as the timed reminders from the and releases from the loop in response to console
6-221 BOC Notes on the LEC Networks 1994 SR-TSV.002275 1994 Signaling Issue April
Table 6-40 Glossary of Call Progress Tones Continued
Name Description
19 Recall Dial Tone This tone is used with Three-Way Calling Centrex station dial
transfer and Centrex conference station or attendant services The
user on an existing connection flashes the switcbhook receives recall
dial tone and dials the number of the third party to be added to the connection
20 Data Set Answer-Back This tone is heard by customers when manually initiating data call
Tone It normally occurs shoitly after the onset of audible ringing and means that the remote data set has answered The data set at the
data calling end should then be put into the mode
card 21 Calling Card Service This tone is used to inform the customer that his/her credit
Prompt Tone information must be keyed in The first 60 ms of this composite tone This will is 941 Hz and 1477 Hz which is the DTMF digit tone
release any DTMF to dial-pulse conveiter in the connection
22 Order Tones High tones sent over end office or tandem trunks indicate to the
originating operator that the order should be passed and to the
receiving operator that an order is about to be passed
23 Coin Denomination Tones These tones enable the operator to determine the amount deposited in
coin telephones
24 Coin Collected Tone Low tone over coin recording-completing trunk informs the
originnling toll operator that the coin-control circuit has collected the
charge
25 Coin Returned Tone High tone over coin recording-completing trunk informs the
originating toll operator that the coin control circuit has returned the
charge when the connection is not completed also called coin-refund tone
tone is used to tell that tester has call 26 Coin Return Fest Tone High an operator completed
to his/her position over coin trunk
6-222 SR-TSV-002215 BOC Notes on the LEC Networks 1994
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Table 6-40 Glossary of Call Progress Tones Continued
Name Description
27 Permanent Signal customers line not in use which exhibits steady off-hook
condition is routed to permanent signal trunk High tone
superimposed on battery is supplied through resistance lamp to the
ring of the think The tone informs an operator or tester making
verification test that the line is temporarily out of service An
intermittent ground may also be applied to the ring of line left in the hold condition Typical reasons for the line condition are no
dialing within the allowed waiting interval handset is off-hook
low insulation resistance or other line trouble
In some offices if three or more digits are dialed but not complete
telephone number or code the call is released and dial tone is
returned
28 Service Observing Tone This tone indicates that the trunk to which it is applied is
being service-observed
29 Proceed to Send Tone This tone informs the operator that an overseas sender has been IDDD seized and the address information KP-CC-NN.ST should be transmitted
30 Centralized Intercept This tone tells the centralized intercept bureau operator that call has
Bureau Order Tone reached the position
31 ON Order Tone This tone tells the ON operator that call has reached the
position
6-223 BOC Notes on the LEC Network 1994 SR-TSV..002275 Signaling Issue AprIl 1994
6.22.5 Receiver Off-Hook Tone
The Receiver Off-Hook ROH tone alerts the customer that receiver has been left off- hook and is used to call the customer back to the telephone Enhanced 911 pay telephones etc. Studies in the 1960s showed an ROH tone level of Volume Units
VU was preferred
When digital switching appeared the switches could not pass the required ROH tone level There was large advantage however in how these switches handled permanent signals The lines that remained off-hook after timing-out dial-tone register are not placed back in service to seize new register and time-out again rather they are held out of service until the line returns to on-hook new study showed that much lower tone levels were nearly as effective as the old levels So new standard of to dBm was adopted for new digital offices Because the alerting action of the tone increases with the power level it is desirable to provide ROH at the highest permissible level within these limits Studies indicate that the customer response rate increases 0.5 percent per dB as tone power is increased over this range Estimates are that this improved customer response results in an additional 1000 completed calls and one less customer trouble report per dB of increased power annually in 10000 line office
The ROH tone cadence in the following section is used by all end offices in the BOCs
Also the ROH tone level of VU is used by all analog switching systems installed before the change in the standard This includes 1/lA and 212B ESS switching systems
new arrangement is used in new space or time-division switching systems
In the DMS-l0 switching system the ROH tone as well as all other tones and digits is generated by Pulse-Code Modulation PCM samples stored in memory on the Tone of Digit Sender circuit pack PCM samples the composite signal generated by combining 1400 Hz 2060 Hz 2450 Hz and 2600 Hz at dBm each are stored in memory Under direction of the main Central Processing Unit CPU the PCM samples are read out as required and processed through the line card Digital-to-Analog CD/A circuitry to produce the ROH tone at dBm
ROH tone is not signal used in the tandem network and is never placed on trunks In some cases the tone is applied to foreign exchange lines using carrier facilities
However digital carrier is immune to overload from the relatively high power level of the ROH tone
In some cases ROH tone is applied either automatically or manually to lines that could be connected to an attendant headset Several switching systems 1/lA ESS 2/2B ESS
5ESS and EWSD have facilities to prevent automatic application of ROH tone
Tests of RON tone on actual telephone connections showed the Sound Pressure Levels
SPLs varied from 109 to 110 dBA and 108 to 109 dB SPL dB SPL is 0.0002 dynes per square centimeter
6-224 SR-TSV-002275 SOC Not. on th LEC N.tworks 1994
Isaus AprIl 1994 Signaling
6.22.5.1 ROH Tone for Present Analog Switching Systems
Most switching systems apply ROH tone to line twice for approximateiy 50 seconds each time However the 2J2B ESS system applies ROH tone once for period of
40 seconds Therefore the ROH tone is well within Occupational Safety and Health
Administration OSHA limits which permit 110 dBA for 30 minutes and 115 dBA for 15 minutes
Because of the circuit used to provide ROH tone it is not possible to give individual tone levels at specific reference point Therefore the following sections will describe the
ROH tone generator distribution arrangement and measurement equipment in some detail
There are four oscillators one for each frequency shown on the left side of Figure 6-62 140020602450 and 2600 Hz The oscillators use circuit nonlinearities to limit output amplitude There is no per-oscillator adjustment keyer applies and removes power from the oscillators The keyer applies power for 0.1 second then removes power for 0.1 second on repetitive basis to provide 5-pps tone from each oscillator
MAIN FRAME SWITCH
Figure 6-62 ROH Tone Circuit Analog System
6-225 BOC Notes on the L.EC Networks 1994 SR-TSV002275
Signaling issu April 1994
resistor isolates each oscillator from common tone bus where all four tones are
controls the present at approximately equal amplitude potentiometer voltage supplied to the amplifier This is the only adjustable element in the ROIl tone generator and distribution circuit
The keyed and mixed tones are fed to the amplifier The output of the amplifier is balanced signal which is fed to the resistive distribution network The output of the amplifier is the location specified as the measuring location for adjustment purposes standard volume indicator see 1FF STD 152-1992 IEEE Standard for Audio Program
is attached the of the which is Level Measurement35 at output amplifier adjusted to give a1l VUreadingatthispoint
The ROH tone then passes through two resistors and repeat coil The tone is estimated to be at level of VU at this point and at level of VU after passing through the switching machine to the customers side of the main distributing frame However there is no requirement for tone level at these locations
6.22.5.2 ROH Tone for New Switching Systems
ROH tone for new offices is combination of 1400 Hz 2060 Hz 2450 Hz and
2600 Hz tones added together The tone frequencies should be within 2.0 percent of their nominal values and the total power of harmonics and other extraneous frequencies including quantizing distortion should be at least 15 dB below the total ROIl signal level Each frequency component of the ROH tone should be at level within dB of the other components and within the range of 3.0 to 6.0 dBm per frequency
6.22.6 102 Test Trunk
In modern office either digital tone or quiet termination is provided for maintenance applications The type of tone provided is dependent on the contents of
Read-Only Memory ROM For maintenance applications it forms highly stable common office milliwatt supply for general testing and calibration From the Code 102 test trunk the tone or quiet termination is available to the test position and is available for automatic trunk and line testing Connection of the test circuit and application of tests are under software control
Access to the digital tone stored in the ROM is controlled by the Maintenance Trunk Module MTM controller via the Trunk Logic Circuits TLC-1 and TLC-2 Refer to
Figure 6-63 The 1LCs serve as communication buffers for control and data signals between the MTM and the tone generator The tone generator is connected to the following inputs and outputs
Data Reception RDAI Bus for receiving data
Transmit Data XDAT Bus for sending data
6-226 SR-TSV-002275 BOC Notes on the LEC Networks 1994
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time slot for the Enable and to activate the respective TLC at the appropriate
required test
The first enable signal to arrive at one of the TLCs activates the address counters to cycle
is incremented the ROM via OR gate Ui and the channel controller The ROM address once per frame time 125 ms via the channel controller The card frame time is synchronized with the first enable signal by the channel controller which controls reset
the is to of the ifip-flop The 8-bit parallel output of the ROM representing tone applied form The the output buffer which converts the parallel PCM data to serial PCM output of PCM data is controlled by the Enable XE output from either of the TLCs and by the status of Signal Distributor SD from either TLC if SDo the PCM is presented to the XDAT bus if SDo the flow of the data to XDAT is interrupted and the quiet termination condition exists
Signal Distributor XEnabie
Trunk Logic Circuit Pulse-Code Modulation Maintenance Trunk Module Receive Data
Read Only Mernoiy
Figure 6-63 Illustrative Digital 102 Test Trunk and Tone Generator
6-227 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Signaling Issue Apill 1994
6.23 Other Miscellaneous Signals
6.23.1 Ringing
6.23.1.1 Ring Forward Re-ring
the called This is signal used by an operator at the calling end to recall an operator at end on an established connection It is originated by means of ringing key On trunks with EM lead signaling the outgoing trunk equipment generates single on-hook pulse for each activation of the ringing key As applied to tandem di1ing circuits ring forward is momentary on-hook of 100 30 ms transmitted toward the called end 50 to 140 ins received which is converted at the destination office to recall signal
On metallic trunks arranged for loop signaling dc-simplex 130-V ring-forward signal maybe sentfor 10030 ins
6.23.1.2 Ringback
Ringback is signal used by an operator at the called end of an established connection to recall the originating operator The operation of the called operators ringing key sends
the end that is converted recall the an on-hook pulse back to calling to signal on originating operators console Ringback continues as long as the called operators ringing key is operated Ringback is also used by an operator to recall customer or to alert the calling customer
the Operator-controlled ringing ringback is required on all coin lines to ring telephone alert the when the calling customer hangs up after the call is completed to customer has when an overtime deposit is necessary It is also used to summon customer who but has also been used to requested time and charge quote has hung up Ringback
if the caller identify the calling line on emergency calls on other than 4- or 8-party lines inadvertently hangs up before identifying the location of the emergency
If 4- or 8-party line customer has made an emergency call and then hung up the calling number will not be available at the operator-services office For emergency calls to
is the 2/2B ESS switching system special emergency key required at operator-services office in addition to the regular ringback key
Interoffice coin or post-pay coin trunks with the ringback feature can be arranged for unrestricted nngback or restricted ringback With the former ringing is applied whether the station is on- or off-hook In some cases ROH tone is applied instead of ringing
if station is when the station is off-hook With the latter ringing is applied only the on- hook Unrestricted ringback is provided for all coin and single-party lines Restricted ringback is used to guard against annoying customer if the operator should attempt to ring back against party line and rings the wrong party
6-228 SR-TSV-002275 BOC Notes on the LEC Networks 1994
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With loop trunks to the end office 20-Hz ringing or reverse-battery can be used as the ringback signal Non-coin trunks can use single wink while coin trunks can use multifrequency tones or multiwink as described later as ringback signal See Section
6.17.3 for ringback protocol from OSPS
6.23.2 Tones and Announcements
Tones and announcements are used to inform customers and operators of various conditions encountered on dialed calls They are also required for service analysis of conditions that result in failure to complete dialed calls Analysis data are used to evaluate administrative engineering and maintenance efforts to improve service
Tones are used primarily to identify the condition of called lines and network blockage or failure conditions Generally low tone interrupted at 60 1PM indicates that the called customers line has been reached but is busy low tone interrupted at 1201PM indicates that the end or tandem switching or transmission paths to the office or equipment serving the called customer are busy
Announcements are used when the condition encountered requiis explanation for either customers or operators Announcements explain the type and severity of the condition and suggest the appropriate action to be taken
With the widespread use of direct distance dialing variety of tones or announcements for the same condition can be confusing to the customer the service evaluator or the automatic call-detection devices that make use of tone and announcement information
Nonuniformity makes it impossible to analyze performance results with any degree of accuracy The use of standard prerecorded announcements allows service evaluators to identify each type of announcement by certain key words in the announcement
Automated call-detection devices identify calls terminating in announcement systems by use of prerecorded Special Information Tones SiTs SiTs are covered in detail in CB
154 Spec jJi cations for Special Information Tones SIT for Encoding Recorded Announcements.36
6.23.2.1 Special Information Tones
SiTs permit mechanized call detectors and classifiers to classify calls that reach recorded announcements resulting from network conditions to Reorder RO Vacant Code VC No Circuit NC Intercept IC and Ineffective Other 10 Five encoded SiTs RO SiT VC NC SIT IC and 10 are intended for use by the BOCs to indicate network conditions encountered in the intraLATA networks Two separate encoded SiTs RO
SiT and NC SIT are intended to indicate network conditions encountered in the exchange access or InterLATA networks Figures 6-64 and 6-65 provide further clarity in the use of SiTs in the BOC intraLATA and the interchange carrier interLATA networks In addition one tone has been designated for future use
6-229 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Signaling Issue AprIl 1994
An SIT as defined by the International Telecommunication UnionTelecommunication
Standardization Sector ITU-T consists of sequence of three precise tone segments with frequencies of 950 50 Hz 1400 50 Hz and 1800 50 Hz sent in that order
Each segment is allowed duration of 330 70 ms with silent interval of up to 30 ms between segments The nominal tone level is -24 dBmO with liniits of 1.5 dB measured with continuous tone The difference in level between any two segments is required to be less than dB The above requirements apply at the point at which tones are applied to the network The first and second tone segments have short or long duration and the frequency state is assigned to the lower or higher part of the frequency band allowed by ITU-T The third tone segment may be of long or short duration but is limited to the lower frequency state For this initial application the third tone segment has been assigned both fixed long duration and fixed lower frequency These fixed assignments provide reference or calibration points for detection devices
Internal HO Sl Office Blockage RO Sir RO SiT
RO SIT
Tone RO SIT MO or RO Tone RO sir or ROSIT
Internal
Office Blockaqe RO SIT Access Tandem
Direction of Call End Office
RO SIF and HO Tone- BOC Responsibility RO SIT- IC Responsibility
lnterexchange Carrier Switch
Figure 6-64 Reorder Condition
mO decibels dB relative to mW measured at the dB TLP
6-230 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Signaling
NC SIT
NC SIT
NC SIT
NC SIT
NC srr
NC SIT
Direction of Call
NC srr and RO Tone BOC Responsibility NC SIT- IC Responsibility
Figure 6-65 No-Circuit Condition
The encoding scheme for the eight categories is in Table 6-41 The duration encoding is represented by short CS and long designations and the frequency encoding is represented by high and low designations
Table 6-41 Encoding Scheme for Special Information Tones
Category Duration Frequency
ROSIT SLL ihi
VCSIT LSL hil
NC SiT LLL hhl
ICS1T SSL ifi
RO SiT SLL hil
NCSIT LLL ifi
10-SiT LSL thi
Future SSL hhl
6-231 BOC Notes on the LEC NetworksI 994 SR-TSV-002275 Signaling issue April 1994
The frequencies assigned for use in the SiT encoding method are shown in Table 6-42
Table 6-42 Frequencies for Use in SITs
First Segment Second Segment Third Segment
913.8 Hz 1370.6 Hz 1776.7 Hz
985.2 Hz 1428.5 Hz 1776.7 Hz
Application of SIT tones starting with the 985.2-Hz frequency may cause false detection
is close the milliwatt by automatic trunk-testing equipment because this frequency to transmission test tone Since the access of trunk-testing equipment to SiTs for example
is No-Circuit Announcement is relatively rare occurrence the false-detection problem not expected to be significant iinpainnent to trunk testing
The duration of each segment assigned for use in SiT encoding is as follows
Short duration 274 ma
Long duration 380 ma
The defined frequency states lie within 1TU-T tolerances They are designed to be stable to within 1.5 percent of nominal values and the duration states are stable to within percent of nominal
The interval between the segments of SiTs is between and ma Interruption within segment is less than ma To minimize the number of customers who may abandon third without listening to the standard announcement the nominal time gap between the tone segment and the beginning of the announcement is set as close to zero as possible with an allowed maximum of 100 ms for prerecorded standard announcements
Frequency flutter is limited to 0.2 percent in cassette recordings of an announcement other and percent at the point of application to the network The total harmonics and of distortion products are at least 25 dB below the total tone power at the point application
Exceptions The ITIJ-T tolerances for the duration states are satisfied on all current announcement systems Frequency states as implemented through 13A or equivalent digital announcement systems also satisfy 1TU-T tolerances However due to the imprecision of electromechanical announcement systems the ITU-T frequency tolerances
full may be exceeded by these older-generation machines As older systems are replaced 1TIJ-T compliance will be attained
The nominal tone levels for SITs are set at 24 dBmO with tolerance of 1.5 dB This tone level was selected to reduce the tone level differential with respect to the recorded
set the absolute level announcement 22 VU These levels and stability requirements of each tone segment and fulfill the 1TIJ-T requirement that the tone level difference
6-232 SR-TSV-002215 BOC Note on the LEC Networks 1994
Issue AprIl 1994 SignalIng
between any two segments be less than dB This tolerance will be satisfied with the digital machines but for older-generation machines tone level difference of up to 4.5 dB may be realized Table 6-43 displays the expected components of error for SiT application to the network and indicates the expected tolerances for digital and electromechanical announcement systems
Table 6-43 Tolerances for Announcement Machines
Condition Duration Frequency
Cassette Generation 1.0% 1.0%
Portable Playback 0.5% 0.5%
Electromechanical Announcement Machine 3.0% 3.0%
Digital Announcement Machine 0.0%
Totals 4.5% 1.5%
Special Announcements Some situations or locations require special announcements These announcements are not prerecorded and are prepared locally using blank cassettes that contain the appropriate prerecorded SIT
6.23.2.2 Equipment Operation
Announcement trunks should be equipped for delayed cut-through so that an announcement will be heard from the start of the message There is an audible ring during the interval before the start of the announcement and the interval should be as short as possible Announcements are brief and carefully prepared Announcement facilities should be well maintained to ensure the quality of announcements
Announcement systems used for intercepted numbers are arranged for operator cut- through
6.23.2.3 SITs Tones and Announcements used in the Network
6-44 list of with the Table provides treatments along typical announcements applied for incompleted call attempts for the various conditions encountered See CB 154 Specfi cations for Special Information Tones SIT for Encoding Recorded
Announcements36 for additional information The reorder call disposition generally results from the following four network conditions
6-233 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Signaling issue AprIl 1994
An internal office blockage for example failure to match In intraLATA In switching systems the generic disposition is currently reorder tone 120 1PM
interLATA switching systems disposition of reorder announcement equipped
with RO SIT should be the normal response
Failure to provide wink on an interoffice call attempt Call attempts between two condition should be intraLATA switching systems encountering no-wink provided with either reorder tone or an announcement equipped with RO SIT
See Figure 6-64 Call attempts encountering no-wink condition from an
intraLATA switching system directly connected to an interLATA switching system
are routed to an announcement equipped with RO SIT
Insufficient digits
All announcement trunks are busy
NC call dispositions result from the following two conditions
Failure to fmd an available interoffice trunk In an intraLATA switching system
when an intraLATA call attempt is originated or through-switched and fails to
obtain an interoffice trunk the appropriate disposition is either an announcement
equipped with NC SIT or reorder tone In intraLATA switching systems when
call attempt is being originated on interLATA access trunks or through-switched via an access tandem to an Interexchange Carrier IC and no trunk is available the appropriate response should be an announcement equipped with NC SIT
Likewise in an interLATA switching system or to an intraLATA switching
system the disposition is an announcement equipped with NC SIT
Calls affected by the application of network-management controls if controls are activated by the exchange carrier and disposition of calls blocked by those controls
is an NC announcement that announcement is encoded with NC S1T if similar
controls are activated by an IC the disposition is an announcement equipped with NC SIT
primary use of the recorded announcement machines is to provide an intercepting
message to calls reaching vacant or disconnected customer numbers One such machine
provides single channel with an announcement interval that is usually fixed for
particular installation It may be set to one of six intervals ranging from 11 to 36 seconds Means are provided to connect trunk at the beginning of an announcement
interval and repeat from one to nine announcements two or three is the usual number
and then to connect to an intercept operator Two machines are usually provided one for service and one for automatic standby In multioffice cities the machines are provided in
central location and intercept trunks may be brought into the center or to subcenters to
which the announcements are transmitted
smaller machine is used in small offices where the larger intercept machines cannot be
economically justified In this use changed numbers vacant thousands and hundreds
levels as well as all vacant or disconnected numbers are routed to the machine
Normally only one machine is provided This machine operates on stop-start basis
6-234 SR-TSV.002215 BOC Notes on the LEC Networks 1994
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When started all subsequent calls requiring intercept in the announcement interval are cut in immediately to the machine at any stage of the announcement cycle Provision can be made for subsequent transfers to an operator
Direct-dialed calls will reach these machines when required The announcements give the customer the proper action to be taken Also it is desirable to inform the customer that the announcement is recorded Connections to announcement machines should not return off-hook answer supervision
Table 6-44 contains some of the tones and announcements used by the BOCs
6-235 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Signaling Issue April 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
IntraLATA Call Rlllng
General Categories
Signal-to-Start Dialing Dial Tone EO
Connected to Called Audible Ringing EO
Line or to Operator Tone Trunk
Receiver Off-Hook Announcement or EO ROH ROH Tone
Line Busy 60 1PM Tone EO
Trunk Group Overflow 120 1PM Tone EOF
Announcement 120 1PM Tone EO/T
Overflow
Direct Inward
Dialing Trunk Group 60 1PM Tone EOF Overflow
All Trunks Busy Announcement or EOF Were sony all NC SITt
120 1PM Tone circuits are busy
now Will you
please try your call agam later
See Notes at end of table
6-236 SR-TSV-002275 BOC Notes on the LEC Networks 1994
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Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
IntraLATA Call
Handling Contd
Switching Blockages
No Dial Tone Situations Announcement or EO Were sorry due to
Quiet heavy calling we
cannot complete
your call at this
time Will you
please bang up and
try your call later
If your call is
urgent please try
again now
Internal Office Failure Announcement or EOF Were sorry your RO SIT Wink Received 120 1PM Tone No call did not go EO/LT or through Will you
Partial Digits Received please try your call again
6-237 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Signaling Issue AprIl 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
IntraLATA Call
Handling Contd
Switching Blockages Contd
Sender or Transmitter Announcement or E0F Were sorry all NC SIT
Overload 120 1PM Tone circuits are busy
now Will you
please try your call
again later
Special Network Conditions
Disaster Announcement to EOF With flexibility NC SIT
be recorded locally due to situation
using prerecorded Were sorry SIT cassette storm flood
tornadoes etc damage in or near city has blocked
your call Emergency calls may be placed through your
operator
Network-Management Announcement EOF Were sorry all NC SIT
Control circuits are busy
now Will you
please try your call again later
6-238 SR-TSV.002275 BOC Not. on the LEC Networks 1994 lssu April 1994 SignalIng
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
IntraLATA Call
Handling Contd
Spedal Network Conditions Contd
Work Stoppage Announcement EO Were sorry
because of work
stoppage the
operator will be
delayed in helping
you lfyourcallis
urgent stay on the
line and the
operator will
answer as soon as
possible
Emergency Announcement EO/T Were sony due to NC SiT
Announcement telephone company
facility trouble
your call cannot be
completed at this
time Will you try your call again
Network Management 60 1PM Tone EOF
7- or 10-digit code Recording on
Controls Emergency Announcement
Arranged for Immediate Cut-
Through
6-239 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Signaling Issue AprIl 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
IntraLATA Call
Handling Contd
Special Network
Conditions Contd
Network-Management Announcement EOr Were sorry all NC SIT
7- or 10-Digit Code circuits are busy
Controls Switches now Will you
Equipped with CCS please try your call
inter
Vacant Number Announcement EO Were sorry your IC SiT
Intercept or Vacant call cannot be
Levels in Small Offices completed as dialed
with Only One or the number has Announcement Channel been disconnected
Please check the
number and dial
Prefix Code Access Announcement EO Were sorry it is 10 SIT
Code Dialed in Error not necessary to
dial or
when calling this
number Will you
please bang up and
ny your call again
Prefix Not Dialed Announcement EO Were sorry you 10 SIT
Prefix Not Dialed must first dial
Prefix Not Dialed or when
calling this number
Will you please
hang up and try
your call again
6-240 SR-TSV-002215 BOC Notes on the LEC Networks 1994
Issue April 1994 SIgnaling
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InfraLATA Call
Handling Contd
Contd
Vacant Code Announcement EOF Were sorry your VC SIT Unauthorized CAMA call cannot be
UCA or completed as
Plus Unauthorized dialed Please
Code check the number
and dial again
Nonworking 911 Announcement EO1T 911 is not VC SIT
working emergency
number for your area For
emergencies hang
up moment and
dial your operator
Numbers Intercepted
Vacant or Disconnected Announcement EO Were sorry you IC SIT Number Includes have reached Vacant Thousands and number that has
Hundreds or Numbers been disconnected
withDenied orisnolongerin
Terminating Service service If you feel
you have reached
this recording in
error please check
the number and try
your call again
6-241 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Signaling Issue AprIl 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
IntraLATA Call
Handling Contd
Numbers Intercepted Contd
Centrex Nonworking Announcement to EO Were sony the IC SIT
Stations First Choice be recorded locally number you have
using prerecorded reached is not in
SIT cassette service If you are
calling the ABC
Co please dial XOOQ
IC SIT Second Choice Announcement to EO Were sorry the
be recorded locally number you have
using prerecorded reached is not in
SIT cassette service Please dial
the main listed
number for the
company you are
calling
Intra-PBX Calls Served Announcement E0 Were sorry your 10 SIT
by Centrex Offices for can cannot be
Unassigned or completed as
Restricted Codes dialed Please
check the number
and try again or
call your attendant
to help you
6-242 SR-TSV-002275 BOC Nets on the LEC Networks 1994
Issue AprIl 1994 SignalIng
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InfraLATA Call Handline Contd
Numbers Intercepted Contd
High-Volume Customer Announcement to EO Telephone numbers IC SIT
Number Change be recorded locally at the ABC Co using prerecorded have been changed
SIT cassette For their new
numbers please dial NXX XQOQ
Receiver Off-Hook Announcement EO If youd like to
make call please
hang up and try again If you need
help hang up and
then dial your operator
Local Cain
Initial Coin Deposit Announcement to EO The call you have 10 SiT
be recorded locally made requires
using blank tape initial rate
deposit Please
hang up momentarily listen
for dial tone
deposit initial
rate and dial your
call again
6-243 BOC Note on the LEC Networks 1994 SR-TSV.002275 Signaling Issue April 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
IntraLATA Call
Bandling Contd
Lo Coth Contd
Deposit Required for Announcement to EO Alerting tone
Overtime be recorded locally Pause Excuse me
using blank tape please deposit
cents for the next
minutes if
cents is not
deposited within 25
seconds your call wilibe
automatically
terminate
Screened Line
Prefix Dialing Error Announcement EO Were sorry your 10 SIT
Screened Intercept call cannot be
completed as dialed
from the phone you
are using Please
read the insliuction
card and dial again
6-244 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
IntraLATA Call
Handling Cootd
Coinless Public
Telephone Service
Customer Dialing Sent- Announcement EO Were sorry your 10 SIT
Paid Call call cannot be
completed as dialed
from the phone you
are using Please
read the instruction
card and dial again
800 Service
Out-of-Band Announcement OSO Were sorry you VC SIT
have dialed
number that cannot
be reached from
your calling area
Out-of-Band Announcement OSO Were sorry your VC SIT Second Choice call cannot be completed as
dialed Please
check the number
and dial again
6-245 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Signaling Issue AprIl 1994
Table 6-44 Treatment Applied for lncompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Trealnent Note Announcement Note
IntraLATA Call
lIniIIing Contd
Remote Switching System RSSRSM
Local Service Only Announcement to RSS/RSM With flexibility as NC Sn
be recorded locally appropriate Were
using prerecorded sorry due to telephone
Sfl cassette company facility trouble only calls to numbers in the NXX
exchange and 911 can be completed at this
Voice Data Channel SIT or Announcement EO Were sorry due to NC Failure telephone company
facility trouble your
call cannot be
completed at this time
call Will you try your
again later
Custom Calling
Feature Custom-Calling Announcement EO Were sony your call 10 Sn cannot be completed as
dialed Please check
your instniction manual
or call the Business
Office for assistance
Custom-Calling Feature Announcement EO Were sorry your call 10 Sn cannot be completed as
dialed Please check
your instruction manual or call Repair Service
for assistance
6-246 SR-TSV-002275 BOC Not. on the LEC Networks 1994 Issus AprIl 1994 SignalIng
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InfraLATA Cali
Thindling Contd
Cuatom Cafling Contd
Speed-Calling List Full Announcement EO Were sorry addi
tional Speed-Calling numbers cannot be
entered at this time
Will you try again later
please
Custom-Calling List Announcement EO Were sorry we cannot RO SiT
Full process your custom-
calling request at this
time Will you try
again later please
Other
Temporarily Denied Announcement EO Were sorry the IC SIT
Service telephone you are
calling from is not in
service at this time
Flexible Incoming Call Announcement to EO Were sorry the IC SIT
Restriction be recorded using number you are calling
pre-recorded SiT cannot receive calls at
cassette this time Please call
again later
Customer-Controlled Announcement to EO Were sorry the IC SIT
Incoming Call be recorded using number you are calling
Restriction pre-recorded SIT cannot receive calls at
cassette this time Please call
again later
6-247 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Signaling Issue AprIl 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InterLATA Call
loXXx XXX Announcement EAEO Were sorry your call JO SIT
Not Valid cannot be completed
with the access code
you dialed Please
check the code and try
again or call your long- distance company for
assistance
1OXXX dialed Announcement EAEO Were sorry the long- NC SIT
Interexchange Carrier distance company you
Temporarily Out of have dialed is
Service experiencing
temporary service
problem Please try
your call again later
950-wxxx XXX Announcement EoPr Were sorry your call JO SIT
Not Valid cannot be completed
with the accesscode
you dialed Please check the code and dial
again or ask your long- distance company for
assistance
1OXXX Should be Announcement EAEO Were sorry the long- 10 SIT
950-WXXX distance company
access code you dialed
must be preceded by
the digits 950 Please
hang up and try your call agam
6-248 SH-TSV-002275 DOC Notes on the LEC Networks 1994
Issue April 1994 SIgnaling
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InterLATA Call
Handling Contd
950-WXXX Should be Announcement EAEO Were sorry it is not 10 SiT
1OXXX necessary to dial the
digits 950 before the
long-distance com
pany access code
Please hang up and try
your call again
1OXXX Omitted When Announcement EAEO Were sorry long- 10 SIT
Required First Choice distance company
access code is required
for the number you
have dialed Please
dial your call with the
access code
Second Choice Announcement EAEO Were sorry your call VC SIT cannot be completed as
dialed Please check
the number and dial
again
Toll Restriction or Announcement EAEO Were sorry your call 10 SiT Diversion cannot be completed as
InterLATA Restriction dialed from the phone
1OXXX from Restricted you are using Please Line read the instruction
1OXXX from WATS card and dial again Line
6-249 BOC Notes on the LEC NetWOrkS 1994 SR-TSV-002275 Signaling Issue AprIl 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InterLATA Call
RndIlng Contd
JO SIT 1OXXX1 NO AD1 for Announcement EAEO/AT Were sorry your call XXX cannot be completed
with the access code
you dialed Please check the code and dial
again or call your
long-distance company
for assistance
1OXXXPrefix Not Announcement EAEO Were sorry you must 10 SIT
Dialed diala1beforethe
area code when dialing
this number Will you
please hang up and try
your call again
1OXXXIntraLATA Announcement EAEO Were sony it is not JO SIT
XXX Restricted necessary to dial
long- distance company access code for the
number you have
dialed Please hang up
and try your call again
1OXXXInternalional Announcement EAEO Were sorry your call 10 SIT
XXX Domestic cannot be completed 1OXXXDomestic with the access code
XXX International you dialed Please
check the code and try
again or call your
long-distance company
for assistance
6-250 SR-TSV-002275 SOC Notes on the LEC Networks 1994 Issue Ap1I 1994 Signaling
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InterLATA Call
Handling Contd
1OXXXSAC or Nil Announcement EAEO Were sorry it is not 10 SIT
911 should notbe necessaiytodiala
blocked long- distance company
access code for the
number you have
dialed Please hang up
and try your call again
EAEO All Trunks Busy Announcement EAEO Were sony all circuits NC SIT to AT are busy now Will
you please try your call again later
EAEO Does Not Get Announcement or EAEO Were sorry your call RO SiT
Wink From AT 120 1PM Tone did not go through
EAEOIAT Intraoffice Will you please try
Failure your call again
EAEOIAT Does Not Announcement EABO/AT Were sorry due to RO SIT
Get Winks from network difficulties
Interexchange Carrier your long-distance call cannot be completed at
this time Please try
your call again later
6-251 BOC Notes on the LEC Networks 1994 SR-TSV..002215
Signaling Issue AprIl 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InterLATA Call
Handling Contd
EAEO/AT All Trunks Announcement EAEO/AT Were sorry all circuits NC SIT
Busy to Interexchange are busy now Will you
Carrier please try your call again
later
Interexchange Carrier Announcement IC/INC Were sorry the long- RO SIT
Intraoffice Failure distance company you
have selected is unable to
complete your call at this
time Please try your call
again
All Trunks Busy Within Announcement IC/INC Were sorry all circuits NC SIT
Interexchange Carrier are busy now Will you
later Network please try again
Interexchange Carrier
All Trunks Busy to EAEO/AT
Interexchange Carrier Announcement EOIAT Were sorry the long- NC SIT
Not in Service Or To Be distance company you
Recorded have selected is unable to
Locally complete your call at this time Please contact your
long-distance company
for assistance
6-252 SR-TSV-002275 SOC Noes on the LEC Networlca 1994 uue April 1994 SIgnaling
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InterLATA Call
Handling Contd
channels SiT All Channels Busy Announcement Cellular Were sony all NC
Within Cellular Carrier To Be Recorded Carrier are busy now Please try
Locally your call again later
Interexchange Carrier Announcement IC/INC Were sorry your call did RY SiT
Does Not let Wink not go through Will you
From EAEO/AT please try your call again
EAEOIAT Receives Announcement EAEO/AT Were sorry the long- RO SIT
Incorrect No of Digits distance company you
from IC/INC have selected is unable to
complete your call at this
time Please txy your call agam
SiT EAEO/AT Gets Digits Announcement EAEO/AT Were sorry your call VC for Nonsubtend Station cannot be completed as
dialed Please check the
number and dial again
Operator System Announcement EAEO/AT Were sony due to NC SIT
Overloads Plus heavy calling we cannot
complete your call at this
time Will you please
hang up and try your call
again later
6-253 BOC Notes on the LEC Networks 1994 SR-TSV-002275
SIgnaling Issue Apr11 1994
Table 6-44 Treatment Applied for Incompleted Call Attempts Continued
Applied Reportable
Encountered Returned at Condition
Condition Treatment Note Announcement Note
InterLATA Call
Handling Contd
Minus Announcement EAEO/AT Were sorry due to NC SIT
heavy calling the
operator will be
delayed in assisting
you If your call is
urgent stay on the line
and an operator will
answer as soon as
possible
LEGEND
Note Applied at
AT Access Tandem
EAEO Equal-Access End Office
EO End Office and/or Equal Access End Office
Sector Principal and/or Access Tandem
IC Interexchange Carrier Long-Distance Company
INC International Carrier Long-Distance Company
OSO Origiri2ting Screening Office 800 Service
RSS/RSM Remote Switching System/Remote Switching Module
Note Conditions repoitable by the Service Evaluation Bureau Reportable conditions that require
announcements also require SIT
SIT Information Section IC Intercept Special Tone See 6.23.2.1 for description of other SITs
The NC and RO SITs are applied by BOCs while the NC and RO SITs are applied by
Interexchange Carriers
5-254 SR-TSV-002275 BOC Not on the LEC Networks 1994
Issue April 1994 SIgnaling
6.24 Register Timing and Effect on Signaling
The software controlling registers in switches have timing functions to prevent their being held too long The intervals allowed for the registration of digits and for distant sender or register to be attached have an effect on signaling If any of the intervals allowed for digit registration are exceeded the distant office will route the call to reorder and release
The limits for digit pulsing that result from digit registration timing are given for the various switching systems in Table 6-24 Delays exceeding these intervals do not always result in reorder routing since these limits are necessarily based on minimum timing in the sender and registers Some of the intervals are automatically reduced during periods of heavy traffic to conserve equipment
The limits for the speed of attachment of register following receipt of connect signal from the calling office is typically 16 seconds in normal traffic 1A ESS system reducing to seconds in heavy traffic This measure minimiies the effect that delays in one office may have on other offices Without reduced intervals mutual delays between offices during periods of heavy traffic can pyramid seriously impairing service
6.25 Common Channel Signaling
Telephone signaling has been defined as basically matter of transferring information between machines and between humans and machines Signaling Systems for Control of Telephone Switching Bell System Technical Journal.3 current definition of signaling is the exchange of control information between elements of telecommunications network Such information includes supervisory signaling used to initiate and terminate connections and to indicate status general-purpose information transactions and network management The elements of todays networks include switches databases and operations centers
Common Channel Signaling CCS is signaling method in which the signals are no longer carried over the circuits/channels being controlled as is done with inband analog
for shared channel signaling example Instead separate common signaling link is used to convey the signaling information Thus CCS is really special-purpose data communications capable of using available data protocols and network technology
Signaling System SS7 is the latest protocol in use for signaling among switches and
It the in the databases was initially specified by CCITI 1980 Yellow Book recommendations with updates in the 1984 Red Book and in the 1988 Blue Book The equivalent standard for United States networks is given in the 1988 American National
Standards Institute full in ANSI standards Beilcore specffication is given TR
The CCITF is now called the International Telecommunication UnionTelecommunication Standardization Sector ITU-T
revised issue of the ANSI standards is expected to be published in 1993 The Beilcore specification is based on the Current view of the ANSI standard
6-255 BOC Notes on the LEC Networks 1994 SR-TSV002215
Signaling Issue AprIl 1994
NWT-000246 Bell Communications Research Spec fication of Signaling System Number 738 CC1TF Yellow Book Red Book and Blue Book and ANSI Amen can National 40 41 Standards for Telecommunications Signaling System No 739 42
SS7 protocol features help ensure reliable high-performance transfer of signaling
information in the face of network disturbances and failures Also application-level
procedures support call control for both Integrated Services Digital Network ISDN and
non-ISDN calls services associated with ISDN and non-ISDN calls generalized
transaction-oriented information transfer and management and operations signaling
In the words of the CC1TI specification The overall objective of Signaling System
No is to provide an internationally standardized general purpose CCS system
optimized for operation in digital telecommunications networks in conjunction with
stored-program controlled exchanges
that can meet present and future requirements of information transfer for inter-
processor transactions within telecommunications networks for call control remote
control network database access and management and maintenance signaling
that provides reliable means of information transfer in correct sequence without loss or duplication
The Beilcore specification currently consists of six parts
Message Transfer Part MTP three-level protocol providing connectionless message transfer
Signaling Connection Control Part SCCP providing sophisticated database
management and Open Systems Interconnection OSI network-service compatibility
ISDN User Part ISUP or ISDNUP providing ISDN call setup and control
harmonized to work with ISDN access protocolt
Transaction Capabilities Application Part TCAP designed for transaction-type and information transfer patterned after remote-operations protocol
Operations Maintenance and Administration Part OMAP provides SS7 messages and procedures for CCS management functions
specification of the interworking of SS7 and the ISDN access protocol Recommendation Q.93
The ISUP has been designed to also be used for POTS call setup and control
6-256 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 SIgnaling
References
FR-NWT-000064 LATA Switching Systems Generic Requirements LSSGR Beilcore 1994 Edition
TR-NWT-000506 Signaling Sections 6.1 6.4 Issue Bellcore September
1991 plus Revision November 1991 and Revision September 1992 module of LSSGR FR-NWT-000064
TR-TSY-000222 InterLATA Dial Pulsing Requirements Issue Beilcore
January 1986
TA-NPL-000912 Compatibility Information for Telephone Exchange Seriice
Issue Beilcore February 1989
ANSI T1.401-1988 Interface Between Carriers and Customer Installations
Analog Voicegrade Switched Access Lines Using Loop-Start and Ground-Start
Signaling American National Standards Institute 1988
ANSI Ti .4.05-1989 Interface Between Carriers and Customer Installations
Analog Voicegrade Switched Access Using Loop ReverseBattery Signaling
American National Standards Institute 1989
EIATIA 464-A-1989 Private Branch Exchange PBX Switching Equipmentfor Voiceband Application Issue Electronic Industries Association 1989
EIA 470-A-1987 Telephone Instruments with Loop Signaling Issue Electronic Industries Association 1987
IEEE STD 753-1983 Standard Functional Methods and Equipment for Measuring the Performance of Dial-Pulse DP Address Signaling Systems Institute of Electrical and Electronics Engineers Inc 1983
10 ANSI Ti .409-1991 Amen can National Standard for Telecommunications
Interface Between Carriers and Customer Installation Analog Voicegrade
Special Access Lines Using EM Signaling American National Standards
Institute 1991
ii IEEE STD 752-1986 IEEE Standard for Functional Requirements for Methods
and Equipmentfor Measuring the Performance of Tone Address Signaling Systems
Institute of Electrical and Electronics Engineers Inc 1986
12 TR-TSY-000510 System Interfaces Section 10 Issue Beilcore July 1987 module of LSSGR FR-NWT-000064
13 Channel Bank and PUB 43801 Digital Requirements Objectives ATT November 1982
14 TR-NWT-000303 Integrated Digital Loop Carrier System Generic Requirements
Objectives and Interface Issue Beilcore December 1992 plus Revision December 1993 and Supplement December 1993 module of TSGR FR NWT-000440
6-289 BOC Notes on the LEC Networks 1994 SR-TSV002275 Signaling issue AprIl 1994
15 TR-NWT-000507 Transmission Section Issue Bellcore December 1993 module of ISSGR FR-NWT-000064
16 TR-TSY-000763 Digit Simulation Test Tape Issue Beilcore July 1987
17 TR-TSY-000181 Dual-Tone Multfrequency Receiver Generic Requi rements for
End-to-End Signaling Over Tandem-Switched Voice links Issue Belicore March 1987
18 IEEE 455-1985 Measuring Longitudinal Balance of Telephone Equipment
Operating in the Voice Ban4 Test Procedures for Institute of Electrical and
Electronics Engineers Inc 1985
19 TR-TSY-000762 Impuise Noise Tape No 201 Issue Beilcore July 1987
20 FR-NWF-000271 OSSGR Operator Services Systems Generic Requirements Beilcore 1994 Edition
21 TR-NWT-000391 CIAS Feature Calling Identity Deliveiy Blocking
Features FSD 01-02-1053 Issue Beilcore September 1992 module of LSSGR FR-NWT-000064
22 TR-NWT-00003 CLASS Feature Calling Number Delivery FSD 01-02-1051 Issue Bellcore December 1992 module of LSSGR FR-NWT-000064
23 TR-NWT-000030 Voiceband Data Transmission Interface Generic Requirements
Issue Bellcore October 1992 plus Bulletin No September 1993 module of LSSGR FR-NWT-000064
24 SR-TSV-002476 CustomerPremises Equipment Compatibility Considerations for
the Voiceband Data Transmission Interface Issue Beilcore December 1992
plus Bulletin No September 1993
25 ANSI X3.4-1986 Coded Character Set 7-bit American National Code for
Infonnation Exchange Issue American National Standards Institute 1986
26 TR-NWT-000505 Call Processing Section Issue Beilcore May 1991 plus
Revision August 1992 module of ISSGR FR-NWT-000064
27 TR-TSY-000697 Feature Group FSD 20-24-0200 Issue Beilcore September 1989 module of LSSGR FR-NWT-000064
28 TR-TSY-000698 Feature Group FSD 20-24-0300 Issue Beilcore June
1989 plus Revision July 1990 module of LSSGR FR-NWT-000064
29 TR-NPL-000 175 Compatibility Information for Feature Group Switched Access
Service Issue Beilcore July 1985
30 TR-NWT-000504 Features Section Issue Beilcore April 1991 module of ISSGR FR-NWT-000064
31 TR-NWT-000690 IC/INC Interconnection FSD 20-24-0000 Issue Beilcore March 1991 module of LSSGR FR-NWT-000064
6-290 SR-TSV-002275 BOC Nets on the LEC Networks 1994
Issue AprIl 1994 SignalIng
32 TR-NPL-000258 Compatibility Info rmation for Feature Group Switched Access Service Issue Beilcore October 1985
33 TR-EOP-000085 through TR-EOP-000092 or TR-EOP-000315 Local Exchange Routing Guide LERG Beilcore March 1994
34 TR-TSY-000528 Coin and Charge-a-Call Issue Beilcore July 1987 plus revisions module of LSSGR FR-NWT-000064
35 tiF STD 152-1991 IEEE Standard for Audio Program Level Measurement
Institute of Electrical and Electronics Engineers Inc 1991
36 CB 154 Speczfl cations for Special Infonnation Tones SIT for Encoding Recorded Annowwements Issue ATT June 1983
37 Breen and Dahlbom Signaling Systems for Control of Telephone Switching Bell System Technical Journal Vol 39 November 1960 pp 1381-1444
38 TR-NWT-000246 Bell Communications Research Spec jfication of Signaling
System Number Issue Beilcore June 1991 plus revisions
39 CCJTF Yellow Book International Telecommunication Union Vol VI fascicle VI.6 1980
40 CC1TF Red Book International Telecommunication Union Vol VI fascicles VI.7 VI.8 1985
41 CC1TF Blue Book International Telecommunication Union Vol VI fascicles VI.7 VI.8 and VI.9 1988
42 ANSIT1.110 111 112113 and 114-1988Anerican National Standardsfor
Telecommunications Signaling System No.7 American National Standards Institute 1988
43 Reference Model of Open Systems Interconnection for CC1TF Applications X.200 CCIUBlue Boo/c International Telecommunication Union Vol Vifi fascicle Vffl.4 1988
44 Data Communication Networks OSI Protocol Specifications CC1TI Blue Book International Telecommunication Union Vol Vifi fascicle Vffl.5 1988
45 TR-NWT-000082 Signaling Transfer Point STP Generic Requirements Issue Beilcore December 1993
46 TR-NWT-000533 Service Switching Points FSD 31-01-0000 Issue Beilcore
January 1994 module of LSSGR FR-NWT-000064
6-291 BOC Notes on th LEC Networks 1994 SR-TSV-002275 Signaling issue April 1994
NOTE
All Beilcore documents are subject to change and their citation in this document reflects the most current information available at the time of this printing Readers are advised to check current status and availability of all documents
To obtain Beilcore documents contact
Beilcore Customer Relations
Corporate Place Room 3A-184
Piscataway NJ 08854-4156 1-800-521-CORE
908 699-5800 for foreign calls
BCC personnel should contact their company document coordinator and Beilcore personnel should call 908 699-5802 to obtain documents
To obtain ANSI documents call 212 642-4900
To obtain EIAJTIA documents call 2024574966
To obtain IEEE documents call 1-800-678-4333
To obtain ITU-T formerly CCITr documents call the 1TLJ switchboard at
41 227305111 and ask for document publication and sales
6-292 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 SignalIng
Bibliography
American National Standard for Telecommwzications Interface Between Carriers and Customer Installation Analog Voicegrade Special Access Lines Using EM Signaling
ANSI T1.409-1991 American National Standards Institute 1991
American National Standards for Telecommunications Signaling System No ANSI
T1.1 10 111 112 113 and 114-1988 American National Standards Institute 1988
Bell Communications Research Specfl cation of Signaling System Number TR-NWT
000246 Beilcore Piscataway NJ June 1991
Breen and Dahibom Signaling Systems for Control of Telephone Switching Bell System Technical Journal Vol 39 November 1960 pp 1381-1444
Call Processing Section TR-NWT-000505 Beilcore Piscataway NJ May 1991
CCITF Blue Book International Telecommunication Union Vol VI fascicles VL7 VL8 and VI.9 1988
CC1TF Red Book International Telecommunication Union Vol VI fascicles VL7 VI.8 1985
CC1TF Yellow Book International Telecommunication Union Vol VI fascicle VI.6 1980
Coin and Charge-a-Call TR-TSY-000528 Bellcore Piscataway NJ July 1987
CLASSSM Feature Calling Identity Delivery Blocking Features FSD 01-02 -1053 TR NWT-000391 Beilcore Piscataway NJ September 1992
CLASSMFeature Calling Number Delivery FSD 01-02-1051 TR-NWT-00003 Beilcore Piscataway NJ December 1992
Coded Character Set 7-bit American National Code for Infonnation Exchange ANSI
X3.4-1986 American National Standards Institute 1986
Compatibility Information for Feature Group Switched Access Service TR-NPL
000175 Beilcore Piscataway NJ July 1985
Compatibility Information for Feature Group Switched Access Service TR-NPL 000258 Beilcore Piscataway NJ October 1985
Compatibility Information for Telephone Exchange Service TA-NPL-000912 Beilcore
Piscataway NJ February 1989
Customer Premises Equipment Compatibility Considerations for the Voiceband Data
Transmission Interface SR-TSV-002476 Beilcore Piscataway NJ December 1992
Data Communication Networks OSI Protocol Specifications CCflT Blue Book International Telecommunication Union Vol Vifi fascicle Vffl.5 1988
Digit Simulation Test Tape TR-TSY-000763 Beilcore Piscataway NJ July 1987
6-293 BOC Note on the LEC Networks 1994 SR-TSV-002275
Signaling Issue April 1994
and 43801 November Digital Channel Bank Requirements Objectives PUB ATT 1982
Dual-Tone Mulhfrequency Receiver Generic Requirements for End-to-End Signaling Over Tandem-Switched Voice Links TR-TSY-000181 Beilcore Piscataway NJ March 1987
Feature Group FSD 20-24-0200 TR-TSY-000697 Beilcore Piscataway NJ
September 1989
Feature Group FSD 20-24-0300 TR-TSY-000698 Beilcore Piscataway NJ June 1989
Features Section TR-NWT-000504 Beilcore Piscataway NJ April 1991
IC/INC Interconnection FSD 20-24-0000 TR-TSY-000690 Beilcore Piscataway NJ March 1991
IEEE Standard for Audio Program Level Measurement IEEE STh 152-1991 Institute of Electrical and Electronics Engineers Inc 1991
IEEE Standard for Functional Requirements for Methods and Equipmentfor Measuring the Performance of Tone Address Signaling Systems IEEE STD 752-1986 Institute of Electrical and Electronics Engineers Inc 1986
Impulse Noise Tape No 201 TR-TSY-000762 Beilcore Piscataway NJ July 1987
Integrated Digital Loop Carrier System Generic Requirements Objectives and Interface TR-NWT-000303 Beilcore December 1992
Interface Between Carriers and Customer Installations Analog Voicegrade Switched
Access Lines Using Loop-Start and Ground-Start Signaling ANSI Ti .401-1988
American National Standards Institute 1988
Interface Between Carriers and Customer Installations Analog Voicegrade Switched
Access Using Loop Reverse-Battery Signaling ANSI Ti.405-1989 American National
Standards Institute 1989
InterLATA Dial Pulsing Requirements TR-TSY-000222 Beilcore Piscataway NJ
January 1986
L4TA Switching Systems Generic Requirements LSSGR FR-NWT-000064 Beilcore Piscataway NJ 1994 Edition
Local Exchange Routing Guide LERG TR-EOP-000085 through TR-EOP-000092 or TR-EOP-000315 all volumes issued quarterly Beilcore Piscataway NJ March 1994
Measuring Longitudinal Balance of Telephone Equipment Operating in the Voice Ban4
Test Procedures for IEEE 455-1985 Institute of Electrical and Electronics Engineers Inc 1985
6-294 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 SIgnaling
OSSGR Operator Services Systems Generic Requirements FR-NWT-00027 Beilcore Piscataway NJ 1994 Edition
Private Branch Exchange PBX Switching Equipmentfor Voiceband Application
EIAITIA 464-A-1989 Electronic Industries Association 1989
Reference Model of Open Systems Interconnection for CC1TF Applications X.200 CCJTF Blue Book International Telecommunication Union Vol Vifi fascicle Vffl.4 1988
Ritchie and Menard Common Channel Interoffice Signaling An Overview Bell System Technical Journa4 Vol 57 February 1978 pp 221-250
Schianger and Ong IEEE Journal on Selected Areas in Communications SAC-4 no May 1986 Pp 360-365
Service Switching Points FSD 31-01-0000 TR-NWT-000533 Beilcore Piscataway NJ
January 1994
Signaling Sections 6.1 6.4 TR-NWT-000506 Beilcore Piscataway NJ September 1991
Signaling Transfer Point STh Generic Requirements TR-NWT-000082 Beilcore Piscataway NJ December 1993
Specifi cations for Special Information Tones SIT for Encoding Recorded Announcements CB 154 ATT June 1983
Standard Functional Methods and Equipmentfor Measuring the Performance of Dial-
Pulse DP Address Signaling Systems l-FF STh 753-1983 Institute of Electrical and Electronics Engineers Inc 1983
System Interfaces Section 10 TR-TSY-000510 Beilcore Piscataway NJ July 1987
Telephone Instruments with Loop Signaling EIA 470-A-1987 Electronic Industries Association 1987
Transmission Section TR-NWT-000507 Beilcore Piscataway NJ December 1993
Voiceband Data Transmission Interface Generic Requirements TR-NWT-000030
Belicore Piscataway NJ October 1992
6-295 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Signaling Issue AprIl 1994
6-296
SR-TSV-002275 SOC Note8 on the L.EC Networks 1994
Issue AprIl 1994 Contents
Section Transmission Contents
Transniission ...fl 71
7.1 Introduction .... 7-1
7.2 Netvork Architecture 7-1
7.2.1 End-to-End Connections .... 7-1 7.2.1.1 Customer Premises Equipment 7-1
7.2.1.2 Subscriber Looos ...... 7-2
7.2.1.3 Switches 7-2
7.2.1.4 Trunks 72
7.2.1.5 Local Exchange Carriers 7-2
7.2.1.6 Interexchane Carriers... 7-2
7.2.1.7 End Office-to-End Office Connections 7-3
7.2.1.8 Connections to Other Networks ...... 7-3
7.3 Objectives and Lmu 7-3
7.4 Voice Transmission Impairments and their Control ...... 7-5
7.4.1 L4oss...... 7-5
7.4.2 NIessage Circuit Noise 7-6
7.4.3 Crosstalk ..m 7-8
7.4.4 Echo and Singing 7-8
7.4.5 Slope ... 7-16
7.4.6 Influence of CPE on Perceived Voice Quality 7-17
7.5 Voiceband Data Transmission Impairments and their Control 7-17
7.5.1 Impulse Noise ..... 7-17
7.5.2 Envelope Delay Distortion .... 7-18
7.5.3 Phase Jitter 7-18
7.5.4 Nonlinear Intermodulation Distortion 7-19
7.5.5 CNotched Noise ...... 7-19
7.5.6 7-20 Slips ......
7.5.7 Frequency Shift ..... 7-20 7.5.8 Slope 7-20
7.5.9 Customer Premises Equipment.... 7-20
7.6 tigita.1 .. 7-21
7.6.1 Synchronization 7-21
7.6.2 Characteristics of Digital Transmission 7-21
7.6.2.1 Error-Free Seconds.. 7-21
7.6.2.2 Bit Error Ratio 7-21
7.6.2.3 Severely Errored Seconds..... 7-22
7.6.2.4 Slips .. 7-22
7.6.2.5 Phase its 7-22
7.6.2.6 Timing Jitter 7-22
7.6.3 Bit Integrity 7-22 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Contents Issue AprIl 1994
7.6.4 ClearChannel Capability 723
7.7 Eigita.1 Data Transmission ...... m...... n...... n 723 Dedicated Services 723 7.7.1 1igital ...... _
7.7.2 Switched 56 ICIps Services ...... 724
7.7.2.1 Type PSDS Access ...... 7-25
7.7.2.2 Circuit-Switched Digital Capability 7-25
7.7.2.3 DT.PA.FlI1 .....n.....m...... n n.e 725
7.7.2.4 Interworking of PSDS Technologies 7-26
7.7.2.5 Switched 56 Kbps as an ISDN Bearer Service 7-26
7.7.2.6 Interworking Between PSDS and ISDN Switched 56
Kbps Data ...... 726
7.7.3 Switched 64 Service Kbps ...... _ 727 7.7.4 ISDN Switched DS1/Switched Fractional DS1 7-27
7.7.5 Switched Digital Services Performance ...... _ ...... 727
7.8 Fransniission Aspects of Ssvitches ...... _ 727
7.8.1 Comparison of Analog and Digital Switches 7-27 7-29 7.8.2 Digital Switch Distortion Performance
7.9 Adaptive Differential Pulse-Code Modulation Technology 7-30 7-31 7.10 Asynchronous Transfer Mode Technology ...... 4
7.10.1 A1I4 Cells ...... 731
7.10.2 ATM Cell Assembly and Disassembly 7-31
7.10.3 AIlvl Switching ...... 732
7.10.4 AFI1 Transport .. 733
7.10.5 AIIi1 Delay 734
7.10.5.1 Delay Associated with Cell Assembly and
Disassembly. .... 73.4
7.10.5.2 Delay Associated with SONET Rate
Conveion ...... 734
7.10.5.3 Delay Associated with Jitter Removal 7-34 7.10.5.4 Total ATM Delay 7-35
7.10.6 Transmission Errors and Cell Loss 7-35
7.11 End-to-End Performance. 7-35
7.1 1.1 Cirade of Service 735
7.1 1.2 Custonier opinion 736
7.11.2.1 Perception of Loss 7-36
7.1 1.2.2 L.oss/Isoise ... 736
7.1 1.2.3 Talker Echo.. 738
7.1 1.2.4 Loss/Noisefralker Echo 739
7.1 1.2.5 Listener Echo .4 739
7.1 1.3 Performance 739 7.12 Network Transmission Design _.._ 7-42 7.12.1 Network Transmission Plans 742 7-42 7.12.1.1 Via Net-Loss Plan .4 7.12.1.2 FixedLoss Plan 7-43
7.12.1.3 Metropolitan Area and Long-Distance Plans 7-43
II SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Contents
7-47 7.12.1.4 Loss Plan for Evolving Digital Networks....
7.12.2 L.oss Iinplenentation 748 7.12.2.1 Trunk lypes 748
7.12.2.2 Signal Level Conventions and Definitions Analog 750
7.12.2.3 Loss Implementation for Analog Trunks 7-52
7.12.2.4 Signal Level Conventions and Definitions
Digital ...... __ 753
7.12.2.5 Loss Implementation for Combination Trunks 7-54
7.12.2.6 Loss Implementation for Digital Trunks 7-54
7.13 operator Services Transmission 756
7.13.1 Transmission Objectives ...... m 756
7.13.2 Directoiy Assistance and Intercept Service 7-56
7.13.3 IntraLATA Long-Distance and Assistance Service 7-58
7.13.4 Operator Services Transmission Plan 7-58
7.14 Transnñssion Limits IntraJ.4A1TA Networks 760
7.14.1 Trunk Loss Limi 7-61
7.14.1.1 Test Tones 761 7-61 7.14.2 C-Message Noise Limi ..
7.14.3 Impulse Noise Requirenients 761
7.14.4 Balance Linñts...... 762
14.5 Loop Noise ...... n 764
7.14.6 Central Office Noise... 7-65
7.14.6.1 Cross-Office Noise 7-65
7.14.6.2 Impulse Noise ...... 766
7.15 Loop Transmission Jesign and Charactenzati 766
7.15.1 Revisecl Resistance Design .... 767
7.15.2 Modified Long-Route Design. 7-67 7.15.3 Concentrated Range Extender with Gain 7-68 7.15.4 Performance of RRD and MLRD Loops 7-69 7.15.5 The Carrier Serving Area Concept 7-69
7.15.6 Digital Subscriber Line 7-69
7.15.7 Spectruni Management in Loop Plant 772
7.15.8 Loop Surveys ...... 7-72 7.15.9 Basic Exchange Telecommunications Radio Service/Basic Exchange Radio Service 7-73
7.16 Interoperation with Other Networks ...... n 773 7.16.1 Switched Exchange Access 773 7.16.1.1 Access Connections 773
7.16.1.2 1ATS Access Lines.... 780
7.16.1.3 Transmission Performance Limi 7-80
7.16.1.4 InterLATA Directory Assistance 7-81 7.16.2 Interconnection with Private Networks 7-82
7.16.3 Interconnection with Cellular Mobile Radio Networks 7-83
References ...... 785
III BOC Notes on the LEC Networks 1994 SR-TSV002215 Contents Issue April 1994
Bibliography ...... n...... n...... n 787
iv SR-TSV402215 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Contents
List of Figures
Figure 71 IntraJ.4ATA Connections ...... 75
Figure 7-2 Comparison of Noise Weightings...... 7-7
Figure 7-3 Reflection Points and Echo Paths in Telephone
Connection ...... 79
Figure 7-4 Switching of 4-Wire Trunks at 2-Wire Switching Office 7-13
Figure 7-5 Terminal Balance Arrangements 7-14
7-16 Figure 7-6 Echo Canceler Application......
Fi77 Probable Nunibers of Coding Bits Used 729
Figure 7-8 Combining CBR and VBR Traffic Using Cell Switching 7-32
Figure 7-9 Customer Perception of End Office-to-End Office Loss Analog
...... 737
Figure 7-10 Customer Perception of End Office-to-End Office Loss Digital
Netvork ...... 738
Figure 7-11 Loss/Noise Grade of Service 7-38
Figure 7-12 Loss/Noise/Echo Grade of Service 7-40
Figure 713 GradeofService Distributions 741
Fie 714 IntraLATA Trunks ...... 746
Fie 715 Trunk Types ...... n 749
Points Figure 7-16 Analog Trunk Transmission Level ...... rn 7-51
Figure 7-17 Analog End Office to Analog Tandem... 7-52
Figure 7-18 Analog End Office to Digital Tandem 7-55
Fie 719 Digital End office to Iigital Tandem 755
Figure 7-20 Typical Automatic Intercept System Trunks 7-58
Figure 7-21 Operator Services System Plan 7-59
Figure 7-22 Basic Digital Transmission Plan Operator Services 7-59
Figure 7-23 Objective Loudness Ratings RRD ..... 7-70
Figure 7-24 Maximum Length of CSA Loops .. .. 7-71
Figure 725 ExchangeAccess Connections 775
Figure 7-26 Feature Group 7-76
Figure 7-27 Feature Group 7-77 BOC Notes on the LEC Networks 1994 SR.TSV-002275
Contents Issue April 1994
778 Figure 728 Feature roup C......
Figure 729 Feature 3roup ...... fl..flfl 779
Figure 730 ViAl. Service Configurations ...... 781
Figure 731 J.nterLATA Directory Assistance 7-82
vi SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue April 1994 Contents
List of Tables
table 71 IntraLATA Office Balance Luni 713
Table 7-2 Transmission Characteristics Analog versus Digital End
Offices ... 728
for Table 73 Bandwidths SON.ET Transport...... 733
Table 7-4 VNL and ICL Values for Trunks on Carrier Facilities 7-42
Table Intral4ATA Trunk I.1osses 75 I1. ... 746
Services Table 7-6 Loss Objectives Operator ...... 7-57
Table 77 CMessage Noise Lrni .. 762
Table 78 Impulse Noise Liini 763
Table 7-9 Loop Noise Objectives and Requirements 7-64
Table 710 End Office Noise Requirements 765
Table 711 Loop Design Plans 768
table 712 FOD lesign Loss dB...... 779
vii BOC Notes on the LEC Networks 1994 SR-TSV.002275
Contents Issue AprIl 1994
VIII SR-TSV.002275 BOC Notes on the LEC Networks 1994
Issue April 1994 TransmIssion
Transmission
7.1 Introduction
The subject of transmission covers broad range of performance considerations related to the physical facilities that compose the network architecture
Network architecture includes the numerous items that provide end-to-end connections
Perfonuance considerations include voice and voiceband-data impairments customer opinion and Grade of Service GOS transmission plans and methods for meeting loss limits objectives and test
These aspects of transmission as well as operator services loop transmission switched exchange access and interconnection to cellular mobile radio and private networks are discussed in this section
7.2 Network Architecture
7.2.1 End-to-End Connections
Customers making telephone calls use an integrated communications path in which entities providing portions of end-to-end intraLATA service are the exchange carriers Premises and the providers of Customer Equipment CPE at each end of the connection
For interLATA calls there is the additional presence of one or more Interexchange
Each of end-to-end connection is discussed below Carriers ICs part an
7.2.1.1 Customer Premises Equipment
wide variety of CPE manufactured and sold by many sources can be connected to the customers side of the demarcation point The efficiency of this equipment in converting an acoustic signal into an electric signal and the reverse is an important consideration in the development of any transmission plan The efficiency of the equipment affects the loudness noise and echo performance of the overall connection
All CPE must meet the requirements of Part 68 of the FCC Rules and Regulations
Section 13 In the discussion that follows CPE is assumed to be telephone set that also meets American National Standards Institute ANSI Standard EIA 470-A-1987 Telephone Instruments with Loop Signaling.1
with The FCC in its ruling associated Docket 88-57 has adopted the term demarcation point in place of network interface
7-1 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Transmission Issue AprIl 1994
7.2.1.2 Subscriber Loops
The effect of subscriber loops on end-to-end performance is also important Most of todays Local Exchange Carrier LEC loops conform to Revised Resistance Design RRD rules RRD rules apply to loops with up to 1500 resistance and 24 kft in length New loops up to 24 kft are implemented using the Digital Loop Carrier DLC as first choice DLC rules require that no loop should have more than dB of loss at 1kHz
7.2.1.3 Switches
The loop serving the customer connects to switch in the serving end office End office switches may be analog of electronic Step-by-Step or crossbar technology in sharply decreasing order of likelihood or digital units Interoffice calls involving complex routing pass through one or more intermediate offices called tandems Tandems may be analog but they are usually and ever increasingly digital
7.2.1.4 Trunks
Switches located in the same or different central office buildings are joined by trunks
These trunks generally use digital facilities although rapidly declining number of less carrier analog wire-pair facilities are used for distances of few miles or Analog facilities are deployed in some rural areas
7.2.1.5 Local Exchange Carriers
LECs provide service within Local Access and Transport Area LATA and furnish exchange-access service for the origination or termination of interLATA calls Exchange access requires an access connection from the end office to the IC Point of Termination POT This connection consists of either direct end office-to-POT segment or links connected via one or more tandems to concentrate traffic
7.2.1.6 lnterexchange Carriers
One or more ICs provide transmission path between LEC access networks An IC network connection can use single direct trunk or multiple tandem-switched links The
IC switch serving the LATA may be several hundred miles away The IC network may be configured with multiple paths between POTs to permit concentration and alternate
Some independent LECs and other entities particularly those associated with the Rural Electrification
Administration REA may use different design criteria
7-2 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue Apili 1994 Transmission
routing The IC may use dynamic method of routing where the path of call depends on available facilities and traffic volume
7.2.1.7 End Office-to-End Office Connections
Figure 7-1 shows the various connections that can occur in intraLATA networks These connections include the following
connection between Customers and both served by end office
connection joining Customer served by end office and Customer served by end office The end offices are linked via an Interend Office Trunk 101
connection joining Customer served by end office and Customer served by end office The two end offices are joined via Tandem Connecting Trunks
TCTs to sector tandems that are part of tandem-switching network The sector
tandems are connected via an Jntertandem Trunk LTI or via two lTrs if principal
tandem is used
7.2.1.8 Connections to Other Networks
Other networks may be involved in built-up connection There may be access trunking from an end office or tandem to cellular mobile carrier interface
Lines or trunks from an end office or tandem may provide connections to private network The owner of private network may function as an IC either for the owners use or for use by other firms Thus on any given call numerous possibilities exist for joining multiple networks
7.3 Objectives and Limits
Transmission criteria fall into the following two major categories
Objectives are goals that are classified by their intended use For example one
classification is the time frame in which the objective is to be met current near-term
or long-range Objectives may apply to trunks loops transmission facilities
switching systems or to overall connections They may be stated separately for the
design criteria the initial turn-up performance or the in-service performance of
piece of equipment or trunk There can be separate objectives for the performance
of elements such as trunks that are provisioned with newer versus embedded
technologies
Limits are established to provide practical means for meeting objectives Limits are
set on the performance of an individual circuit or small population of circuits
whereas objectives are typically established for large population Specific types of
test limits such as pre-service acceptance maintenance and immediate action are discussed in Sections 7.14 and 7.16.1
7-3 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Transmission Issue AprIl 1994
CPE Customer Premises Equipment
End Office EO
Plincipal Tandem
Sector Tandem
TCT Tandem Connecting Trunk
Figure 7-1 IntraLATA Connections
7-4 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 Transmission
Objectives for initial and in-service performance are typically expressed as distribution
although limits also may be specified to ensure that performance is within reasonable bounds
for network Most Performance objectives are goals performance objectives are current
However long-range objective is often stated as the performance distribution that achieve based trends in and telephone plant should on technology economics customer
expectations Requirements for new designs are usually based on satisfying such long-
term objectives
As telecommunications technology evolves transmission performance is reviewed and the objectives and limits are updated Voice transmission performance is analyzed transmission through field surveys laboratory tests and computer models that relate
impairments to customers opinions of transmission quality These models are based on
surveys of telephone plant performance to characterize the level of performance in the
network and on subjective tests that relate transmission impairments to customer opinion see Section 7.11
Transmission performance for analog data communication is assessed through computer
models based on laboratory and field analyses of error characteristics of modems The
computer simulations use modem models appropriate for each particular transmission
evaluation For digital data communication Bit Error Ratio BER models are used
7.4 Voice Transmission Impairments and their Control
Significant impairments to voice transmission performance are loss noise echo singing near-singing crosstalk and slope Other impairments which also affect voice transmission but have more critical impact on voiceband analog data transmission are discussed later
Where the same end office serves the calling and called customers transmission quality
depends primarily on loss and noise If the end office is digital near-singing also needs
to be considered On intraLATA routes of less than 200 mi singing crosstalk and slope
are additional potential impairments On routes of approximately 200 mi or more or
where delay is introduced by digital processing echo becomes consideration
7.4.1 Loss
Loss refers to the decrease in power level of signal traversing communication path
Acoustic-to-acoustic loss of an overall connection is the fundamental parameter for voice communication Measurements of acoustic-to-acoustic loss are obtained using acoustic sources and terminations that simulate human mouths and ears However because
telephone transmission plans consider both the overall connection and the elements that
make up the connection acoustic-to-electric electric-to-electric and electric-to-acoustic characteristics should also be considered
7.5 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Transmission Issue April 1994
Acoustic loss can be expressed in terms of either loss-frequency characteristic or
number that reflects averaging across the frequency band of interest The Jnstitute of
Electrical and Electronics Engineers IEEE STh 661-1979 Methods ofDetermining
Objective Loudness Ratings of Telephone Connections2 specifies the latter technique
which involves the concept of loudness loss as perceived by telephone listeners
Loudness loss for connection is affected by telephone set efficiency loop loss and
trunk loss Thus the design of telephone sets see Section 7.4.6 and loops see Section
7.15 at both ends of connection are as important to the quality of connection as the
design of trunks
The sending loudness efficiency of the telephone set/loop combination is described in terms of the Transmitting Objective Loudness Rating TOLR TOLR is measure in
decibels of the efficiency with which the telephone set/loop combination converts an
acoustic-pressure input at the telephone transmitter to an electric-voltage output
measured at the end office Pressure and voltage are stated in loudness terms per IEEE STD 661-1979
The receiving loudness efficiency of the telephone set/loop combination is described in terms of the Receiving Objective Loudness Rating ROLR ROLR is measure in
decibels of the efficiency with which the combination converts an electric voltage input
at the end office to an acoustic pressure output measured at the telephone set receiver
For telephone connections involving calling and called customers served by the same end
office the overall connection loudness loss is roughly the sum of TOLR and ROLR For telephone connections involving customers served by different end offices the connection loudness loss is close to the sum of TOLR ROLR and the 1-kHz end office- to-end office electrical loss see Section 7.12
7.4.2 Message Circuit Noise
Noise is any unwanted signal present in communication channel The unwanted signals in voiceband channel referred to as message circuit noise can originate from components of the transmission channel for example thermal noise from outside electrical interference power induction or from interference produced by one transmission channel being coupled to another crosstalk These unwanted signals can be annoying to the telephone user regardless of their nature or origin Thus noise should be controlled to satisfactory limits
The usual message circuit noise measurement is frequency-weighted average of the noise on voice circuit using voiceband noise measuring set as specified in IEEE STD 743-1984 Methods and Measuring the Transmission Characteristics of Equipment1or Analog Voice Frequency Circuits C-message weighting is normally used plot of this weighting is shown in Figure 7-2 along with the psophometric noise-meter weighting of the International Telecommunication UnionTelecommunication Standardization Sector 1TU-T formerly the International Telegraph and Telephone
Consultative Committee Measurements are expressed in dB above reference
7-6 SR-TSV.002275 BOC Notes on the LEC Networks 1994 issue Apfii 1994 Transmission
noise dBrnC The reference for the measuring set is 0-dBrnC reading which results from 1004-Hz tone at power of 90 dBm White noise of 0-dBm total power from to kHz is equivalent to 88 dBrnC Figure 7-2 also shows plot for the C-notched weighting C-notched noise is discussed in Section 7.5.5
Thermal and interference noise are primarily design-conirolled Techniques such as limits on applied channel load design limits on coders and decoders and the layout of outside plant provides this control Noise control in repeatered voice and carrier systems requires care in repeater and terminal placement inclusion of suppression devices to nullify disturbances and coordination with other telephone systems as well as power companies and radio services Voice-frequency systems and subscriber loops require good longitudinal balance to ensure low noise
-10
-20
-J
-30
-40
-50 100 200 300 500 700 1000 2000 3000 5000
Frequency in Hertz
Figure 7-2 Comparison of Noise Weightings
7-7 BOC Notes on the LEC Networks 1994 SR-TSV.002275
Transmission Issue April 1994
7.4.3 Crosstalk
Crosstalk is form of noise Inteffigible crosstalk is speech signal that is transferred
from one voice channel to another and is understandable under ambient circuit- and
room-noise conditions Thus intelligible crosstalk not only causes certain amount of
annoyance but also violates caller privacy The annoyance to the disturbed customer may
be heightened by doubts as to the privacy of his/her own conversation Intelligible
crosstalk can result from interchannel interference within transmission system or
between systems that are physically isolated There are three basic causes of crosstalk in todays networks
Energy coupling between adjacent Pulse-Amplitude Modulation PAM samples when shared codec coder/decoder is used in Pulse-Code Modulation PCM
system
Coupling between transmission media for example cable pairs
Use of common battery source with insufficient decoupling between circuits
Crosstalk may not be intelligible but may have the syllabic characteristic that indicates
the source is speech Because this type of crosstalk does not generally violate privacy
limits need not be as stringent as for intelligible crosstalk however the attention of
disturbed parties is more likely to be diverted than when an equal amount of ordinary
noise is present Therefore limits for unintelligible crosstalk are more stringent than for other forms of noise
PCM coders or decoders can be source of unintelligible crosstalk An ideal coder is
biased exactly half-way between the smallest positive and smallest negative decision
values This means that an input signal need exceed only one half of small step size to
change the transmitted code In real coders the bias can drift If PCM coder is biased
decision minute of the very close to level amounts noise or crosstalk in analog signal can reach or exceed the decision value causing an output signal that corresponds to full
step This is equivalent to one-bit coding of the interfering signal The resulting
crosstalk may not be intelligible but there is syllabic content
Babble is form of unintelligible crosstalk It is conglomeration of multiple
crosstalk signals that is speech-related however little or no conversation is understandable
7.4.4 Echo and Singing
Echo is the signal at any point in circuit that results from power being reflected from the primary speech path This reflection of signal can occur either at 4- to 2-wire junction in circuit or at an impedance irregularity in 2-wire circuit The reflected
signal can cause talker echo listener echo near singing and singing
Figure 7-3A shows generic end-to-end telephone connection The primary speech signal path is shown in Figure 7-3B The 2-wire path at each end includes the customer loop and may also include 2-wire switches and trunks The 4-wire path may
7-8 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 Transmission
Legend Amp1Hier
E1 Balancing Network
Primary Signal
Connoction Loudness Loss L1 L2
Talker Echo Path
TaikerEcho Path LossL1 L1 1.2 L2 RL2
I-I___l
Ustener Echo Path
UstenerEcho Path LossRL1 RL2 L2
Figure 7-3 Reflection Points and Echo Paths in Telephone Connection
7-9 BOC Notes on the LEC Networks 1994 SR-TSV-002275
Transmission Issue AprIl 1994
include 4-wire trunks and switches or may consist of single 4-wire digital end office
The 4-wire path is connected to the 2-wire path at each end by hybrid Since the impedance of the balancing network in the hybrid does not precisely match the
impedance of the 2-wire path some of the power arriving in the 4-wire path will be reflection reflected Multiple echoes can occur on connections that have multiple points but single echo usually predominates on such connections
The fraction of power reflected at 2-wire junction depends on the impedance mismatch
It is expressed in terms of return loss
Return Loss 20 log Z2/Z1 Z2
This formula for and It is correct for applies any two impedances Z1 Z2 approximately the echo reflected into the 4-wire where the of path at hybrid Z1 represents impedance the network and the of the 2-wire from balancing Z2 represents impedance path as seen the hybrid Return loss varies with frequency
The three types of echo-related interference that can occur in the transmission path are described below
Talicer Echo
Figure 7-3 includes diagram of the talker-echo path in the generic connection
Talker echo occurs when primary speech reflected at the far end returns to the
talker along the talker-echo path as shown in Figure 7-3C The talking customer
hears his/her own voice delayed by the round-trip delay of the echo path Talker
echo is annoying and can interfere with the talkers speech process The amount of
annoyance depends of the amplitude and delay of the echo see Section 7.11
Loss insertion and echo cancelers are used to attenuate talker-echo signals in the
transmission path Balance techniques are used to minimize the amount of signal
that is returned at reflection points
Echo Return Loss ERL is quantitative measure of echo path ioss over the
middle portion of the voiceband where signal energy perceived as echo is most
likely to be found ERL is defined in IEEE STD 743-1984 as the weighted average of the return losses measured with Return Loss Measuring Set RLMS using
bandpass-filtered noise with 3-dB points at 560 Hz and 1965 Hz
LIstener Echo
If the talkers speech reflected from the far end is again reflected at near-end
the impedance mismatch listener hears it twice The listener-echo path shown by the broken line in Figure 7-3D includes the ERL at both ends of the 4-wire path
and the round-trip electrical loss between the reflection points It can be seen that
any provision to control talker echo will also reduce listener echo Thus listener
echo is usually not concern on long connections where talker echo has been considered
7-10 SR-TSV-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 TransmissIon
Listener echo also referred to as near-singing distortion causes the listener to
perceive hollowness as if the talker were speaking into an empty barrel Listener
echo performance is judged on the basis of measure called Weighted Echo Path
Loss WEPL WEPL is the reciprocal expressed in dB of the average magnitude of the voltage gain of the closed listener echo path over the band from 200 to 3400 Hz
Digital end offices and host-remote links are potential sources of listener echo on
connections between two local subscribers due to the low loss of the equivalent 4-
wire path and the potential for poor balance at each loop hybrid For this reason
WEPL objectives have been formulated for the design of this type of equipment
the stated in of Since WEPL is closed-path parameter requirements are terms
distribution of connections rather than distribution of lines
WEPL is calculated quantity and the requirements apply to every possible
connection that an end office can provide Hybrid balance objectives have been
derived that if met will ensure that WEPL objectives are met provided that the
delay and loss of listener echo paths are controlled To meet balance objectives in
digital end offices the population of metallic loops is divided into two
subpopulations loaded and nonloaded with provision for separate hybrid balance
networks Return loss specifications apply to loop hybrids when they are
terminated in impedances that represent the two types of loops Loop-hybrid
balance is discussed later in this section
WEPL as well as requirements for both WEPL and hybrid balance is discussed in TR-NWT-000507 Transmission Section 74
SInging
Singing is caused by power circulating in transmission path It occurs in the
same manner as listener-echo and results in sustained loud tone on the
connection Singing occurs if the gains in line repeaters carrier channels or digital
end offices are high enough and the return losses low enough so that the round-trip
path gain at some frequency has magnitude greater than unity with phase shift
equal to or some multiple of 360 degrees
Singing normally occurs at frequencies near the upper or lower edge of the
voiceband where impedances are not well matched To measure the return loss at
the band edges measuring sets transmit shaped spectrum of noise in two narrow
bands The 3-dB points of the Singing Return Loss SRL low spectrum are
260 Hz and 500 Hz For SRL high the 3-dB points are 2200 Hz and 3400 Hz
The singing margin of connection is equal to the amount of gain that added to
the listener-echo path would just initiate singing As discussed previously the
hollow condition that occurs just before actual singing is called near-singing
7-11 BOC Notes on the LEC Networks 1994 SR-TSV-002275 TransmIssIon Issue April 1994
Control of echo and singing may involve the following methodologies in addition to insertion of loss in the transmission path
Through balance
Terminal balance
Hybrid balance
Balance in Remote Switching Units RSUs
Echo-control devices
Through Balance
The use of 4-wire facilities for intertandem trunks in the intraLATA network helps to minimize intermediate echoes Through balance is used to control echo at 4- to 2-wire conversions in analog 2-wire switching systems that connect intertandem trunks where mtraLATA end-to-end connections may exceed approximately 200 mi Few LATAs exceed the 200-mi figure 2-wire tandems are no longer common The amount of echo reflected at these 4- to 2-wire conversions depends largely on the impedance connected to limit the the 2-wire side of the hybrid see Figure 7-4 Office cabling-length restrictions range of these impedances to some degree and optimum balance is achieved for each hybrid using through-balance procedures Each trunk that is to be balanced is connected through the switching system to test termination The half path from the center of the switch to the test termination has been built-out so that its impedance is equal to the Build-Out median of the impedances of all half paths in the office The Network
Resistor and Capacitor NBOR and NBOC of the trunk hybrid are then adjusted to obtain the required balance Because of the office cabling restrictions an acceptable level of through balance can be assured on all switched connections Through balance requirements Pre-Service Limits PSLs and Immediate-Action Limits IALs are given in Table 7-1
Terminal Balance
Terminal balance procedures control the echo at 2-wire long-distance tandem office where an intertandem trunk is connected to Tandem Connecting Trunk TCT
Terminal balance measurements are performed at the tandem office with the TCT the connected to quiet tennination at the end office Figure 7-5 shows possible combinations of 2- and 4-wire facilities involved in terminal balance measurements If the end office and the tandem office are both equivalent 4-wire facilities no balance measurement is necessary or possible from the tandem office unless there is 2-wire facility between them Terminal balance requirements are given in Table 7-1
7-12 SR-TSV-002275 BOC Notes on the L.EC Networks 1994
Issue April 1994 Transmission
Echo Paths
Path
Intertandem Trunk lntertandem Trunk
Legend
Capacitor
NBOC Network Build-Out Capacitor NBOR Network Build-Out Resistor
Resistor
Amplifier or Coder/Decoder
Hybrid
Figure 7-4 Switching of 4-Wire Trunks at 2-Wire Switching Office
Table 7-1 IntraLATA Office Balance Limits
ERL dB SRL dB Measurement PSL IAL PSL IAL
Terminal Balance Analog switch
2-wire facilities
interbuilding 18 13 10
intrabuilding 22 16 14 10
4-wire facilities 22 16 15 11
Digital switch
2-wire facilities
interbuilding 18 16 13 11
intrabuilding 22 16 15 11
4-wire facilities 22 16 15 11 Through Balance 27 21 20 14
PSL Pre-Service Limit
IAL Immediate-Action Limit
7-13 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Transmission Issue April 1994
Tandem Balance Termination Office
2-Wire 2-Wire 2-Wire Switch End Office Connecting Switch Trunk
Termination
4-Wire Connecting Trunk --1
4-Wire 4-Wire Switch End Office Switch
NET Hybrid Balance Network Hybrid
IMP COMP Impedance Compensator PREC NET Precision Hybrid Balance Network
FIgure 7-5 Terminal Balance Arrangements
Hybrid Balance
Because digital end offices provide 4-wire-equivalent transmission path subscriber line
circuits must
Convert PCM-coded signals to analog signals and vice-versa
Provide 4-wire to 2-wire conversion
Minimize signal coupling from the 4-wire receive path to the 4-wire transmit path
Conversion from4-wire to 2-wire is accomplished with hybrid circuit However
control of echo and singing requires balance procedures that are more flexible than those used at TCT hybrids Traditional hybrid circuits with multiple balance networks can be used However hybrids with adaptive balance circuits based on echo canceler technology are becoming more common
The important methods for improving hybrid balance are as follows
Adherence to the loop design plans as discussed later in this section
7-14 SR-TSV-002275 BOC Notes on the LEC Networke 1994
Issue AprIl 1994 TransmIssion
Segregation between loaded loops nonloaded loops and treated loops those
equipped with transmission equipment such as repeaters or Subscriber Loop Carrier
with provision for automatic balance selection in the off-hook mode
Use of hybrids with adaptive sell-balancing circuits
Improved line-circuit balance is obtained by requiring that line circuits meet performance
specifications when connected to three specific test terminations Nonloaded loops are represented by 800 resistance in parallel with series combination of 0.05 ILF capacitance and 100 resistance For loaded loops 1650 resistance in parallel with
series combination of 0.005 pP capacitance and 100 resistance is used Finally treated lines are represented by 900 resistance in parallel with 2.16 jiF capacitance
Application of the proper balance network or adaptive balancing of the hybrid is function of the end-office switch Provision is sometimes made to add loss when necessary in the 4-wire portion of line circuits This is normally an interim measure to avoid singing when loop has severely deficient SRL
Balance in Remote Switching Units
Remote Switching Unit RSU or Remote Switching Module RSM controlled by an end office is considered to be part of its host office for transmission purposes The link between the remote and host has zero loss and in conjunction with the remote time-slot interchanger may contribute appreciable delay listener-echo path is formed since this link is provided on 4-wire facility To meet WEPL objectives on this path loop segregation with balance networks as previously discussed or adaptive hybrids should be used at the RSUIRSM
Echo-Control Devices
Echo-control devices normally cancelers are used in conjunction with impedance- balance loss control in the procedures and transmission-path to echo message network
They are used in cases of high end-to-end echo-path delay where loss values large enough to satisfy talker-echo objectives would result in unacceptable performance see
Section 7.11 Generally cancelers are required on long terrestrial trunks and on all trunks routed via satellite transmission facilities Cancelers also can be used to increase the return-loss performance in digital switch line cards
An echo canceler see Figure 7-6 utilizes an adaptive filter to model the near-end echo path tail circuit and predict the echo that will result from the reflection of far-end signal in the tail circuit replica of the predicted signal is subtracted from the actual echo signal and through an iterative process the canceler converges toward full cancellation
Because only the echo signal replica is subtracted in the sending direction signals originating at the near end pass through the canceler unimpeded
An important component in an echo canceler is detector that recognizes when near- and far-end signals are occurring simultaneously This double-talk detector inhibits the adaptive filter so that the near-end signal is not interpreted as an error signal Otherwise inappropriate adjustments would be made to the echo-path model return loss of as
7-15 BOC Note on the LEC Network 1994 SR-TSV-002275 Transmission Issue AprIl 1994
FIgure 7-6 Echo Canceler Application
circuit that the canceler much as dB may be required in the tail so can distinguish between returned echo and near-end signal thus permitting convergence to occur
Adaptive filters cannot achieve full cancellation and very small echo signals may not be canceled This can be due to nonlinear elements in the tail circuit residual suppressor typically center clipper is used to remove signals below specified threshold This of that the near-end suppressor may be inhibited during periods double-talking so signal is not modified
Echo cancelers can adapt only when signal is present There is training time typically 250-500 ma initiated by the first received signal During this interval echo will be returned to the far end The ability to converge is dependent on the amount of round-trip transmission delay in the tail circuit typical limit is 28 ins but longer options are available Accommodation of long tail-circuit delay can result in increased noise and convergence time Therefore it is advisable to position the canceler within
28 ins of the 4- to 2-wire conversion point
Echo cancelers use digital techniques and are most efficiently used where signals are transmitted via digroups 24 channels Because the canceler processes the signal bit integrity see Section 7.6.3 is not maintained Therefore provision should be made to disable cancelers whenever digital data signals are being transmitted
7.4.5 Slope
Some slope is desirable to provide margin against circuit instability singing at the edges of the voiceband Slope is less of an impairment to voice transmission than to voiceband data However low-frequency slope affects voice quality and excessive high-frequency slope reduces intelligibility of speech
7-16 SR-TSV.002275 BOC Notes on the .EC Networks 1994
Issue April 1994 TransmIssion
Slope is determined by measuring the loss of channel at several frequencies usually
404 1004 and 2804 Hz This is known as three-tone slope measurement Any increase or decrease in loss at 404 or 2804 Hz versus 1004 Hz is called slope Negative slope occurs if the loss at 404 or 2804 Hz is less than the loss at 1004 Hz
of end office-to-end office connection is determined the The slope an primarily by characteristics of the filters used in carrier channel banks digital remote terminals and digital switches The performance of these circuit elements is for the most part under the control of the equipment designer The slope contribution from subscriber loops excessive lengths of nonloaded cable pairs or bridged taps is under control of the outside-plant engineer
7.4.6 Influence of CPE on Perceived Voice Quality
The quality of an overall connection is dependent on the performance of the CPE at each end of the connection Low transmitter sensitivity excess receive gain distortion at high volumes uneven frequency response or excessive slope and other factors can result in poor performance ANSI Standard EIA 470-A-1987 specifies minimum standards for such equipment.1
7.5 Voiceband Data Transmission Impairments and their Control
Voiceband data performance depends on proper control of the impairments previously discussed as well as those covered in the following paragraphs
7.5.1 Impulse Noise
Impulse noise is defmed as any excursion of the noise waveform on channel that exceeds specified threshold level within certain time interval To minimize contributions due to the high ratio of peak to root mean square rmspower that is characteristic of message-circuit noise the threshold is set 12 to 18 dB above the rms value of the noise The impulse-noise level is designated to be that threshold at which the average counting rate is equal to five per minutes
of Since most impulse noise originates as transients from the operation relays and other electromechanical switches engineering rules and mitigative measures are aimed at shielding low-level carrier signals fromthe radiation of these transients Carrier-only cables shortened spans between repeaters and contact arc-suppression networks are some of the techniques used Electronic and digital central offices are relatively free of this impairment
7-17 SOC Notes on the LEC Networks 1994 SR-TSV-002275
Transmission Issue April 1994
7.5.2 Envelope Delay Distortion
Envelope Delay Distortion EDD is associated with distortion of received signal of caused by the unequal transit times the signals separate frequency components through transmission channel EDD gives rise to intersymbol interference in data transmission which causes increased sensitivity to background noise
An ideal channel would have phase versus frequency characteristic that is linear For such channel envelope delay which is defined as the slope of the phase/frequency characteristic would have constant value The performance of actual systems is evaluated by comparing envelope delay values throughout the frequency band
Envelope delay is approximated using difference measurement Test sets may use various frequency widths for this difference but the common value IEEE STD 743-
1984 is 166-2/3 Hz.3 Other widths give varying resolution of ripples in the envelope delay characteristic Narrower widths yield higher resolution but there is reduced accuracy
EDD sometimes called Relative Envelope Delay RED is the difference in envelope delay at given frequency compared to the envelope delay at reference frequency
Minimum envelope delay in telecommunications channels occurs in the vicinity of
1700 Hz Therefore envelope delay measurements are usually normalized to zero at reference frequency of 1700 Hz
In the network EDD is controlled in the design of codec filters and other apparatus and
switches Its especially by the use of digital thinks connected directly to digital importance has declined as analog trunk facilities and switches have become less common In data modems EDD effects are minimized by the use of fixed or automatic equalizers
7.5.3 Phase Jitter
modulation of transmitted It the Phase jitter is unwanted angular signal displaces zero crossings of the signal
the data-receiver Phase jitter impairs voiceband data transmission by reducing margin the of transmission against other impairments This impairment is controlled by design
data connections is equipment The end-to-end phase-jitter objective for intraLATA no more than 10 degrees peak-to-peak in the frequency band of 20 to 300 Hz and
15 degrees peak-to-peak in the band of to 300 Hz Individual digital carrier terminals are allotted 1.3 degrees Since phase jitter historically arose mainly in the carrier
carrier its supplies of single-sideband Frequency Division Multiplex FDM systems incidence has declined with the near-disappearance of such systems
Noise which can also perturb zero crossings can cause readings on phase-jitter measuring set even though no incidental modulation is present The design of test set can guard against this type of erroneous reading
7-18 SR.TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 TransmIssion
7.5.4 Nonlinear Intermodulation Distortion
Nonlinear elements in transmission equipment give rise to nonlinear distoition
Nonlinear distortion occurs when components generated from the transmitted signal add usually in an undesirable manner to that signal The primary concern is for nonlinear distortion within an individual voice channel as generated mainly in the PCM coding/decoding process
Nonlinear distortion specifications are usually stated in terms of intermodulation distortion Intermodulation products arising from nonlinear distortion interfere with the desired signal much as noise does However intermodulation distortion is more damaging than noise It reduces the error margin of data receiver and affects the automated accuracy of speech-recognition systems
The common method for measuring nonlinear distortion is called the 4-tone method
Four equal-level tones are transmitted at composite signal power level of13 dBmO data level Two tones are Hz apart centered at 860 Hz The other tones are 16 Hz apart centered at 1380 Hz The resulting test signal has an amplitude-density function similar to that of data signal At the receiving end the power averages of the second- and third-order intermodulation products are each compared to the composite 4-tone signal The ratios of the composite power to those of the products are called R2 and R3 respectively Care must be taken when measured values of R2 and R3 are large to ensure that noise does not cause false readings Procedures exist to determine the noise-only contributions so that readings can be corrected to indicate true distortion levels
Nonlinear distortion is controlled primarily in the design of equipment
7.5.5 C-Notched Noise
For voice transmission the noise that is heard during the quiet intervals of speech is most important This noise is the impairment that is quantified in the standard message- circuit noise measurement Transmission systems using compandors or quantizers exhibit increased noise in the presence of signal For voiceband data transmission the noise channel on the during active transmission and the corresponding signal-to-noise ratio are relevant
The effect of noise on data-modem performance depends upon the level of the noise relative to the level of the data signal The regulating amplifiers that are used in data sets to bring incoming data signals to an optimum level raise signal and noise equally Thus it is the signal-to-C-notched noise ratio of the incoming signal that determines data performance
To measure C-notched noise test holding tone at or near 1004 Hz is transmitted from the far end of the channel under test and then filtered out ahead of the noise-measuring set The level of the holding tone has traditionally been specified at two levels
16 dBmO for voice and 13 dBmO for data circuits The holding tone is removed by narrow-notch filter centered at the frequency of the tone hence the name C-notched noise This type of measurement is also referred to as noise-with-tone
7-19 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Transmission Issue April 1994
Figure 7-2 illustrates typical C-notched filter response
signal-to-C-notched noise ratio of at least 24 dB should be maintained on an end-to- end intraLATA data connection
7.5.6 SlIps
As explained later under Section 7.6.2.4 an impairment known as slip may occur if
is result will the deletion digital equipment not synchronized The of slip be or
repetition of one full frame 193 bits of information This can affect voiceband signals
being carried on digital channel
slip is rarely noticeable in voice transmission but it is likely to impair data
transmission because it causes discrete jumps in the phase of the received signal For
example the time interval occupied by slipped frame is exactly 125 microseconds For
data carrier frequency of 2000 Hz with period equal to 500 microseconds the
be 125/500 of full 90 sizable resulting phase step would cycle or degrees jump
7.5.7 Frequency Shift
If tone experiences change in frequency when it is transmitted over channel the
channel is said to give frequency shift or offset The shift can be measured by using
precise frequency source at one end of channel and frequency counter at the receiving
end Any difference is the frequency shift
Frequency shift is important in systems that use narrow-band receiving filters Frequency
shift cannot occur in digital facilities or switches but can take place in analog facilities
that use single-sideband suppressed-carrier transmission Frequency shift is controlled
by maintaining precise pilot signals and carrier frequencies on these systems
7.5.8 Slope
Slope has always been more important to voiceband data transmission than to voice
transmission Slope affects data and facsimile transmission but its role as an impairment
has decreased with the wide use of automatically equalized data sets
7.5.9 Customer Premises Equipment
Data modems may cause service degradation if their signal power is excessive Therefore this equipment should conform to an average long-term power requirement of
16 dBmO per channel However in applying this requirement it is possible to permit the idle periods between calls to compensate for somewhat higher power on channel
during active periods It has been established that the signal power during an actual call
should not exceed 13 dBmO averaged over any 3-second interval
7.20 SR-IS V.002275 SOC Notes on the LEC NetworksI 994 TransmIssion Issue April 1994
7.6 Digital Transmission
is 44Hz baseband voice In the analog network the fundamental transmission path voiceband are encoded to the channel For digital transmission signals according Each voiceband 255 law into 8-bit words at rate of 8000 words per second wps level channels channel is contained in one of twenty-four 64-kbps Digital Signal DSO
bit stream DS1 digroup that comprise the 1.544-Mbps Digital Signal level DS1 into in the digital hierarchy.5 signals are commonly multiplexed higher-rate signals
in the telecommunications network include transmission facilities Digital elements Cross-Connect and switching systems PCM channel banks Digital Systems DCSs the of automatic error multiplexers Maintenance of digital channels is simplified by use
and the to test the rather than each monitoring on digital facilities by ability digroup channel
facilities Substantial savings can be realized by terminating digital transmission directly
in This dedication of digroups to onto digital switches digroups normally requires circuits to message trunk service with all unswitched special-services being assigned
other digroups
services Alternatively use of the nail-up function in the digital switch for special is to would allow mixed digroup to be terminated directly Another possibility separate mixed means of DCS prior to the special-services circuits from the digroup by termination on the switch
7.6.1 SynchronizatIon
between in the network Synchronization ensures that the bit streams digital equipment and are DS facilities within operate at the same frequency phase-aligned are to synchronization network sector usually corresponding to LATA synchronized
centralized timing source Synchronization within building is accomplished by tinting
all digital equipment from one source the Building-Integrated Timing Supply BiTS
is contained in Section 11 complete description of intraLATA digital synchronization
7.6.2 CharacteristIcs of Digital Transmission
7.6.2.1 Error-Free Seconds
that does not contain bit errors An Error-Free Second EFS is any 1-second interval any
7.6.2.2 Bit Error Ratio
referred to as Bit Error Rate is the fraction of The Bit Error Ratio BER sometimes stream errored bits relative to total bits received in the transmitted digital
7-21 BOC Notes on the LEC Networks 1994 SR-IS V.002275 1994 Transmission Issue April
7.6.2.3 Severely Errored Seconds
Severely Errored Second SES is 1-second interval during which the BER is greater than or equal to iO at DSO or DS1 transmission rates This corresponds to greater than
than bit at the 64 bit errors over 1-second period at the DSO rate or greater 1544 errors DS1 rate
7.6.2.4 Slips
transmission impairment known as slip also called controlled slip can occur if switch receives digital equipment is not synchronized As an example suppose digital in other DS signals that differ in frequency from the internal rate of the switch words frequency offset exists An overflow or underfiow of information will eventually occur frame of This results in slip which is the deletion or repetition of one entire 193 bits in information These modifications to the digital stream can cause significant errors digital data transmission
7.6.2.5 Phase Hits
The switching of digital transmission facilities or multiplex equipment for example from working to standby element can cause rapid change in phase called hit on the transmitted signal Receiving synchronizing equipment is designed to buffer
facilities changes in incoming phase However the switching of transmission may cause between the hit directly on the transmitted signal as result of difference in phase working and standby facilities
7.6.2.6 Timing Jitter
of The random accumulation of small timing errors in the clock circuits of string digital
lead variations in the of This jitter regenerators can to timing digital signal timing into the voice can cause digital errors and in the extreme introduce distortion signals carried on the digital channels
7.6.3 Bit Integrity
network without The capability of transmitting bit streams through the any change avoid jreserving bit integrity is benefit of end-to-end digital connections To
is inserted on all- intermediate digital processing which destroys bit integrity loss end where conversion occurs digital connections at the receiving only digital-to-analog need to have the Devices such as echo cancelers that utilize digital processing capability of being disabled when necessary to preserve bit integrity
7-22 SR-TSV-002275 BOC Notes on the LEC Networks 1994 TransmIssion Issue AprIl 1994
7.6.4 Clear-Channel Capability
With conventional digital transmission the eighth bit of every sixth word is robbed
Where is carried other for purposes of transmitting signaling information signaling by means such as with Common Channel Signaling CCS bit rate of 64 kbps is available
services This is referred to for Integrated Services Digital Network ISDN as DSO
Clear-Channel Capability DSO CCC
into In order to obtain transparency in DS signal DS CCC it is necessaiy to take account the ones-density requirement This requirement is imposed by the clock- methods recovery circuits in digital line repeaters and other regenerators Two coding of successive with another that plans are used to replace string eight zeroes string Substitution provides sufficient ones These methods are Bipolar with 8-Zero B8ZS and Zero-Byte Time-Slot Interchange ZBTSI
with of ones In the B8ZS method eight successive zeroes are replaced unique pattern containing Bipolar Violations BPVs The normal bipolar coding nile sometimes be followed referred to as Alternate Mark Inversion requires positive pulse to by
vice-versa.6 be between the At the negative pulse and There may zeroes pulses
of is restoration of the receiving end the unique pattern BPVs detected triggering
is that associated original group of eight zeroes consideration with this method digital equipment must be optioned to recognize the unique pattern and not treat it as BPVs
caused by errors
for all-zero octets The ZBTSI method involves buffering the bit stream and searching
words that in combination with their adjacent words result in violation of the ones-
the all-zero octet is and density requirement When this condition is found flagged
replaced by an inserted address code containing sufficient ones to meet the requirement
restored its At the receiving end the flag and code are recognized and the word is to
original all-zero state
detection An advantage of the ZBTSI method is that it does not interfere with error
violations is techniques that are based on the presence of bipolar disadvantage increased transmission delay caused by the necessary buffering Delay considerations in network are responsible for B8ZS being the preferred method long-term plans
7.7 Digital Data Transmission
various over both dedicated line and Digital data can be transmitted at speeds private for intraLATA service as well switched facilities These capabilities which are offered
as for LATA access are discussed in the following paragraphs
7.7.1 DedIcated Digital Services
baseband data transmission via dedicated Digital Data Special Access Service provides
facilities Full duplex synchronous digital transmission at bit rates of 2.4 4.8 9.6 19.2 channel also be 56 and 64 kbps is available An additional lower-speed secondary may
7-23 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue 1994 TransmIssion AprIl
in with the provided along with all but the 64-kbps rate These channels operate parallel monitor his/her own primary data channel and are used by the customer to control or network
Service transmission at rates of High-Capacity Digital Special Access provides digital used 1.544 Mbps and higher The DS3 rate 44.736 Mbps is the most commonly higher and DS4NA are rate although DS1C 3.152 Mbps DS2 6.3 12 Mbps 139.264 Mbps
available in some instances
The LECs offer these digital services under various trade names performance
in local tariffs Where access is involved performance specifications are provided LATA of the connection can be found in Beilcore technical specifications for the access portion Access Service references Transmission parameter limits for Digital Data Special 64 Data Access Service kbps and under can be found in TR-NWT-000341 Digital Special Combinations.7 For Transmission Parameter Limits and Inteiface High-Capacity
in TR-INS-000342 Digital Digital Service requirements are contained High-Capacity and Combinations.8 Special Access Service Transmission Parameter Limits Interface
7.7.2 Switched 56 Kbps Services
for end-to-end Switched 56 kbps services provide circuit-switched transport capability
this service has been full-duplex 56-kbps digital transmission For some time provided under the umbrella name of Public Switched Digital using end-to-end digital connections of the ISDN bearer Service PSDS More recently the service is being provided as one services
Services Generic feature requirements for PSDS are contained in TR-TSY-000534 Data
Public Switched Digital Service.9
Standard Three end-user interface arrangements for PSDS are defmed in ANSI T.EAJEIA-596-19930
line rate of 56 The 4-wire access using AMI digital transmission at loop kbps
interface for this access technology is designated Type in TIA/EIA-596-1993
of 144 2-wire access using Time-Compression Multiplexing TCM at line rate
is II kbps The interface for this access technology designated Type
uses 2-wire access using TCM at line rate of 160 kbps This access technology Type ifi interface
in each direction Sufficient time is allowed In TCM bursts of digital signal are transmitted alternately of burst in the other between bursts to ensure that the signal has been received prior to transmittal for at direction Use of line rate that is significantly higher than 56 kbps allows full-duplex operation 56kbps
7-24 BOC Notes on the LEC Networks 1994 SR-TSV-002275 TransmissIon Issue AprIl 1994
Standard TIA/EIA-596-1993 In addition to defining the three types of interfaces ANSI for Network Channel Terminating provides technical and functional requirements between NCTE and Data Terminal Equipment NCTE specifications for interfaces and maintenance requirements for Equipment DTE and end-to-end compatibility described in the connection to PSDS The three access arrangements are briefly PSDS architectures can be found in following paragraphs More information on
Section 14 of this document
7.7.2.1 Type PSDS Access
Data Access Service This access arrangement is similar to that used for Digital Special connection via 1A ESS analog switch Later An early application provided PSDS connections via various manufacturers digital switches applications allow PSDS
7.7.2.2 Circuit-Switched Digital Capability
is feature offering that provides PSDS Circuit-Switched Digital Capability CSDC for served the 1A ESS switch capability via 2-wire Type access customers by in 200-bit bursts at bit rate of 144 kbps Loops Data is transmitted using AMI coding
and loss at 72 kHz the half-bit rate Both are limited in length delay considerations be taken into account the loss of the loop and the effects of bridged taps must
is at the 1A ESS end office to provide full Special line terminating equipment required the trunk side On the trunk side the data signal is duplex path through the switch to End-to-end is via digital placed on DSO channel of DS1 or higher facility muting of the bits of each byte must be trunks and tandem offices The integrity data-carrying echo cancelers and avoiding maintained to the far end This is accomplished by disabling
digital pads or other forms of digital processing
contained in ANSI Standard TIA/EIA In addition to the Type II interface information 596-1993 information on CSDC service can be found in TR-880-22135-84-01 Circuit
Network Access Specifications.11 Switched Digital Capability Interface
7.7.2.3 DATAPATHTM
is utilized on two-wire loop to DATAPATh service is similar to CSDC in that TCM In this however the TCM bit rate is 160 provide access Type ifi to the end office case via Northern Telecom DMS-100 digital switch The kbps and the service is provided
ESS is trademark of ATT
of Northern DATAPATH is trademark Telecom
trademark of Northern Telecom DMS- 100 is registered
7-25 BOC Notes on the LEC Networks 1994 SR-TSV-002275 1994 Transmission Issue AprIl
channel 160-kbps TCM rate provides full 64-kbps data channel with an 8-kbps signal for control and maintenance functions It should be noted however that end-to-end
is without clear-channel transmission transmission of 64.-kbps data signals not possible addition the facilities in the network Such facilities are not provided for PSDS In to
Type Ill interface information contained in ANSI Standard 11AIEIA-596-1993 information on DATAPATH service can be found in TR-EOP-000277 DATAPATH1 Network and Network Access Interface Specification Switched Compatibility Public Switched Performance Specifi cations for 2-Wire Connection to Digital Network12
7.7.2.4 Interworking of PSDS Technologies
The end-user equipment for PSDS must be compatible with the protocol used by the serving switch However there are no restrictions on calls between end-user equipment that employ any of these technologies As noted above end-to-end connections must and switches Where inband is used PSDS consist solely of digital facilities signaling trunks calls must be routed via dedicated trunk groups consisting only of digital class mark terminating on digital switches This is because there is no unique traveling facilities to identify PSDS call throughout the network to ensure routing by digital
With deployment of Signaling System SS7 PSDS call routing wifi not require dedicated trunk groups
7.7.2.5 Switched 56 Kbps as an ISDN Bearer Service
and One of the circuit-mode bearer services defmed for both the ISDN Basic Rate from 56 Primary Rate Interfaces is Unrestricted Digital Information Rate Adapted carried within B-channel The ISDN end- kbps The 56 kbps of user data is 64-kbps is not user equipment provides rate adaption which ensures that the all-zero octet the transmitted Although the network may employ digital facilities without CCC received bit stream of user data at the terminating end is identical within performance end- limitations to the transmitted bit stream at the originating end in other words the to-end connection maintains bit integrity
Data 7.7.2.6 Interworking Between PSDS and ISDN Switched 56 Kbps
to it will be to With the conversion of trunk signaling from multifrequency SS7 possible trunk and these route PSDS and ISDN 56-kbps calls over shared SS7-supported groups calls will be able to interwork SR-NWT-002598 Clarification of the Requirements for
various Beilcore documents Public Switched Digital Service PSDS13 references the this to take that provide the requirements that will allow interworking place
7-26 SR-IS V-002275 BOC Notes on the LEC Networks 1994 TransmissIon Issue AprIl 1994
7.7.3 Switched 64 Kbps Service
Another ISDN bearer service defined for both Basic Rate and Primary Rate Interfaces is The essential characteristics of the Unrestricted Digital Information 64-kbps CCC
service are that there are no restrictions on the users 64-kbps data stream and the
received bit stream is identical within performance limitations to the transmitted stream
That bit is maintained at the originating demarcation point is integrity
7.7.4 ISDN Switched DS1/Switched Fractional DS1
Switched Fractional DS SWF-DS is family of multirate services that provides the bandwidth of ISDN end user with the ability to obtain CCC for on demand Speeds of 64 kbps to 1536 kbps can be accessed SWF-DS1 is offered to the end user at rates and NX64 kbps where 24 NOTE For N6 384 kbps N23 1472 kbps N24 1536 kbps channels are designated HO H1O and Hi respectively
7.7.5 Switched Digital Services Performance
for intraLATA As with Digital Data Services DDSs performance specifications
is switched digital services are provided in local tariffs Where LATA access involved
for the can be found in Beilcore technical performance specifications access portion references Transmission parameter limits for ISDN-based switched DDSs can be found Transmission in TR-NWT-000938 Integrated Services Digital Network ISDN Network
Inteiface and Performance Specfications.4
7.8 Transmission Aspects of Switches
7.8.1 ComparIson of Analog and Digital Switches
basic there are Although analog and digital end offices provide the same functions fundamental differences in their designs Table 7-2 compares features that relate to of switches of the transmission and signaling performance of the two types Some for the use of differences are specific to particular manufacturers switch example
floating ground versus ground-referenced batteiy supply
7-27 BOC Notes on the LEC Networks 1994 SR-TSV002275 1994 Transmission Issue AprIl
Table 7-2 Transmission Characteristics Analog versus Digital End Offices
Parameter Analog Office Digital Office
LOOP sauei U1IIY
Ground-Referenced or Floating Battery Feed Ground-Referenced
Current Limiting of Loop Current Simple Resistor Simple Resistor or Regulator
Few and Short or None Open Switch Intervals Many and Long
1600-2000 Loop Limit 1500-1600
Current to CPE Loop Limited by Signaling Supervision
Transmission Aspects
Cross-Office Loss 0.3-1.5 dB not controlled 0-7 dB set via translations
analog or digital padding
Test Access Loss 0.3-0.6 dB dB
loss 200 Hz and 3.4 kHz Frequency Response High loss200 Hz High
500 and 2000 Hz Envelope Delay Distortion Minor 300 Hz Some
variable 16-19 dBrnC constant Noise Message to dBmC highly
60 dB dB Signal-to-CNN Ratio Very high approx approx.35
42 dBrnC Impulse Noise SXS59 dBmC Threshold for Crossbar 54 dBrnC Counts inS mm Electronic 47 dBrnC
Metallic Path None Possible Path Frequency Shift None Possible Digital
Phase Hits None Possible Possible on lnterentity Calls
if Sync Net Fails
Coder Overload Overload Point approx 20 dBm Saturation 3.17 dEmO
in Inductors
variable Echo Delay 0.2 ms fixed 1.5 ins
Pad and/or Variable Pad Control in Analog Pad Controlled by Class Digital Analog
Centrex Networks of Service or Translations Amplifier Controlled by Translations
DLC Interface Tip Ring Tip Ring or Integrated OS1
Cross-Office Path Physical Wire Contacts Electronic Hybrid Coder
Repeat Coils Relays Decoder Hybrid Memories Tone Sources Analog Oscillators Read-Only
Processors Tone Receivers Analog Filters and Rectifiers Digital Signal
Per-Frame Inverters Ringing Sources Common Generator
Metallic Test Access for Yes Yes
Loop Test System
Trunk Interfaces IF Yes Not in Some Designs
DS-1 Only with DCT Frame Yes
In Some Nail-Up of Special Services No
7-28 SR-TSV002275 BOC Note on the LEC Networks 1994 Transmission Issue April 1994
7.8.2 DIgital Switch Distortion Performance
Bit robbing discussed in Section 7.6.4 results in 7-5/6 bit code that gives signal-to- distortion ratio approximately 1.8 dB lower than that for full 8-bit signal It is typical bit stream on call switched through digital tandem office for signaling on the outgoing of frame that differs from the frame used on the to use the eighth bit-position incoming trunk that or echo bit stream This can also occur on digital passes through DCS an disassociated bit canceler It is likely that the output will be 7-4/6 bit code With this
borrowing the result after five tandem switching stages could be equivalent to coding with bits never fewer This would cause an additional 4.2-dB degradation of signal-
to-distortion performance
In practice the chance of only seven bits being used is relatively small given reasonable number of switching stages Figure 7-7 shows the relative probabilities of
various numbers of coding bits being used versus the number of intermediate bit-
with three of the relative chances are borrowing stages For example stages switching
7-3/6 57 It should be noted 7-5/6 bits percent 7-4/6 bits 40 percent and bits percent that with DSO CCC transmission this problem will not exist
100
.0
.0
50
12 15
Switching or DCS Stages
Figure 7-7 Probable Numbers of Coding Bits Used
7-29 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Transmission
7.9 Adaptive Differential Pulse-Code Modulation Technology
is method for encoding Adaptive Differential Pulse-Code Modulation ADPCM digital fewer bits channel than PCM of analog signals that requires per
the difference between With ADPCM only 4-bit error signal is sent denoting and the actual value of The international standard ADPCM predicted value signal to 64 for PCM ADPCM is system uses 32 kbps per voice channel as compared kbps in international trunks not used widely in exchange carrier networks but is quite common
and private networks
between and ADPCM This makes ADPCM transcoder converts signals digitally PCM switches and channel banks transmission compatible with PCM terminals such as digital lines on one side and one Typically the transcoder interfaces with two PCM-DS 44 of the 48 PCM channels ADPCM-DS line on the other In some transcoders only slots used for and maintenance are available The remaining time are signaling
information
less in with PCM The performance of ADPCM for speech is only slightly comparison be detected with ordinary test equipment that measures The presence of ADPCM cannot tandem ADPCM bandwidth idle noise C-notched noise or slope However fewer
encodings can be tolerated as compared to PCM encodings
in the of ADPCM that be encountered Application rules limiting number encodings may Network the network are provided in ANSI Standard Ti .501-1988 Performance Pulse-Code Modulation.15 Tandem Encoding Limits for 32 Kbitls Adaptive Differential
is Since the ADPCM algorithm is based on characteristics of voice signals performance Normal of Dual-Tone somewhat poorer for voiceband data applications multifrequency but all modem Multifrequency DTMF or single-frequency signaling are not affected terminals to some extent modems and digital facsimile signals are degraded Many of 4800 half or 2400 bps full duplex by frequency operating at data rates bps duplex
all The rule is to limit the division operate poorly or not at over ADPCM general three An tandem ADPCM number of asynchronous tandem encodings to asynchronous the must through an encoding occurs when the connection is analog when signal pass for limit three ADPCM allows some margin analog switch for example of encodings recommended the ITU-T formerly the CCiTt impairment from other factors As by
the international limit is four
the to no it is to convert ADPCM PCM To pass through digital switch necessary only standard ADPCM contains synchronous analog connection is required The algorithm is converted to that occurs when the ADPCM signal coding adjustment such no penalty PCM and back without an analog interface
and bit streams are not disturbed by errors However this assumes that the ADPCM PCM such as digital loss Such bit-robbing for signaling or by digital signal processing since most connection would be rare in the United States in pre-ISDN environment bit with bit-shared PCM digital tandem without integrity digital switches interface ranging between negligible and that of an will generally give an ADPCM degradation
7.30 LEC Networks 1994 SR-TSV-002275 BOC Notes on the TransmissIon Issue AprU 1994
of is small for bit-shared PCM but to that asynchronous connection The penalty equal an asynchronous encoding if digital loss is used
7.10 Asynchronous Transfer Mode Technology
transmission method that Asynchronous Transfer Mode ATM is flexible digital need for allows different kinds of services to be carried in one network without overlay or networks for each service This is accomplished by putting the digitized voice data
of called cells Cells are video signal into standard fixed-length packets bytes cells be assembled from the bit stream of the source call or service These may
intermixed with cells from other services Cells are routed through the network at ATM and switching points At the destination the cells for each service are sorted collected each service disassembled into bit stream appropriate to
call cells for Each cell is independent of other cells even those of the same However later There are no time given call are routed over the same path as discussed assigned such as Time Division slots as there are in synchronous systems Multiplex TDM
Hence the name Asynchronous Transfer Mode
7.10.1 ATM Cells
of 53 An ATM cell as standardized by the 1TU-T formerly the CCiTT consists bytes header and information field The header Each cell is partitioned into 5-byte 48-byte field contains overhead information for functions such as routing The information may
also contain some overhead The advantages of fixed-length cells over variable-length hardware and software for cell cells are smaller cell delay variation and simpler The cell is processing at sources nodes and destinations 53-byte compromise and short cells which between long cells which are more efficient for video and data
have less delay for voice
7.10.2 ATM Cell Assembly and Disassembly
into cells Cell Cell assembly consists of loading the source bit stream ATM disassembly 7-8 illustrates cell consists of unloading the cells into the destination bit stream Figure Constant Bit and Variable Bit Rate assembly where two types of service Rate CBR DS3 connection CBR services such as voice transmission VBR are combined over data in cells be created at fixed rate while VBR services which transmit require to followed three non-CBR cells bursts do not In the example one CBR cell is created by be to that CBR services will always Access algorithms can used ensure delay-sensitive and can be when data is VBR services are generally more delay-tolerant get cell ready available VBR services can use all of the permitted to wait if cell is not immediately the VBR service has cells that are not being used by the CBR service In this example
7.31 SR-IS V-002275 BOC Notes on the LEC Networks 1994 Issue 1994 Transmission April
Cells supporting CBR services Adaptation occur at fixed rate Layer
AdaptaUon
DS3 Connection
Cells supporting VBR
services occur in bursts
Service Adaptation Switching and Transmission Layer Layer
Ky Bit Rate used for VBR Service CBR Constant ______Cells VBR Variable Bit Rate Cells used for CBR Service
Unused Cells
Figure 7-8 Combining CBR and VBR Traffic Using Cell Switching
cells Unused cells maintain transmitted burst of data requiring only two empty cells periodicity of the CBR
7.10.3 ATM Switching
and The switching methodology for ATM cells differs from those used in analog digital switches
switch for Analog switches reserve and nail up physical path through the given switches the switch in call for the duration of the call Digital reserve path through have fixed bandwidth the form of designated time slot In either case the path must switch to the bandwidth to be switched Thus if switch can capability equal highest for narrowband if switch is efficient for broadband signals it is inefficient signals switch broadband narrowband signals it cannot readily signals
These unused cells could be used to carry other VBR services
7-32 SR.TSV-002275 SOC Notes on the LEC Networks 1994
ISSUe AprIl 1994 TransmissIon
ATM switches route cells independently according to their header address However
once path is determined for given call all subsequent cells for that call follow the connection same path Services of all bandwidths may share the same physical it Cells service can use whatever bandwidth it needs and dynamically vary from
various routes are queued and merged or routed when they reach the front of the
queue in process called statistical multiplexing
ATM does not provide dedicated connections for calls Rather ATM provides virtual
connections on virtual paths and on virtual channels
7.10.4 ATM Transport
Between ATM switching nodes ATM cells may be carried on DS1 DS3 or Table 7-3 shows the Synchronous Optical Network SONET facilities see Section 14 raw bandwidth of SONET channels the bandwidth available to ATM and the bandwidth
available to ATM cell information fields payload that is available to application with bit rate layers above the cell layer Bandwidth is synonymous or speed
Table 7-3 Bandwidths for SONET Transport Mbps
Facility Line Rate Available Rate Available Rate
for ATM cells for Applications
STS-l 51.84 49.536 44.863
STS-3 155.52 149.76 135.632
STS-12 622.08 600.896 544.208
accommodated in Following are illustrations of how different bandwidths are ATM
transport
loaded into cells that occur single 64-kbps voice or voiceband data channel can be
with approximate period ms or at rate of about 167 cells per second in the ATM
cell stream
1.544 Mbps DS1 can be loaded into cells that occur with approximate period 1/4 cells in the ATM cell ms or at rate of about 4000 per second stream
44.736 Mbps DS3 can be loaded into cells that occur with approximate period 8.6 cells second in the ATM cell stream p.s or at rate of about 116000 per
available for cells of other calls or In any of these cases the intervening intervals are services NOTE Cells for CBR services occur in the ATM cell stream with cell
to the cell delay which is discussed period approximately equal assembly/disassembly below
7-33 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Transmission Issue April 1994
7.10.5 ATM Delay
7.10.5.1 Delay Associated with Cell Assembly and Disassembly
Since the source bit stream is at lower bit rate than the SONET Synchronous Transport
Signal level STS-N bit stream the cell assembly process introduces delay The assembler cannot form cell until 48 bytes have arrived Similarly the disassembler can
with the lower bit rate of the destination bit only emit bytes at rate that is compatible stream
For example for DSO 64-kbps voice or voiceband data as the source the one-way delay for loading 48 bytes into cells is about ms
48 bytes bits/byte 64 kbps ms
As another example for DS circuit emulation as the source that is the carrying of DS on ATM cells the one-way delay for loading 48 bytes into cells is about 1/4 ms
48 bytes bits/byte 1.544 Mbps 1/4 ms
Finally for DS3 circuit emulation as the source that is the carrying of DS3 on ATM cells the one-way delay for loading 48 bytes into cells is about 8.6 p.s
48 bytes bits/byte 44.736 MbpS 8.6 p.s
7.10.5.2 Delay Associated with SONET Rate Conversion
and There is similar delay mechanism when STS-1 cells are converted to STS-3 cells
cells but the back again or when STS-3 cells are converted to STS-12 and back again The for conversion between amount of delay has negligible effect on performance delay
STS-l and STS-3 is about 7.4 Jis
48 bytes bits/byte 51.84 Mbps 7.4 p.s
The delay for conversion between STS-3 and STS-12 is about 2.5 p.s
48 bytes bits/byte 155.52 Mbps 2.5 p.s
7.10.5.3 Delay Associated with Jitter Removal
Due to contention at queues accompanying such functions as merging of bit streams at
cell concentrators and cell switches the cells for given source get randomly jittered
their in time The of the jitter depends on with respect to original positions spread of traffic that cell several factors including the number of such queues and the amount must contend with at each queue
of the while VBR services do CBR services require restoration of the periodicity bytes removal buffer not Restoration of CBR services is accomplished by means of jitter
cell The removal buffer just prior to or in conjunction with disassembly jitter
7-34 LEC Networks SR.TSV-002275 BOC Notes on the 1994 Transmission issue April 1994
to introduces delay equal to the buffer length which by design is approximately equal the width of the delay variation distribution
7.10.5.4 Total ATM Delay
removal buffer in are in The assembly/disassembly delay and jitter delay ATM transport
contribution echo is addition to the delay of digital systems The ATM to path delay
total for voice for twice the one-way assembly/disassembly delay 12 ms 64-kbps the removal buffer at each end can be several ins example plus sum of jitter delays this which necessitate additional echo control for This is significant increase in delay may for echo control has not been standardized voice transport on ATM method yet
7.10.6 TransmissIon Errors and Cell Loss
introduce Transmission errors in the underlying SONET transport facility layer will of errors into cell header or into the cell information field or perhaps both in the case
burst errors The effect of header errors and information field errors is different An
information field error will result directly in single error in the decoded bit stream in the header error may result in lost or misrouted cells and 48-byte long discontinuity decoded bit stream similar to frame insertion or omission slip in TDM systems
due Cell loss can also result from buffer overflow at queues at ATM switching nodes to contention among cells of various calls or services at times of high traffic In addition buffer when cell cell loss can result from buffer overflow at jitter removal delay The of the buffers is trade variation delay jitter exceeds the buffer capacity design
off between cell loss cell delay and buffer memory requirements
7.11 End-to-End Performance
call is based an Customer perception of the transmission quality of telephone on assessment of end-to-end performance This performance is composite of the in Section performance of each portion of the end-to-end connection described 7.2.1 and are Moreover voice performance parameters for example loss noise echo
interrelated in complex manner The following paragraphs describe the methodology in used to arrive at performance estimates for connections in existing networks or new
architectures where the changes may be relatively minor or global
7.11.1 Grade of Service
means Estimates of end-to-end performance are obtained in terms of customer opinion by of models involved one characterizing the of modeling techniques Two types are
studied the other relating customer to the performance of the network being opinion Customer models are presence/magnitude of various performance impairments opinion field in which combinations of based on subjective tests conducted in the or laboratory
7-35 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Transmission
These impairments with controlled magnitude are presented to subjects subjects judge
each combination it in one of five categories excellent good the quality of by placing fair poor or unsatisfactory
Grade of Service GOS combines the distribution of customer opinions with the to obtain the distribution of telephone plant performance parameters expected percentage to combine the of customer opinions in each of the five categories It is common practice Good Or Better good and excellent percentages to arrive at Percent GOB which combines rating Alternatively the Percent Poor Or Worse POW rating used These terms are also the poor and unsatisfactory categories is sometimes used for customer opinion models as discussed in the following paragraphs
7.11.2 Customer Opinion
of The effects of loss noise talker echo and listener echo on customer opinion telephone
connections are discussed in this section
7.11.2.1 Perception of Loss
for network In this Figure 7-9 shows the effect of loss on customer opinion an analog study the end office-to-end office loss was varied over range of 20 dB for short- function of medium- and long-mileage calls Customer %-GOB ratings are plotted as loss to this loss It can be seen that customer opinion improves with increased up
maximum value and then declines as the loss continues to increase The maximum of calls values are approximately and dB respectively for the three categories the Via Net-Loss Also indicated is the range of losses that resulted from application of VNL Plan to analog networks see Section 7.12.1.1
7-10 The curves have similar Study results for digital network are shown in Figure each of call The factors shapes again indicating an optimum value of loss for category discussed in Section that cause the curves to differ from those for an analog network are 7.12
7.11.2.2 Loss/Noise
estimated The effects of connection-loudness loss and message-circuit noise are by of constant GOB are means of loss/noise subjective-opinion models Contours tests For low values of shown in Figure 7-11 for specific set of loss/noise subjective
is controlled noise the model indicates that the percentage of calls rated good or better values of noise both loss and noise affect the rating primarily by loss For higher
7-36 Note the LEC Networks 1994 SR-TSV-002275 BOC on Transmission Issue April 1994
100
90
80
70
60
50
10 15 20
End Office-to-End Office Loss dB
Office-to-End Office Loss Network Figure 7-9 Customer Perception of End Analog
100
90
80
70
60
50 10 15 20
End Office-to-End Office Loss dB
of End Office-to-End Office Loss Digital Figure 7-10 Customer Perception Network
7-37 SR-IS V-002275 BOC Notes on the LEC Networks 1994 1994 Transmission issue April
25
20 C/ C/
C/ 15
-J 10
15 20 25 30 35 40 45
NOISE IN dBmC INPUT TO SET
Figure 7-11 Loss/Noise Grade of Service
7.11.2.3 Talker Echo
the and of The amount of annoyance caused by talker echo depends on amplitude delay model It can be seen that the the echo Figure 7-12 shows talker-echo opinion rises with amount of echo path loss needed to achieve given talker-echo rating TOLR and ROLR increased echo delay The acoustic echo path loss includes the see the to the reflection Section 7.4.1 of the telephone set/loop the electrical loss from loop the reflection For with 500-type telephone point and back and the ERL at point loops of about dB and standard deviation set the sum of the TOLR and ROLR has mean of about 3.5 dB
7-38 SR-IS V-002275 BOC Notes on the LEC Networks 1994
Issue AprIl 1994 TransmIssion
7.11.2.4 Loss/Noise/Talker Echo
combined loss/noise/talker echo opinion model is shown in Figure 7-12 These in 7-12 results are for specific combination of loss and noise However just as Figure decreases and/or the echo as the acoustic echo path loss of connection path delay
increases decrease occurs in the percentage of customers rating the connection good or
better
7.11.2.5 Listener Echo
echo alone and combined Figures 7-12 and show opinion models for listener loss/noise/listener echo respectively The ratings are plotted as function of WEPL see Section 7.4.4 The effects of changing the echo path loss and/or the echo path delay are
similar to those for talker echo
7.11.3 Network Performance
Estimated performance for intraend office connections connections involving customers served by the same end office is shown in Figure 7-13 The estimates were obtained by
determining the distribution of loudness losses for connections via analog end offices
that is assuming fixed value of noise and applying the subjective opinion model to the
loss/noise values
Performance estimated for interend office connections designed under the VNL Plan is loudness-loss also shown in Figure 7-13 fixed value of dB of loss was added to the
distribution that was used for the intraend office connections to obtain loudness-loss end distribution applicable to interend office connections The approximate average
office-to-end office loss for nonmetropolitan connections in the older analog network was dB
The performance curves in Figure 7-13 are results of particular subjective opinion
database and connection performance models based on loss/noise assumptions for different database would result in specific type of network Use of opinion probably that the different values of GOB for this network However it would be expected remain about the shape and relative placement of the performance curves would same architectures The point is that in evaluating the performance of two or more common values the relevant opinion model is used The resulting differences in performance are
rather than the absolute values obtained
7-39 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Transmission
MODEL TALKER ECHO OPINION MODEL LISTENER ECHO OPINION
99 99
95 95
80 80
50 50
20 20
10 15 -5 15 35 55
ECHO PATH LOSS IN dB ACOUSTIC-TO-ACOUSTIC TALKER WEIGHTED
ECHO PATH LOSS IN dB
LOSS/NOISE/TALKER ECHO LOSS/NOISE/LISTENER ECHO OPINION MODEL OPINION MODEL
99 99
95 95
80 80
50 50
20 20 Ui
Ui a-
10 15 -5 15 35 55
ECHO PATH IN dB ACOUSTIC-TO-ACOUSTIC TALKER WEIGHTED LOSS
ECHO PATH LOSS IN dB
Grade of Service Figure 7-12 Loss/Noise/EchO
7-40 BOC Notes on the LEC Networks 1994 SR-IS V-002275 Transmission issue April 1994
99.99
99.9
99.5 99 98
I- 95
-J 90
80
70
60
50
40
30
C/ 20
10
Li
0.5
0.1
0.01 101520 25303540455055 6065707580859095100
PERCENT GOOD OR BEUER
Distributions Figure 7-13 Grade-of-Service
7-41 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Transmission
7.12 Network Transmission Design
networks as well as the The various transmission loss plans that relate to intraLATA
in this section methods for implementing the desired loss are discussed
7.12.1 Network Transmission Plans
has transmission plans have been developed As the telephone network evolved various the best transmission performance on the largest with the purpose of providing possible economic constraints These plans are majority of telephone calls within appropriate discussed in the following paragraphs
7.12.1.1 Via Net-Loss Plan
The VNL Plan was developed in the early 1950s for nationwide totally analog the lowest loss in each connection network.16 The objective was to provide possible The was developed using commensurate with satisfactory talker-echo performance plan the talker echo It took into account the results of studies indicating user tolerance to in trunk losses from number of trunks in connection the expected random deviations
distant end office design values and the expected ERL at the
of the trunk The VNL Plan assigned loss to trunk based on the amount round-trip delay of the of as well as the was expected to contribute Since delay is function type facility taken into account To ensure minimum trunk length both of these characteristics were trunk to tandem- value of loss on all connections each toll-connecting similar
loss of 2.5 dB in addition to the applicable VNL connecting trunk was assigned maximum connection loss of approximately 11 dB was permitted for round-trip delays echo were deployed approaching 45 ms For greater delays suppressors/cancelers
loss have been to modern The VNL Plan is rarely used as more recent plans applied trunks used in intraLATA applications networks Table 7-4 gives VNL values for carrier
Table 7-4 VNL and ICL Values for Trunks on Carrier Facilities
Trunk Length nil ICL VNL dB5
0-165 0.5 166-365 0.8
366-565 1.1
Any length with echo canceler 0.0
0.0015 Average Length 0.4 dB VNL Via Net Loss ICL Inserted Connection Loss
7-42 SR-TSV-002275 BOC Notes on the LEC Networks 1994 TransmissIon Issue AprIl 1994
7.12.1.2 Fixed-Loss Plan
network because of the that The VNL Plan is not well suited to an all-digital requirement
loss be inserted into each trunk Satisfying this requirement would entail
loss insertion and or Decoding of the digital signal followed by analog recoding
level Use of digital pads to lower the ultimate analog signal
both of these introduce In addition to increasing the cost of facilities techniques
transmission impairments Decoding and encoding add quantizing noise to the signal in the adds noise and decreases the while digital processing to insert loss analog signal
ratio With either bit Section 7.6.3 is lost signal-to-distortion technique integrity see
The Fixed-Loss Plan was developed to address the needs of an evolving digital network
values of or for intraoffice calls interoffice calls It specified end-to-end loss dB This loss was less than 200 mi and interoffice calls greater than 200 mi respectively
to be inserted in the receive path at the end office either by digital processing before
decoding or by analog padding after decoding
mi based The selection of fixed-loss value for interoffice calls greater than 200 was on
echo and noise considerations Some improvement in talker-echo performance could be offices expected due to the increased use of digital 4-wire equivalent trunks to the end control would be However on calls approaching 1850 mi where it was assumed echo VNL Plan lowers echo deployed any loss less than the value specified by the is less than in network and is performance Noise in an all-digital network an analog
constant for all connection lengths Assuming fixed loss of dB on these connections
the small decrease in overall echo performance is more than offset by the accompanying
increase in loss-noise GOS
The The Fixed-Loss Plan is compatible with network that is only partially digital
desired end office-to-end office loss value is achieved by allocating losses to analog
and switch are maintained at trunks Lossless digital facilities digital paths digital
at reference level This means that the equivalent power level of signal any digital
connection is the same as the of the original analog signal assuming point in power is tandem 0-level encoder If the final digital-to-analog decoding point at office
decode level should be used thus on connection to an analog TCT with loss of dB end the combined loss to the end office will be dB If the final decoding point is at the
office decode level provides the desired end office-to-end office loss of dB
discussed in Section NOTE Terms and concepts relating to digital transmission are
7.12.2
Plans 7.12.1.3 Metropolitan Area and Long-Distance
and the Fixed-Loss were to First the VNL Plan principles later plan principles applied networks These networks were the design of transmission plan for use in metropolitan end office-to-end office connections are less than 200 route designed so that all possible thus the need miles This ensures that round-trip delay rarely exceeds 10 ms obviating
7-43 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue 1994 Transmission April
Since successive calls can be trunked either directly for special echo-control measures
call to the next are minimized or via tandem offices differences in loss from one by
tandem trunks and near-zero losses on intertandem trunks specifying modest losses on
network network IntraLATA service is provided using metropolitan or long-distance that could to either of network or both Figure 7-14 shows an architecture apply type in networks and long- simultaneously Tandems are called sector tandems metropolitan tandem connects sector distance tandems in the long-distance network principal
tandems via intertandem trunks Tandems can be tandems or long-distance traffic as multifunctional acting as sector tandem for metropolitan long-distance for interLATA traffic tandem and even as an access tandem see Section 7.16.1
of trunks are used to intraLATA traffic As shown in Figure 7-14 three types carry
JOTs which connect any two end offices
TCTs which connect end offices to sector tandems or long-distance tandems
tandems tandems or either flTs which connect any two sector or long-distance tandem to tandem sector or long-distance principal
into sectors sector To implement metropolitan plan the area is divided geographic These are not necessarily comprises the serving areas of number of end offices areas take of the contiguous but the end offices offer blend of traffic to advantage
is served sector tandem that noncoincidence of busy-hour traffic loads Each sector by
end offices It also forms an intermediate switching point for traffic between commonly
provides end office switching functions
allows for loss of dB for an inter- The loss plan adopted for metropolitan networks of to dB was end office connection see Table 7-5 The facilities for which loss up of 1.5 dB to IT.ts unless allowed are no longer used loss objective applies analog tandem that meets one or both ends terminates in principal through-balance also as or access tandem requirements or in sector tandem that serves long-distance becomes 0.5 The loss from end office-to- In these cases the loss design objective dB
connection It will end office via one or more tandem offices is dB for an all-digital used fall between and dB when analog and combination facilities are
Table 7-5 Following are characteristics of the long-distance plan see
similar to those For an individual trunk shorter than 200 mi the loss objectives are
for metropolitan networks
used are designed for specific Analog trunks longer than 200 mi rarely now
loss plus VNL
All trunks other than JOTs of less than 200 mi have balance objectives
and traffic the Where trunk or trunk group is used for both metropolitan long-distance
more stringent long-distance requirements apply
7-44 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Transmission Issue April 1994
TCT
Legend
End Office
Principal Tandem
Sector and/or Long Distance Tandem
Figure 7-14 intraLATA Trunks
7-45 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue 1994 Transmission AprIl
Table 7-5 IntraLATA Trunk Losses ICL
Loss dB Trunk Network Notes
Objective Max
Interend Office lOT 3.0 5.0 Analog Metro LD200mi VNL6.0 8.9
3.0 Digital or Meiro
Combination LD 200 ml 6.0
Tandem Connecting TCT
Analog Metro 3.0 4.0 LD200mi VNL2.5 5.4
3.0 Digital or Metro
Combination LD 3.0
Intertandem ITF
Analog
STtoST Metro 1.5 STtoPT Metro 0.5
General LD VNL 1.4
Metro 0.0 Digital LD 0.0
Combination Metro 1.0
LD 1.0 45
Notes OrLD200mi
Maximum applies only when gain is supplied by negative-impedance
repeaters
0.0 to 3.0 dB permitted without gain 2.0 4.0 dB 200 0.0 to 4.0 dB permitted without gain Metro to LD ml
Balance required Facilities must be 4-wire ______
7-46 LEC Networks SR-TSV-002275 BOC Not. on the 1994 Transmission Issue April 1994
7.12.1.4 Loss Plan for Evolving Digital Networks
Introduction and Background
ANSI Standard Ti .508-1992 Network Peiformance Loss Plan for Evolving Digital rules for network loss Networks17 provides recommended design values and application that between for Public Switched Telephone Network PSTN connections are all-digital from end office-to-end office The standard also demarcation points or that are all-digital recommended loss values provides echo control and connection delay guidelines The intended to accommodate the evolution of planning rules and application guidelines are those Section while the PSTN to handle all-digital services such as of ISDN see 14 and SJNorth American maintaining compatibility with the current analog digital to transmission loss/level plans Additionally the standard provides guidelines promote networks with IC networks terminal the correct and easy interconnection of LEC which standards have been equipment and interconnecting networks for compatible be developed Standard T1.508 was developed with the intent that recommendations evolution of the implemented in manner that is consistent with the physical all-digital or network as opposed to retroactive application to existing facilities architectures services
and of bit integrity in The achievement of satisfactory echo performance preservation considerations in the of the standard all-digital connections were key development
the inherent The increase in round-trip transmission delay caused by processing delay multiplexers and of digital elements for example digital switches digital facility
that is manifested as talker echo DCSs is source of echo performance degradation See Section 7.4.4 for discussion of talker echo
As discussed in Section 7.6.3 digital signal processing such as digital-to-analog of unmodified conversion or the insertion of digital loss precludes the transmission
is so that bit streams across the network The maintenance of bit integrity necessary arrive at customers who use the network to transmit digital data can expect signal to To the the terminating demarcation point without modification accomplish this the standard recommends the insertion of network loss where required as near to from end- end-user terminal as possible goal when the connection is all-digital insertion the user terminal to end-user terminal is to migrate the control of loss to end-user terminal Until that time loss values that are dependent on the type of
of nearest the end-user connection are usually administered at the point switching
terminal Loss values that are not dependent on the type of connection can be conversion DLC remote inserted at the fmal digital-to-analog point for example
terminal or at the last point of switching
Network Loss Recommendations
the end-user terminals and the control of When the connection is all-digital including with the loss insertion has migrated to the tenninals the terminals should comply Standard EIATI1A-579-1991.18 This will ensure that each requirements of ANSI
7-47 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue 1994 Transmission AprIl
terminal will provide sufficient talker echo control to preclude the need for network- based echo control measures
the standard loss For digital connections terminated in analog access lines provides values that are dependent on the connection architecture
is For interLATA or interconnecting network connections the requirement dB
For intraLATA connections involving different LECs dB is the preferred value tandem office although dB may apply to connections not involving
For intraLATA connections involving the same LEC guidelines are
Oto6dB TypicallyOdB3dBor6dB
As indicated in the standard the choice of network loss value depends on performance considerations administrative simplicity and current network design
7.12.2 Loss Implementation
Loss implementation methods are dependent on the type of trunk
7.12.2.1 Trunk Types
7-15 as follows The various types of trunks shown in Figure are categorized
transmission facilities and interface with Digital thinks use only digital digitally
digital switching systems at each end
Combination trunks use only digital transmission facilities and interface digitally and interface at voice with with digital switching system at one end frequency any
type of switching system at the other end
in treated as trunks Trunks that use analog facilities wholly or part are analog the of interface Trunks that use only regardless of the switching systems and manner voice at both ends are treated as analog digital facilities but interface at frequency
regardless of the switching systems
interface with Trunks that use both analog and digital facilities and digitally digital
end and interface at voice with of switching system at one frequency any type Terminated switching system at the other end are called Digitally Analog DTA
trunks and are treated as analog trunks
7-48 BOC Notes on the LEC Networks 1994 SR.TSV-002275 TransmissIon Issue AprIl 1994
Digital Trunk DJ
Combination Trunk VF ______AorD
Analog Trunks
AorD AorD
VF VF
Terminated Digitally Analog Trunk DTA VF EIIIID
Legend Analog
Digital VF Voice Frequency
Switch
Figure 7-15 Trunk Types
7-49 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Transmission
Definitions 7.12.2.2 Signal Level Conventions and Analog
Transmission Level Points Transmission Level Points TLPs are points in circuit where TLP values are assigned The TLP value is the ratio expressed in dB of signal of the same at reference point called zero power at that point to the power signal is is Transmission Level Point TLP point where the TLP value generally referred to as an Transmission Level Point TLP
of transmission TLPs are TLPs are defined for individual trunks in each direction are normally defined only at points where voice-frequency analog signals expected
levels to common reference the UP concept enables By referring all signal point and maintained In addition losses in analog circuits to be conveniently provisioned desired TLPs facilitate the evaluation of interference signals in relation to the signal
the of the The initial UP of trunk in the transmitting direction is equal to UP value of and switching office Historically end offices have been assigned UP standard values have been analog tandem offices TLP value of In addition UP
test of and carrier assigned to input and output points repeaters Systems
of TLPs in tandem trunk utilizing an Figure 7-16 illustrates the application connecting the of the analog carrier system In the transmitting direction the trunk assumes UP standard end office loss of 16 dB represented by pad is required to interface the 10 dB loss lowers the from at the carrier 16 UP at the carrier system input UP of trunk The difference between initial and fmal system output to at the far end the final differs from UPs indicates the loss of the trunk As is generally the case the UP
the UP of the office at the receiving end
in the direction to end office is similar The analysis of the TLPs opposite tandem indicate the loss of the trunk Again the initial and final UPs and respectively TLPs of the carrier Different pad loss values are required to interface the input/output
direction of transmission system in this
switch connection Considerable TLPs are not defined at interim points in digital or switches when confusion has arisen from attempts to assign UP values to digital they
at where voice- are used as tandems As noted previously TLPs are defined only points must be encoded frequency analog signals are expected Any analog signal digitally and/or transmission takes decoding of the before digital switching place Similarly in order to obtain an New concepts digital signal must take place analog signal connections discussed later are required to analyze digital
level is the level Reference Level At any point in an analog circuit reference power Thus in dBm that is numerically equal to the TLP value at that point signal having
value is said to be at reference level and is normally power level equal to the UP have level of dBm at referred to as dBmO signal since it would power 10 to 30 dB below reference level UP Voice and voiceband data signals are normally
7-50 LEC Networks SR-TSV-002275 BOC Notes on the 1994 Transmission Issue AprIl 1994
Trunk TLPs
Trunk TLPs
ICL dB
losses Note Pad values shown include hybrid and other transmisson path
Transmission Level Points FIgure 7-16 Analog Trunk
Loss of trunk is the inserted Connection Loss The Inserted Connection ICL of the 1004-Hz transducer loss of the circuit referenced to the nominal impedances The ICL reflects all of the gains and/or offices 600 or 900 that it interconnects switch the circuit to losses from the outgoing appearance at the originating through
termination at the outgoing side of the terminating office
well for analog carrier or digital- The defmition of ICL applies equally voice-frequency mentioned above are at voice carrier trunk facilities provided that the appearances
if either both switches are digital these voice-frequency frequency However or traditional manner exist In these ICL cannot be defmed in the appearances do not cases and level measurements can be performed only at analog test points
that reduce the standard milliwatt Test Pads Test pads are fixed-value attenuators be circuit TLP value at the where the test signal is to dBm test signal to the point with dB test pads TP2 End applied Analog tandem offices were normally equipped not associated with digital offices do not have test pads TPO Test pads are generally switches
Loss of trunk is the Expected Measured Loss The Expected Measured EML test conditions This loss is 1004-Hz loss that is expected to be measured under specified and losses of the trunk in the specified measuring calculated by summing all gains for with actual measurements configuration It is used as reference comparison
7-51 BOC Notes on the LEC Networks 1994 SR-TSV-002275 TransmIssion Issue AprIl 1994
The EML includes test access losses for the connection of both automatic and manually the operated measuring equipment If test access loss is negligible EML is essentially differ same as ICL Losses caused by test pads and office wiring can cause EML to
significantly from ICL
Actual Measured Loss The 1004-Hz loss of trunk that is actually measured with
is called the trunk in its specified state using the specified measuring configuration Actual Measured Loss AML AML is compared with EML to determine loss performance
7.12.2.3 Loss Implementation for Analog Trunks
Figure 7-17 shows an analog tandem office TP2 connected to an analog end office via the digital carrier facility The type of facility is not important for this analysis however
trunk is classed as an analog trunk AtrunkwithanlCLof3 dB is illustrated Ignoring of the tandem switch and any wiring or trunk circuit losses the loss between the center The level received at both the end office line appearance is dB as indicated test of offices is dBm because of the 2-dB test pads at the tandem office Thus the EML this trunk is5 dB
Aeieren DRS Digital Signal
Note Pad values shown kdude hybrid and other ansmtsslon path bases
Figure 7-17 Analog End Office to Analog Tandem
7-52 SR-TSV-002275 BOC Notes on the LEC Networks 1994 TransmIssion issue AprIl 1994
7.12.2.4 Signal Level Conventions and Definitions Digital
Digital Milliwatt An important concept relating to signals in digital facilities is Digital
is of 0-dBm 1000-Hz Milliwatt DMW DMW digital representation analog words has been the sine wave representation consisting of eight 8-bit adopted by
the for that is encoded to the 255 1TU-T formerly CCITT DMW according j.t encoding law
The DMW is not recommended for transmission over DS facilities because the bit
the of channel banks Under certain pattern duplicates framing sequence D-type conditions the bank can frame on the DMW sequence causing frame misalignment condition the be used without any accompanying alarm However DMW can internally the rate in digital switching systems because these systems do not operate at DS
of In addition it is not advisable to inject 1000 Hz signal into DS1 system because the harmonic relation to the 8000 Hz sampling rate Interference signals can result in erroneous loss measurements when these frequencies are mixed
is encoded Digital Reference Signal The Digital Reference Signal DRS an analog
international is sine wave in the signal which by current convention frequency range of 1013 Hz to 1022 Hz having power of dBm 0.03 dB ITU-T formerly the CCITT and ANSI are considering adoption of specific encoded signal which uses
797-byte repetitive pattern and has frequency of approximately 1013.801756- Hz
The avoidance of the DMW sequence means that these DRSs do not have the limitations of the DMW and can be transmitted over the network For reference level purposes DRS is equivalent to the analog milliwatt signal in analog facilities
insert loss before is in Digital Pads Digital pads are used to decoding When signal
be to the bit stream without first digital PCM form gain or loss can applied directly from code set converting it to analog simple look-up table can be used to convert one to the other or the nonlinear PCM can be converted to linear code multiplied by the gain or loss desired and converted back to nonlinear PCM This avoids the cost of digital-to-
avoid since analog-to-digital conversion but does not signal impairment approximately the same amount of quantizing noise is added in either case
noise ratio because of Digital level control always reduces the signal-to-quantizing round-off errors in mapping between code sets This differs from analog gain
adjustment which seldom affects signal-to-noise ratio
noise over from To provide nearly constant ratio of signal-to-quantizing signal range 40 to dBmO non-linear 255 PCM coding is used This range closely tandems and approximates the range of talker levels to be found at end offices and
all talkers loss or assures optimum quality for almost Digital gain pushes speech power inserted It toward one end or the other of this range by the amount of the loss or gain the reduces the code set used since the maximum output signal will be dB below
maximum code for dB loss or the minimumwill be dB above the minimum code for dB gain
7.53 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue AprIl 1994 Transmission
transmission Encoders Encoders convert analog signals into digital signals for
trunks and switches If sinusoidal of dBm through digital facilities such as signal the encoder the encoder is said to have an at an encoder input results in DRS at output The side of the encoder is encode level of and is called an e-level encoder input said to be an Encode Level Point ELP
is For 255 encoders overload clipping begins to occur at an input power level that
that would DRS at the 3.17 dB higher than the power level of sinusoid produce level of e-level encoder is 3.17 dBm encoder output Thus the overload an
into If DRS at decoder Decoders Decoders convert digital signals analog signals
of at the decoder the decoder is said input results in sinusoidal signal dBm output side of the to have decode level of and is called d-level decoder The output decoder is said to be Decode Level Point DLP
denote the Equivalent Power Level Equivalent Power Level is term used to power encoded into bit stream level of an analog signal that is digital Equivalent power The should not be confused with the actual power of the digital signal equivalent power the of 0-level can be measured indirectly by mapping the digital signal to output be measured with decoder The power of the decoded signal can of course directly sometimes referred to as analog measuring equipment The equivalent power is power relative to 0-level decoder
7.12.2.5 Loss Implementation for Combination Trunks
connected to an end office via digital Figure 7-18 shows digital tandem office analog the the carrier carrier facility Because the interface is digital at digital switch digital discussed earlier in this Section Using the facility is considered combination trunk as of the loss of dB is indicated concept of equivalent power at the center digital switch indicated in the from the tandem to the end office line appearance and dB loss is be to this trunk opposite direction It is apparent that an ICL cannot assigned the However with the tandem office encode and decode levels of and respectively
of this trunk is dB in both test level received at both offices is dBm thus the EML
directions
Trunks 7.12.2.6 Loss Implementation for Digital
connected to end office via digital carrier Figure 7-19 shows digital tandem digital this connection is digital trunk Using the facility As discussed earlier in this Section the two it be seen that there is no loss between concept of equivalent power can trunk Both switches encode at and switches ICL has no meaning with respect to this
is the tandem to the end office line appearance decode at Thus the loss dB from
of the trunk is dB in both directions and dB in the opposite direction The EML
7-54 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Transmission Issue AprIl 1994
Digital Tandem Office Analog End Office
i46dBLoss Digital OdBLos4 Interface
-8.5 TLPIp DRS 8.5 p1
2-Wue Digital Analog Sh Caer Swit Fac$ty TLP DRS
OEL -6DLI
EML6dB -l
Test Test -6 Tone Tone OdBm -6dBm
Test ri Equipment
Note Pad vaiues shown Indude hybrid and other transmission path losses
Tandem Figure 7-18 Analog End Office to Digital
End Office Digital Tandem Office Digital
Digital l6dBLoss Dig Interface 0dB Loss Interlace
DRS I-i
Dig Digital Digital .1 OEL Sh Carrier Sh Facility Une DRS 14
-6DLI OEL -6DJ EL 6DLP Tone 6DLP ROM EML6dB
Test Test dBm -6 dBm Tone Tone
Test
Equipment Equipment
Office to Tandem Figure 7-19 Digital End Digital
7-55 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue 1994 Transmission AprIl
As mentioned previously the Fixed-Loss Plan and the Loss Plan for Evolving Digital be external to Under the Networks both provide for loss insertion to digital path end office The Loss Fixed-Loss Plan the loss is inserted in the receive channel at each for loss insertion in the receive Plan for Evolving Digital Networks makes provision conversion channel at each end office or at the digital-to-analog point Thus with 0- connection from end office-to-end office with analog loops at each end begins
level level encoder and ends with 6-level decoder The equivalent signal undergoes no change between the encoder output and the decoder input
7.13 Operator Services Transmission
in located These Operator services are provided by personnel centrally position groups assistance and services include iniraLATA long-distance assistance directory intercept mobile communications on the type of traffic being special services such as Depending on tandem switches digital Automatic Call Distributors served the position groups home centers are often located ACDs or Automatic Intercept Systems AISs Operator connected to hundreds of miles from the customers being served and are normally
switching centers by digital facilities
7.13.1 TransmIssion Objectives
of an The general transmission objective for the customer-to-customer portion operator- the same as for an unassisted assisted call is loss-noise-echo GOS that is essentially for the call over the same distance see Section 7.11 The transmission performance to that on connection between the operator and the calling customer should be equivalent and the called the short direct-dial connection Between the operator customer the final customer-to-customer connection performance should be equivalent to that on
is to voice level for all participants of The intent of these objectives ensure nearly equal
conference call
factors such as noise in the room Operators are influenced by environmental operating acoustic ratio is 29 dB For over-the-ear headsets The objective for the signal-to-noise Pressure Level this translates into room-noise requirement of 55 dBA average Sound and 62 dBA at the position The using an weighting network peak operator headsets 52 and 59 CIBA respectively The corresponding values for in-the-ear are level of 20 Attention to placement quoted noise levels are referenced to micropascals to meet these of adjacent consoles and sound treatment of the room are required
objectives
Service 7.13.2 Directory Assistance and intercept
and services known collectively as Many LECs provide directory assistance intercept The ACD network number services using ACDs to forward calls to operator groups network For example local directory is basically similar to the regular message
7-66 SR-TSV-002275 BOC Notes on the LEC Networks 1994 TransmissIon Issue AprIl 1994
functions tandem office assistance or intercept service is configured so that the ACD as discussed in Section 7.16.1.4 As Directory assistance service for interLATA traffic is
often located at considerable distance with other operator services the personnel are from the customer being served
for number services is to on local service that The transmission objective provide quality and on service is equivalent to that of short long-distance call long-distance quality level from that is equivalent to normal call between the same areas The volume an
automated voice-response unit should be comparable to that of live operator Digital lossless For an ACD network the ICL ACDs with digital trunking are typically analog end office the call and the ACD switch objective is dB between the originating Concentrators or tandem offices may occur in the routing with an additional 0.8 dB
allowed for the concentrator trunk The loss-design objectives for analog number
services are summarized in Table 7-6
Table 7-6 Loss Objectives Operator Services
Equivalent Nominal Trunk Type Trunk ICL dB
Local DA Tandem
End Office-ACD Connecting 3.0
ACD End Office- Tandem
Concentrator Connecting 3.0
Tandem-ACD Intertandem
Concentrator-ACD lntertandem 0.8
End Office-ACD AIS 3.0
AIS and ACD End Office- AIS 3.0
Intercept Concentrator
Concentrator- Intertandem 0.8
ACD or AIS
Trunk Concentrator Unless gain transfer is used No only
service is the recorded voice-answer feature of the mechanized intercept provided by
MS shown in Figure 7-20
Automatic Center Routine announcements are provided at the remote Intercept AIC
further information can then be connected to an at the home customer requiring operator AIC
7-57 SR-TSV002275 BOC Notes on the LEC Networks 1994 Transmission issue AprIl 1994
Operator Position
Legend
EO End Office
Trunks Figure 7-20 Typical Automatic Intercept System
The MS transmission plan is similar to the intercept portion of the ACD plan The MS
switches should meet long-distance tandem office transmission requirements
7.13.3 IntraLATA Long-Distance and Assistance Service
to services can be found in Proposed generic requirements relating operator equipment FR-NWT-000271 OSSGR Operator Services Systems Generic Requirements.19
is shown in 7-21 The end The system plan for operator services Figure calling party connected to the bridge office and called party end office are operator through
is needed via the voice-data links These links are used only while the operator When
is and the tandems are connected the operator functions are complete the bridge dropped tandems would be via an intertandem trunk If this were an interLATA call the the connected via the tandem interLATA connecting trunks by an IC upon release of
for related to interLATA calling operator see Section 7.16.1.4 terms
7.13.4 Operator Services Transmission Plan
services transmission is shown in Figure 7-22 The ELP The basic digital operator plan in the Fixed-Loss In an all-digital and DLP shown at the end office are the same as Plan the end office and switched the end environment the analog signal is encoded at by The office and tandem offices without additional signal processing required
7-58 Networks 1994 SR-TSV-002275 BOC Notss on the LEC Transmission issue April 1994
Operator Position
Groups Access Tandem for Stand-Alone Host
LATA Tandems
End Office
Connecting Trunto
Closedown Dedicated
Voice end Data Unics for Operator Functions
End Office
Standalone or Combined with Access Tandem
Figure 7-21 Operator Services System Plan
Receive
.8 TLP
Access -6 DLP Tandem Operator Headset
OELP
UP Transmit Operator
Sc.tsysteni
Services Figure 7.22 Basic Digital Transmission Plan Operator
7-59 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue 1994 Transmission April
in the transmission loss is inserted by an analog pad after decoding operator subsystem and to the end office The operators voice signal is encoded in the subsystem transported also without further processing Loss is inserted in the end office receive path by digital after padding before decoding or by analog loss decoding
To meet transmission objectives the operator-speech signal or synthesized speech from
should at the host for example an Automated Coin Toll Service system appear that from switch at level nearly equal to the average level of speech arriving at point local customers that is equivalent to 1004-Hz tone of 21 dBm
in the are based on the use The headset-jack TLPs that are derived following paragraphs W1-0003 Generic of headsets conforming to specifications in TA-N 14 Requirements for should allow Telephone Headsets at Operator Consoles.20 Operator services equipment with headsets for an adjustment of these TLPs by dB so that objectives can be met receive efficiencies exhibiting different transmit and/or
SPL to 20 Assuming an average speech input of 88 dB relative micropascals transmit To conforming headsets should produce 17 dBm power level at the jack For meet the 21 dBmO objective the TLP at the transmit jack is specified as headsets having 10 dB lower TOLR TLP of may be used instead
level as The objective for the receive channel is to deliver as high voice-signal possible without exceeding Occupational Safety and Health Administration OSHA acoustic of limits for work environments For conforming headsets an incoming signal 29 dBm will be converted to the desired level of 87 dB SPL To meet the 21 dBmO objective the receive jack UP is set at
distance from As stated previously operator systems may be located at considerable customers Connections may consist of large amounts of fiber facilities that have and transmission become relatively low propagation velocity delay may significant of echo Network layouts involving more than or ma echo-path delay require loss-noise-echo as cancellation or voice-switched attenuators to assure good GOS perceived by the operator
7.14 Transmission Limits IntraLATA Networks
are set To ensure that networks provide satisfactory performance objectives requirements for trunks loops and switching offices Trunk loss C-message noise impulse noise end office noise are balance limits loop-noise objectives/requirements and requirements discussed here
for test limits refers For some parameters two categories are used assigning Digital channel banks with cable extensions of one mile to facilities using D2-equivalent or later cable of mile or less All other facilities are or less This category also applies to one
considered to be in the analog category
in terms The requirements for most intraLATA trunk transmission parameters are given limits of Pre-Service Limits PSLs Immediate Action Limits IALs and maintenance
7-60 SR-TSV-002275 BOC Notes on the LEC Networks 1994 TransmissIon Issue AprIl 1994
that is allowed to of PSLs represent maximum or range of parameter prior turn-up
in-service circuit is service IALs are thresholds beyond which performance of an Maintenance limits deemed unsatisfactory and immediate corrective action is necessary trunks that for lie between PSLs and LALs and are used to flag should be scheduled corrective action
7.14.1 Trunk Loss Limits
deviation of the from the EML of to 0.5 dB is For pre-service measurements AML up trunks allowed The LAL is 2.0 dB for digital trunks and 2.5 dB for analog As stated Individual exchange carriers may use more stringent values for LALs above limits maintenance limits lie between the PSLs and IALs The specific maintenance are determined by each exchange carrier
7.14.1.1 TestTones
be Tones for Test tones used for short-term tests are currently allowed to at dBmO long-term tests operate at 10 dBmO
7.14.2 C-Message Noise Limits
7-7 the Noise must be kept within defmed limits to provide good service Table gives limits in terms of C-message-noise PSLs and IALs for message trunks These are given should be subtracted dBrnCO which means that the TLP at the point of measurement trunks from the measured noise level to obtain corrected result The limits for analog cable are mileage dependent The digital category includes trunks on voice-frequency individual carriers use more with lengths of 15 mi or less Again exchange may limits determined the individual exchange carriers stringent IALs Maintenance are by
and lie between PSLs and IALs
7.14.3 Impulse Noise Requirements
data facsimile Impulse noise is important on channels used for voiceband or noise results transmission Where digital facilities are involved high impulse usually
affects all 24 circuits in the from high error ratio on DS system which digroup bit will be Where Bipolar with 8-Zero Substitution B8ZS coding is involved errors
and other terminals if are introduced by high-capacity digital multiplexers they optioned The same can occur if equipment on for ordinary bipolar operation Section 7.6.4 for B8ZS bipolar facility is unintentionally optioned
7-61 SR-TSV-002275 BOC Notes on the LEC Networks 1994 1994 Trenemlesion Issue April
Table 7-7 C-Message Noise Limits
Limit Values dBrnCO
Limit Facility Facility Length mi Type Type 0-50 51-100 101-200 201-400 401-1000
38 Pre-service Analog 29 31 33 36 26 26 26 26 Digital 26 43 Immediate Analog 34 36 38 41 30 30 30 30 Action Digital 30
limits if the For voice-frequency cable facilities or for cable extensions of digital facilities the digital are applicable
than 15 add dB to tlar limit cable length is 15 rm or less lithe cable is longer mi digital
time Because impulse noise occurs sporadically measurement requires relatively long 15-minute Time periods Measurement of single channel normally requires period facilities can be saved in the evaluation of complete trunk groups that share common by of minutes is using sampling techniques and shorter measurement period Sampling noise feasible because trunks in common route are assumed to share similar impulse
exposure
Table 7-8 The Impulse noise limits for trunks facilities and connections are given in should requirement on trunk group is that no more than 50 percent of measurements
noise level in excess of value The measurement is display an impulse specified threshold the level and noting performed by adjusting the impulse counter to specified whether the count at the end of minutes is or less acceptable or or more unacceptable
7.14.4 Balance Limits
conversions at Through-balance procedures are necessary to control echo at 4- to 2-wire intraLATA network any 2-wire tandem switch in the long-distance Through-balance in Table 7-1 The office terminal-balance limits at 2-wire switching point are shown office in Sections 7.4.4 and 7.12.1 limits apply at long-distance tandem as explained
limits in TCTs in the long-distance intraLATA network should meet the terminal-balance
all of TCT connected to tandem Table 7-1 Digital switch applies to types digital the Fixed-Loss and the Loss Plan for switch This higher return loss is needed because for control of talker echo The analog limits Evolving Digital Networks use reduced loss
apply to all other TCTs
have at least To meet echo-control objectives long-distance tandem office should the PSLs and none below the IALs for 50 percent of all trunks meeting or exceeding for service below the ERL or SRL For initial installation no trunk should be turned-up
7-62 SR-TSV-002275 BOC Notes on the LEC Networks 1994 TransmIssion Issue AprIl 1994
Table 7-8 Impulse Noise Limits
Measurement Limits Level
dB below Connections 15 counts in 15 mm on at least 85% signal
of calls
all 59 dBrnC Loops 15 counts in 15 mm on loops
50% of calls Crossbar 54 dBrnC Switching Offices counts in mm on test
Step-by-step 59 dBrnC
IAL 20 counts or more in mm Electronic or 47 dBrnC
digital
Voice 54 dBrnCO Trunks counts in mm on 50% of trunks freq
in group Compandored 66 dBmC0
or mixed
IAL 20 counts in mm Digital 62 dBrnC0t Non
compandored 0-125mi 58dBrnCO
126-l000mi 59dBrnCO
Facilities counts in mm on 50% of channels Voice freq 52 dBrnCO
Compandored 64 dBrnCO
or mixed
IAL 20 counts in mm Digital 62 dBrnC0t Non
compandored 0-125mi 56dBrnCO
126-1000 mi 57 dBrnCO
Office or referred toCO through 1004-Hz loss Level at Central CO
With 13 dBmO holding tone
is the level is 67 dBrnCO Holding tone not required if holding tone used
763 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 Transmission
below the IAL should be PSL limit On subsequent testing any trunk measuring removed from service and repaired
offices to determine whether Two-wire long-distance tandem are surveyed periodically These can be done using the office continues to meet echo-control objectives surveys
and SRL measurements are made on small sampling technique in which ERL would be circuits in Results of such sample percentage of each trunk group survey half the measurements to or expected to have distribution with at least equal greater than PSLs and none less than IALs
basis more reliable data than Periodically testing trunk groups on routine can produce the small-sample survey technique
on The return-loss values obtained for terminal balance are highly dependent proper
this includes the use of in design and installation of the TCTs On 2-wire paths pads loaded metallic trunks short metallic trunks and impedance compensators in
7.14.5 Loop Noise
subscriber at customer Table 7-9 lists the objective for noise measured on loops action for that limit demarcation points and indicates recommended loops exceeding Table 7-8 Impulse noise limits for loops are given in
is to As DLC and RSU technologies are introduced loop noise performance subject to noise induced by change Long metallic loops with their significant exposure power electronic circuits can be lines become relatively uncommon However modem
induced longitudinal currents The susceptible to saturation due to low-frequency for noise The noise at the demarcation point resulting harmonics can be source of
is combination loops served via Universal Digital Loop Carrier UDLC Section 7.15 of noise of the noise at the central office terminal and the approximately 18 dBrnCO
result is that cases of high contributed by the remote terminal decoder The relatively noise levels rise noise approaching the 30-dBrnC limit become less common although
on average
Table 7-9 Loop Noise Objectives and Requirements
NMS5 Reading Action Significance dBrnC Recommended
20 Objective for all loops None
noise Further analysis and 21 to 30 Loop marginal
as 30 dBrnC approached investigation
Immediate investigation 30 Unacceptable
Noise Measuring Set
7.64 the LEC Networks 1994 SR-IS V-002275 BOC Notes on Transmission issue AprIl 1994
and RSUs the remote For loops served via Integrated Digital Loop Carrier IDLC and demarcation noise levels are terminal decoder becomes the only source of noise point somewhat lower than for loops served by UDLC
7.14.6 Central Office Noise
discussed in this of noise that affect transmission through central office are The types section
7.14.6.1 Cross-Office Noise
cross-office noise This includes the Noise generated in the serving end office is largely line net sum of all noise sources on connection between any two appearances and corrosion or wear of switching Excessive battery noise marginal codec chips of cross-office noise for per-line codecs in equipment are some of the sources Except
is such that excessive noise occurs on random digital offices the nature of noise sources random occurrences become too connections rather than on all connections If these terminal will become frequent the noise performance at the average end-user end office must be within defined unsatisfactory Therefore noise in the serving kept
limits
noise and The cross-office noise test consists of measurements of steady-state average-
of the or the regular location of peak noise The reading of the position digital display noise measurement The the meter needle of noise-measuring set is the steady-state the set and average-peak measurements are made by observing noise-measuring the measurement the far end of averaging the peak readings over few minutes During the connection should be properly terminated
selected cross- The condition of the office is judged by measurements of 20 randomly of the measurements of office connections An office is considered satisfactory if none limits shown in Table 7-10 either type exceeds the applicable lower
Table 7-10 End Office Noise Requirements
Average Peak
Office Steady-State Noise dBrnC Type Noise dBrnC Meter Damped
Lower Upper Lower Upper Limit Limit Limit Limit
22 26 30 Analog 18
25 29 33 Digital 21
7-65 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Transmission Issue April 1994
An office is considered unsatisfactory if four or more steady-state or average-peak measurements exceed the lower limits or if any single measurement of either type exceeds the upper limits In this case corrective action should be taken
If one two or three measurements of both types exceed the lower but not the upper limits the condition of the office is considered doubtful In such cases another 20 connections are tested to improve the sample accuracy if no more than of the 40 readings exceed the lower limits the office is now acceptable On the other hand 114 or more of the 40 measurements exceed the lower limits the office is unacceptable and needs corrective action
and classified of host electronic An RSU is switching entity controlled by as part
switching system In many respects such remote is analogous to peripheral frame served it within the host switch The RSU should be transparent to subscriber by
Hence the GOS for the RSU-served customer should be equivalent to that of user
served by the host From noise-impairment point of view loops from the subscriber to combination of the the remote should satisfy the usual loop requirements The remote the connecting channel and the host switching system is considered as single unit even the the though the link channel is normal carrier facility To maintain necessary GOS noise level of the channel must be kept below 20 dBrnC
7.14.6.2 Impulse Noise
the time-slot In digital switches impulse noise can come from defective circuit packs in
interchange which cause bit errors Impulse noise limits for switching offices are given
in Table 7-8
7.15 Loop Transmission Design and Characterization
end office is The loop between the demarcation point at the customer location and the an
important link in any telephone connection Satisfactory design of the loop is as
important to overall transmission performance as the design of trunk or switch Loss
loss is controlled the use of objectives for loops are not explicitly stated instead loop by
design rules
Before 1980 almost all loops were designed according to resistance design 96 percent made third or long-route design percent The success of DLC possible design plan the carrier serving area concept Fundamental to all three plans is the notion that and designing loop facilities on an individual basis would be prohibitively expensive basis extremely difficult to administer Instead loops are laid out on global through rules designed to help ensure the following
No loop exceeds the office signaling range
7-66 BOC Notes on the LEC Networks 1994 SR-TSV-002275 TransmissIon Issue Apr11 1994
assumed station All customers receive at least 20 mA of loop current into an
resistance of 430
The distribution of loop transmission losses is satisfactory
7.15.1 Revised Resistance Design
urban/suburban Revised Resistance Design RRD is the current design plan replacing of 1500 or less and resistance design RRD rules apply to loops with resistance length
that is economical of 24 kft or less RRD is an outside-plant design consistent and most capable of providing improved loop operationally simple importantly
transmission performance
and resistance are that RRD allows The major differences between this plan design loaded instead of 1300 central higher maximum loop resistance for loops 1500 the amount of allowed The maximum office range permitting and reduces bridged-tap that in the for nonloaded is the same in both plans except RRD length of 18 kft loops of The rule changes result in maximum length includes the length any bridged-tap Under some circumstances the transmission improvements and outside-plant savings of the increase in maximum loaded-loop RRD plan reduces dc signaling margins because switches have below 1600 resistance to 1500 fl However few modern loop ranges
Table 7-11 summarizes the RRD plan rules
7.15.2 Modified Long-Route Design
first found in rural are designed using DLC as Loops longer than 24 kft typically areas also summarized in Table 7- choice or Modified Long-Route Design MLRD MLRD basis 11 was introduced in 1980 to provide for loops range-extended on per-line as Resistance Zone 18 18 Under this plan the 1500- to 20004 range is designated RZ 2000- to 28004 28 requires dB with additional gain dB required The range RZ
of gain
extenders which automatically When wire center is totally equipped with newer range maintain from to as it is not necessary to switch their net-gain settings dB required transmission zones in that wire center Therefore all loops under and administer separate zone However some MLRD can be considered to be in single range-extended of limitations by zone or have large number companies that administer ringing range
still RZ 18 and RZ 28 older range-extension circuits may use zoning
rural and can be applied anywhere it is economically MLRD is not limited to long loops While need not be rebuilt to conform to the new plan the gain justified existing loops that utilize cable indicated here are used for new loop designs existing application rules
7.67 BOC Notes on the LEC Networks 1994 SR-TSV.002275 Transmission Issue AprIl 1994
Table 7-Il Loop Design Plans
Modified Design Carrier Serving Revised ReaLs- Long-
Parameter Area tenet Design Route Design
kft 1300 1501-2800 Loop Resistance N/A limited by loss 0-18 max
lS-24kft lSOOmax
Full H88 Loading None Full H88 18 kft
Cable Gauging Two gauges except
stubs and fuse cables
max lengths including Two-gauge BT combinations 22- 24- 26-gauge .24- 22- and/or 19- preferred gauge l2kft .26-gauge 9kftt
Nonloaded cable ES Bridged Tap El Total BT 2.5 kft BT
and End Section max BT 18 kIt max to 12 kft
ES NosingleBT2kft TotalBT 6kftmax
Loaded ES BT to 12 kIt
Transmission None supports Compatible with No digital services
Limitations ISDN DSL 56-kb ISDN DSL No Needs range extender
services with if data and despec- digital gain
kft 1500 ialized special services 18
Includes only the resistances of the cable and loading coils
Area in scene rural areas At least one exchange carrier uses an extended Carrier Serving CSA
This variant allows loading but does not accommodate digital services
Multigauge designs incorporating 26 gauge are restricted in total length to 12- Bli kft
where is the total of the and BT is the sum of bridged taps of all gauges L26 length 26-gauge
7.15.3 Concentrated Range Extender with Gain
Gain Some analog electronic wire centers use Concentrated Range Extender with in outside CREG design This plan allows increased use of fine-gauge facilities the with of concentration plant by providing repeaters each associated stage switching the RRD and The CREG design is compatible with the loading arrangements in both
MLRD plans
7-68 BOC Notes on the L.EC Networks 1994 SR-TSV-002275 TransmIssion Issue AprIl 1994
7.15.4 Performance of RRD and MLRD Loops
similar schemes have the same end-section The RRD and MLRD plans employ loading with combination of cable gauges These and bridged-tap rules and are compatible any transmission pei-formance over older plans and give approximately plans offer improved and ROLR see Section 7.4.1 the same minimum loop ratings that is TOLR
of TOLR and ROLR for maximum-loss RRD loops as function Figure 7-23 shows the in the worst case with maximum cable resistance loop length The figure applies for Dashed lines show the design limit objectives TOLR bridged-tap and end section the resistance plan in and ROLR The RRD plan results in improved ratings over design loss and comes closer to meeting the the 12- to 18-kft region where maximum occurs on this Performance offered by the long-route design design limit objectives in zone where the MLRD differs in the 1500- to 600-a resistance range MLRD plans primarily in better performance plan provides gain resulting
7.15.5 The Carrier Serving Area Concept
services via loop facilities led The evolution to network that can readily provide digital be served CSA is an area that is or by to the Carrier Serving Area CS concept may into the end office switch DLC DLC may be either stand-alone UDLC or integrated are of providing on IDLC All loops within CSA are nonloaded They capable service data service up to nondesigned-basis conventional voice-grade message digital Lines for ISDN and most locally switched 2-wire 64 kbps Digital Subscriber DSLs services channels pair-gain pairs on the DLC system voice-grade special Ordinary attenuation in the cable within the have loss of dB or less thus allowing for physical limited attenuation not by dc resistance Bridged- CSA Loop length in the CSA is by CSA controlled to capability for high-speed digital operation tap lengths are preserve
design is now used for most loop growth
7-11 The table indicates that within the The CSA design plan is summarized in Table cable is dependent on the CSA the maximum allowable loop length involving 26-gauge 7-24 This is illustrated in Figure length of bridged-tap dependency
7.15.6 Digital Subscriber Line
transmits 160 in both directions The DSL for ISDN Basic Rate Access BRA kbps The DSL is intended to operate with cable simultaneously on nonloaded cable pair between DSLs in the same cable at kHz To minimize crosstalk loss of up to 42 dB 40 that is two recoded into Quaternary 2B1Q form binder group the signal is Binary on the line see Section 12 Almost all loops binary pulses become one quaternary pulse whether RRD or its predecessors will transmit designed to resistance design criteria device 18 kft The customer provides Network Termination NT DSL signal out to in the to into the DSL transceiver the customer side of the demarcation point operate on DLC channel units DSL can be extended out to CSA on central office With suitable
facilities
7-69 SR-TSV-002275 BOC Notes on the LEC NetworksI 994 Issue April 1994 Transmission
-49 45
-47 47
-45 49
-43 51 -0
-J
I-
53 -41
-39
-37
10 20
Loop Length kft
Figure 7-23 Objective Loudness Ratings RRD
7-70 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Transmission Issue April 1994
12
11
Longest CSA Loop 10 kft
Length of 26-GA Cable in kft
Legend
BT Bridged Tap GSA Carrier Serving Area GA Gauge
of CSA Figure 7-24 Maximum Length Loops
7-71 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue 1994 Transmission April
and Bit-Rate Other emerging loop technologies are Fiber in the Loop FITL High These discussed in Section 12 Digital Subscriber Line HDSL are
7.15.7 Spectrum Management In Loop Plant
Loops are used for transmission of wide variety of signals other than voice
Voiceband data
Analog program material
Local Area Data-Channel LADC traffic
Public Switched Digital Service PSDS 56-kbps signals
Data-above-voice operation
ISDN BRA and Primary Rate Access PRA signals
DS high-capacity services
Digital data services of 2.4- through 64-kbps speeds
with Loops for most of these services coordinate satisfactorily with one another data voiceband circuits and with the Ti carrier spans used in loop plant however
interference with 15-kHz circuits signals may cause excessive program Single-channel to data When interference analog loop-carrier systems are uniquely exposed 56-kbps coordination The level of the occurs it becomes special problem disturbing signal may have to be reduced coupling losses increased or amplitude raised on the disturbed substitute DLC circuit It may be necessary to reassign service to different cable pairs or
facilities
exist for data-above-voice The use of wide variety of proprietary formats systems effects of ISDN-to 2B 1Q line-code standard for ISDN BRA is intended to control the ISDN near-end crosstalk which would be more severe if code with greater high- least two frequency content were used however ISDN BRA currently also involves at in the binder these can reduce prestandard line formats If present same group signals tables that each others error margins Studies have resulted in spectrum-management coordination of these indicate maximum loop ranges to ensure of combinations systems maximum avoids Thus for technologies in use today observance of these ranges crosstalk problems
7.15.8 Loop Surveys
the characteristics of subscriber The latest Studies have been made to quantify loops which the 1-kllz 9OO- one taken by the BOCs in 1983 provided data from median in the end office to the insertion loss from the Main Distributing Frame MDF This value did not differ demarcation points was calculated to be 3.6 dB significantly from the results of surveys taken in 1964 and 1973 In practice loops are normally
7.72 1994 SR-TSV-002275 BOC Notes on the LEC Networks TransmIssion issue April 1994
measured for loss between dial-up 90042 tone source in the serving end office and due office test set at the demarcation point Such measurements include losses to wiring
the termination is as well as the minor impedance mismatch that occurs when test-set
600 instead of 900 thus these measurement results may differ from calculated values
of the 1980 survey restricted to long loops found that approximately percent With the measured losses exceeded 8.5 dB and that percent exceeded 10 dB design rules in effect at that time small percentage of loops was expected in the range of 8.5 to 10 Under no 10 dB with none greater than dB RRD rules properly designed loop
should have more than 8.5 dB of loss at kHz According to the 1983 survey results
are for the ISDN DSL about 98 percent of all nonloaded loops usable standard
7.15.9 BasIc Exchange Telecommunications Radio Service/Basic Exchange Radio Service
been in the for In recent Radio systems have used past special loop applications years the FCC has established frequency allocations to be used by radio systems to provide
isolated locations that be too to serve loop facilities to customer would costly by conventional wire DLC or radio methods As referred to by the FCC Basic Exchange Telecommunications Radio Service BETRS is also known as Basic Exchange Radio BEXR service
7.16 interoperatlon with Other Networks
7.16.1 SwItched Exchange Access
Switched exchange-access arrangements are provided for originating or terminating interLATA telecommunications They interface with an IC at POT and can route to an
end office either directly or via an access tandem
LECs offer several switched-access arrangements called feature groups Feature groups ordered the ICs differ in transmission performance and signaling capabilities and are by Area or other users according to user needs LECs also provide Wide Telecommunications Service WATS Access Lines WALs Transmission
considerations for Feature Groups through and WALs are discussed in the following
paragraphs
7.16.1.1 Access Connections
in 7-25 The following exchange-access connections are shown Figure
connection from end office to the IC POT provided by Direct InterLATA or Connecting DIC trunk This connection provided under Feature Groups
offers trunk-side access at the end office
7-73 SR-TSV-002275 BOC Note on the LEC Networks 1994 Issue AprIl 1994 Transmission
Connections from end office and end office to the IC POT via an access TCT that tandem In both cases trunk-side access is provided at the end office to trunk connects to the access tandem Tandem InterLATA Connecting TIC connection be connects the access tandem to the IC POT This overall can provided
under Feature Groups or
under connection from the line side of end office to the IC POT provided
Feature Group
tandem connection from the trunk side of end office to the IC POT via sector the sector and an access tandem In this case TCT connects the end office to tandem and an iTT connects the two tandems This arrangement would be provided not available under Feature Group when direct TCTs to the access tandem are
the characteristics of switched exchange-access Four transmission types describe
at IC POT and has the least services Type provides 2-wire interface the stringent 2- IC interface and has parameter limits Type involves either or 4-wire than is similar to transmission limits that are generally more stringent Type Type 4-wire interface and has the highest but with higher performance Type Al involves requirements
Several 4-wire interfaces at the IC POT are offered
Voice frequency
and fiber rates Digital at DS1 DS1C DS2 DS3 or DS4
levels Analog carrier at the group supergroup or master group
of Of these the voice-frequency DS2 DS4 and analog-carrier interfaces are mainly
transmission is the historical interest Note that provision of these types dependent upon
following factors
feature The particular group
Interface type
Availability of exchange-carrier facilities
for various switch-to-switch In the following paragraphs typical ICLs are given the IC connections With some exceptions in Feature Group and services designs of Actual are in the form of allowable ranges are within these objectives requirements of Feature it is the levels at the POT and the end office In the case Group of access In all cases however the responsibility of the IC to design to ensure equality carrier in these objectives ends at the IC POT responsibility of the exchange meeting
7-74 SOC Notes on the LEC Netwoilce 1994 SR-TSV-002275 Transmission Issue AprIl 1994
Legend
Access Tandem
CPE Customer-Premises Equipment
End Office EO
IC Interexchange Carrier
ITT Intertandem Trunk
POP Point of Presence
Sector Tandem
Connections Figure 7-25 Exchange-AccesS
7-75 SR-TSV-002275 BOC Notes on the LEC Networks 1994 1994 Transmission Issue AprIl
Feature Group FGA
transmission between the IC Exchange access under FGA provides voice path Point POT and the line side of an end office The end office constitutes the First connections be made Of Switching FPOS in the LATA Switched may directly network to an to an end user served by the same end office or via the intraLATA connections end user served by another end office in the LATA These are illustrated in Figure 7-26 FGA is commonly used to support foreign exchange and
similar services Transmission parameter limits are specified to the FPOS
Line-Side Termination
IritraLATA Network To Other EOs Level Parameters Per TR-NWT-000334
Transmission Parameters Not Specified Transmission Type or
EO End Office
IC Interexchan9e Carrier
EQ PoP Point of Presence
FIgure 7-26 Feature Group
Feature Group FGB
transmission between the IC Exchange access under FGB provides voice path to end user POT and the trunk side of the FPOS within LATA Access is gained acts subtending connections either directly or if the FPOS as tandem through 7-27 shows that FGB end offices via the intraLATA network For example Figure to end office could be provided by connecting the IC POT to end office directly via an access tandem or to end office via an access tandem and sector tandem
The are from the FGB is provided with type-B transmission parameters specified to the IC POT to the FPOS with the exception of an overall balance requirement
loss is for end office for connections via tandem switch The nominal dB switch The nominal direct connections between the FGB end office and the IC and the IC switch loss is dB for connections between the FOB access tandem where voice- Exceptions to these loss values may be necessary in cases nongain used where the IC them frequency facilities or combination trunks are or requests
7-76 the LEC Networks 1994 SR-TSV-002275 BOC Notes on TransmissIon Issue Apr11 1994
FGB well as FGC and are split Transmission parameter specifications for as FGD used More limits are into two tiers based on the type of facility stringent placed channel banks or on facilities using newer-type digital systems D2 through D5 cable extensions of one equivalent These facilities may include voice frequency with cable extensions of mile or less All other facilities including those greater
limits Note that the of facility used is than one mile carry less stringent type carrier dependent upon availability from the exchange
SW-to-SW ICL dB w/Gain AT to EQ Via The IntraLATA Network Digital or Analog 1.0 dB Which May include Sector Tandem CombinatIon 0-4.5 dB Nongain Transmission Parameters Not Specified Transmission Type Bi
Trunk-Side Terrni
EQ EQ SW-to-SW ICL 3.0 dB w/Gain 0-4.5 dB Nongain Transmission Type Bi
Legend AT Access Tandem
EQ End Office
IC Interexchange Carrier POP Point of Presence ST Sector Tandem SW Swftch
Figure 7-27 Feature Group
Feature Group FGC
from end office until FGD FGC access is provided only to ATT particular
at FGC is discontinued use equal access is available which time Consequently declined in recent of this offering has substantially years
7-77 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue 1994 Transmission April
Exchange access under FGC provides voice transmission path between an ATT POT and an end office As shown in Figure 7-28 access is provided through
trunk-side switching at an end office or an access tandem All segments of FGC connections are provided with Type-B transmission
loss are not included Because of the limited application of FGC facility objectives found in Switched in this document Loss specifications can be TR-NWT-000334 Combinations.21 Access Service Transmission Parameter Limits and Inteiface
EO
AT Access Tandem EO EndOffice
IC lnterexchange Carrier
POP Point of Presence SW Switch
Figure 7-28 Feature Group
Feature Group FGD
IC POT and an end Exchange access under FGD provides transmission between an office As shown in Figure 7-29 LATA access is provided through trunk-side
end office is switching at an end office or access tandem if access to an provided the via an access tandem Type-Al transmission is provided on both segments of
connection Direct access to an end office is provided with Type-B transmission
transmission and FGD provides the equal-access arrangement to all ICs The and echo maintenance plans are intended to ensure that the quality loss noise the end user to be performance furnished to all ICs by LEC will be perceived by via an access tandem equal regardless of whether access is provided directly or
7-78 the LEC Networks 1994 SR-TSV-002275 BOC Notes on Transmission Issue ApflI 1994
AT Access Tandem EO End Office
IC Interexchange Carrier
POP Point of Presence SW Switch
Figure 7-29 Feature Group
such that the The equal-access requirement of FGD necessitates loss plan is transmission loss from the end office to the IC switch via an access tandem equal trunks to the loss via direct path Equal transmission is achieved when are Additional are designed as specified in Table 7-12 design specifications provided
in TR-NWT-000334
Table 7-12 FGD Design Loss dB
ICSwitchType EOtoIC ICtoEO
Digital
Analog TPO
Analog TP2 Notes
These losses are between the end office EO access
line loop interface and the center of the IC switch
is used in the access If cable facility without gain
connection the loss can vary by dB
7.79 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Transmission
7.16.1.2 WATS Access Lines
customers demarcation WAL service provides voice transmission path between point of screening or Centrex switch and WATS central office switch capable performing
is offered in connection with FGC functions for WATS As shown in Figure 7-30 it only
for service or FGD WAL service is arranged originating calling WATS-type
terminating calling 800-type service or 2-way calling
4-wire interface at the At the demarcation point WAL is provided with 2- or option when the of the IC At the WATS central office line termination is provided except ordered dialed number- following options that require trunk termination are identification services answer supervision or EM supervisory signaling
standard 2-wire WALs are provided with three transmission types 2-wire improved 2-wire and 4-wire Standard 2-wire WALs have maximum loss of 7.5 dB Improved WALs have maximum loss of 4.5 dB Improved 2-wire WALs also provide improved
attenuation distortion and optionally improved echo performance
and echo Four-wire WALs offer further improved attenuation distortion performance loss The nominal loss and they allow the IC some flexibility in determining circuit
value for 4-wire WALs is dB
7.16.1.3 Transmission Performance Limits
The Transmission limits for access services are specified in TR-NWT-000334 transmission include loss deviation attenuation parameters that are defined for voice limits are distortion slope C-message noise C-notched noise and echo Separate given
tiers where for transmission types Al and for each of the facility-dependent
applicable
limits and Transmission limits in TR-NWT-000334 are given as acceptance IALs maximum value or deviation from Comparable to PSL an acceptance limit is the of IC An IAL is the bound design parameter that is allowed at service turnup or acceptance which immediate corrective action of acceptable performance and the threshold beyond should be taken
levels at the IC POT TR-NWT-000334 also provides ranges for expected transmission the interface code the and at the LEC switch These ranges depend on particular
transmission type and the feature group
that affect data transmission Finally TR-NWT-000334 specifies analog parameters Delay Distortion These include signal-to-C-notched noise ratio at data level Envelope EDD impulse noise intermodulation distortion and phase jitter
that differ from those LECs may elect to establish and support technical standards
provided in TR-NWT-000334
7-80 LEC Networks SR-TSV-002275 BOC Notes on the 1994 Transmission Issue Apr11 1994
Demarcation Point or WATS CO Centrex Feature Groups
2-Wire CorD
to IC
Demarcation Point or WATS CO Centrex Feature Groups or
4-Wire Lt to IC
Legend CO Central Office
Figure 7-30 WAL Service Configurations
7.16.1.4 InterLATA Directory Assistance
shown in 7-31 Directory assistance for interLATA traffic is Figure
via access Connection from the IC POT to an ACD can be made by direct path or an
traffic tandem This service can be provided with FGC and FGD Directory-assistance
also via FGB However incoming to an access tandem can be provided only cannot the desired transmission Type 4-wire is used since Type 2-wire provide with contrast between intra- and interLATA quality and will present the operator
directory assistance calls
TICs in TR-NWT-000334 Provision of directory Requirements for the are provided the and on the availability of assistance via FGB is at the option of LECs depends
facilities and switching capability
7-81 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Transmission Issue AprIl 1994
Feature Groups Access Tandem BCD May Be Feature Groups OR
liT 0.8 dB TIC Transmission Type or 4-Wire Only
Feature Groups CorD
ACD Automatic Call Distributor
DA Directory Assistance IC Interexchange Carrier ITT Intertandem Trunk POP Point of Presence TIC Tandem InterLATA Connecting Trunk
FIgure 7-31 InterLATA Directory Assistance
7.16.2 Interconnection with Private Networks
networks of Private Branch Large customers often operate their own consisting Exchanges PBXs interconnected by tie trunks These trunks may use facilities supplied PBXs be customer-owned by LECs and/or ICs or privately owned facilities The may or service an alternatively the PBX functions may involve Centrex provided by exchange carrier switching office
Private network connections to intraLATA networks are made via traditional PBX central office trunks that are line-side connections at the end office and provide either 1- way or 2-way service In addition trunk-side connections to the end office are provided
7-82 the LEC Networks 1994 SR-TSV-002275 BOC Notes on TransmIssion Issue April 1994
is made for for Direct Inward Dialing DID applications Increasingly provision being connection to PBXs on DS1 24-circuit basis
loss for The Telecommunications Industry Association TIA has developed plan
interfaces to connect to facilities The plan is MPBXs that is PBXs that use ji.-law digital contained in ANSI standard TIA/EIA-464-A-1989 Private Branch Exchange PBX
It should be noted that this loss Switching Equipmentfor Voiceband Application.22 plan between the of PBX for the various available port- specifies losses to be placed ports
to-port connections
in the customer and are based on factors such as Facility losses are determined part by PBXs to network architecture FCC Part 68 Rules see Section 13 apply to connecting
Detailed for facilities by exchange carriers to public facilities specifications provided network customers are contained in IntraLATA Voice Grade private TR-NWT-000965 Private Line Services Transmission Parameter Limits and Interface Combinations
intraLATA23 and TR-NWT-000335 Voice Grade Special Access and IntraLATA
Private Line Services Transmission Parameter Limits and Interface Combinations
exchange access
7.16.3 InterconnectIon with Cellular Mobile Radio Networks
Wireless Services Providers WSPs provide end-link telephone service to their The is customers via radio links from WSP Wireless Switching Center WSC WSC Details interconnected to the LEC network to reach regular telephone customers are
given in Section 16
7-83 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Transmission
7-84 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Trenemlsslon Issue ApclI 1994
Ref erences
ANSIJEJA 470-A-1987 Telephone Instruments with Loop Signaling
ANSIIIEEE STh 661-1979 Methods of Determining Objective Loudness Ratings
of Telephone Connections
ANSIIIEEE STD 743-1984 Methods and Equipment for Measuring the
Transmission Characteristics of Analog Voice Frequency Circuits
TR-NWT-000507 Transmission Section Issue Belicore December 1993 module of LSSGR FR-NWT-000064
ST-TEC-000052 Telecommunications Transmission Engineering Textbook
Volume Facilities Third Edition Issue Beilcore May 1989
ST-TEC-000051 Telecommunications Transmission Engineering Textbook
Volume Principles Third Edition Issue Beilcore August 1987
Parameter TR-NWT-000341 Digital Data Special Access Service Transmission
Limits and Intepface Combinations Issue Beilcore February 1993
TR-INS-000342 High-Capacity Digital Special Access Service Transmission
Parameter Limits and Interface Combinations Issue Bellcore February 1991
TR-TSY-000534 Data Services Public Switched Digital Service Issue of Beilcore July 1987 plus Revision April 1991 module ISSGR FR Nwr-000064
10 ANSI TIA/EIA-596-1993 Network Channel Terminating Equipment for Public
Switched Digital Service
11 TR-880-22135-84-01 Circuit Switched Digital Capability Network Access
Inteiface Specifications Issue Beilcore July 1984
12. TR-EOP-000277 DATAPATHTM Network Access Interface Specification Switched
Network Compatibility and Performance Specifi cations for 2-Wire Connection to
Public Switched Digital Network Issue Beilcore September 1985
Public Switched 13 SR-NWT-002598 Clarification of the Requirements for Digital Service PSDS Issue Beilcore February 1993
14 TR-NWT-000938 Integrated Services Digital Network ISDN Network Issue Transmission Interface and Performance Specifications Beilcore April 1993
Limits 32 15 ANSI Tl.501-1988 Network Performance Tandem Encoding for Modulation National Standards kbitls Adaptive Differential Pulse-Code American
Institute 1988
Bell Technical 16 Huntley Transmission Design of Intertoli Trunks System Journal Vol 32 Sept 1953 pp 1019-1036
7-85 SR-IS V.002275 BOC Notes on the LEC Networke 1994 1994 Trensmisslon Issue AprIl
17 ANSI T1.508-1992 Network Peifonnance Loss Plan for Evolving Digital
Networks American National Standards Institute 1993
18 ANSI EIAITIA 579-1991 Acoustic-To-Digital and Digital-To-A coustic
Transmission Requirements for ISDN Terminals
19 FR-N WT-00027 OSSGR Operator Services Systems Generic
Requirements Beilcore 1994 Edition
20 TA-NWT-000314 Generic Requi rements for Telephone Headsets at Operator
Consoles Issue Beilcore November 1993
21 TR-NWT-000334 Switched Access Service Transmission Parameter Limits and Issue March Interface Combinations Beilcore 1993
22 ANSI EIAITIA-464-A-1989 Private Branch Exchange PBX Switching
Equipment for Voiceband Application
23 TR-NWT-000965 IntraLATA Voice Grade Private Line Services Transmission Issue December Parameter Limits and Interface Combinations Beilcore 1991
24 TR-NWT-000335 Voice Grade Special Access and IntraLATA Private Line
Is Services Transmission Parameter Limits and Interface Combinations sue
Beilcore May 1993
NOTE
their citation in this document reflects All Beilcore documents are subject to change and advised to the most current information available at the time of this printing Readers are
check current status and availability of all documents
To obtain Beilcore documents contact
Beilcore Customer Relations
Corporate Place Room 3A-184
Piscataway NJ 08854-4156 1-800-521-CORE
908 699-5800 for foreign calls
document coordinator and Beilcore BCC personnel should contact their company obtain documents personnel should call 908 699-5802 to
To obtain ANSI documents call 212 642-4900
To obtain EIAITIA documents call 202 457-4966
To obtain IEEE documents call 1-800-678-4333
ITU switchboard at To obtain ITU-T formerly CCiTT documents call the and sales 41 22730 5111 and ask for document publication
7-86 the LEC Networks 1994 SR-TSV-002275 BOC Notes on TransmIssion Issue AprIl 1994
Bibliography JSDN Acoustic-To-Digital and Digital-To-Acoustic Transmission Requi rements for
Terminals ANSI EIA1IA 579-1991
Network Access TR-880- Circuit Switched Digital Capability interface Specifications
22135-84-01 Beilcore Piscataway NJ July 1984
Service Clanfi cation of the Requirements for Public Switched Digital PSDS SR NWT-002598 Beilcore Piscataway NJ February 1993
DATAPATH Network Access Interfrsce Specification Switched Network Compatibility Public Switched and Performance Specifications for 2-Wire Connection to Digital Network TR-EOP-000277 Beilcore Piscataway NJ September 1985
Data Services Public Switched Digital Service TR-TSY-000534 Beilcore Piscataway
NJ July 1987
Access Service Transmission Parameter Limits and Interface Digital Data Special 1993 Combi nations TR-NWT-000341 Beilcore Piscataway NJ February
TA-NWT-000314 Generic Requi rements for Telephone Headsets at Operator Consoles Beilcore Piscataway NJ November 1993
Parameter Limits and High-Capacity Digital Special Access Service Transmission 1991 interface Combinations TR-INS-000342 Beilcore Piscataway NJ February
Bell Technical Huntley Transmission Design of Intertoil Trunks System Journal Vol 32 September 1953
Transmission and Integrated Services Digital Network ISDN Network Interface NJ 1993 Performance Specifications TR-NWT-000938 Beilcore Piscataway April
IntraLATA Voice Grade Private Line Services Transmission Parameter Limits and Beilcore Piscataway NJ December 1991 Interface Combinations TR-NWT-000965
Methods and Equipmentfor Measuring the Transmission Characteristics of Analog Standard Voice Frequency Circuits ANSIIIEEE 743-1984
Connections Methods of Determining Objective Loudness Ratings of Telephone ANSLIEEE Standard 661-1979 ANSI Network Channel Terminating Equipmentfor Public Switched Digital Service TLAJEIA-596- 1993
ANSI Standard Network Performance Loss Plan for Evolving Digital Networks T1.508-1992 American National Standards Institute 1993
Network Performance Tandem Encoding Limits for 32 Kbitsls Adaptive Differential Pulse-Code Modulation ANSI Standard T1.501-1988 American National Standards
Institute 1988
FR-NWT-00027 Beilcore OSSGR Operator Services Systems Generic Requirements
Piscataway NJ 1994 Edition
7-87 BOC Notes on the LEC Networks 1994 SR-IS V.002275 1994 Transmission Issue April
Voiceband Private Branch Exchange PBX Switching Equipmentfor Application ANSIIEJAITJA-464-A- 1989
Switched Access Service Transmission Parameter Limits and Inteiface Conthinazions
TR-NWT-000334 Belicore Piscataway NJ March 1993
ANSIIEIA-470-A-1987 Telephone Instruments with Loop Signaling
Transmission Section TR-NWT-000507 Beilcore Piscataway NJ December 1993
Telecommunications Transmission Engineering Complete Volume Set ST-TEC
000063 Third Edition Beilcore Piscataway NJ July 1990
Services Transmission Voice Grade Special Access and IntraLATA Private Line
Parameter Limits and Interface Combinations TR-NWT-000335 Beilcore Piscataway NJ May 1993
7-88
BOC Notes on the LEC Networks 1994 SR-TSV-002275 Contents Issue AprIl 1994
Section
Operations and Maintenance Contents
81 Operations and Maintenance 8-1 8.1 8-1 8.1.1 Maintenance Objective 8-1 8.1.2 Network Evolution 8-2 8.2 Trunk Maintenance 8-3 8.2.1 Digital Trunk 8-3 8.2.2 Trunk Types 8-3 8.2.3 Steps for Effective Trunk Maintenance 8-3 8.2.3.1 Trouble Detection 8-4 8.2.3.2 Service Protection 8-5 8.2.3.3 Trouble Verification 8-6 8.2.3.4 Sectionalization 8-6 8.2.3.5 Repair 8-6 8.2.3.6 Repair Verification 8-6 8.2.3.7 Restore to Normal 8-7 8.2.4 Test Positions 8-7 8.2.4.1 Operational Tests 8-8 8.2.4.2 Transmission Tests 8-8 8.2.5 Test Lines 8-9 8.2.5.1 Transmission Test Lines 821 8.2.5.2 Operational Test Lines 8-24 8.2.6 CAROT System Test Unit 8-28 8.2.7 Remote Trunk Test UnitlCentral Trunk 8-29 8.3 Common Channel Signaling 8-30 8.3.1 CCS Maintenance Plan 8-30 8.3.2 Node Maintenance 836 8.3.3 Signaling Link Maintenance 8-36 8.3.4 CCS Interface 8-36 8.3.5 Present Link Testing Strategy 8-37 8.3.6 Link Circuit Parameters 8-37 8.3.7 Data Service Unit Test 8-41 8.3.8 Network Maintenance 8-41 8.3.9 Link Maintenance Flow 841 8.4 Switch Diagnostics 8-43 8.4.1 Digital Systems 8-44 8.4.2 Digital Switch Alarms 8-44 8.4.3 Network Synchronization...... - with Carrier 8.4.4 1E/1A ESS Switch Equipped Digital 8-45 Terminal Trunk 8-45 8.4.5 Automatic Operational Testing SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Contents
8-46 8.4.6 Performance Monitoring 847 8.4.7 Transitional Strategies 8-48 8.4.7.1 Switch Surveillance 8-48 8.4.7.2 CAROT 8-49 8.4.7.3 Carrier Group Alarms 8-49 8.4.7.4 Switch Threshold Settings 8-49 8.4.7.5 Miscellaneous Arrangements 8-50 8.5 Switching System Maintenance 8-50 8.5.1 Switching Control Center 8-51 8.5.2 Electronic Systems Assistance Center 8-51 8.5.3 SPC-SCC Operations Systems 8-51 8.5.4 Electromechanical SCC Operations Systems 8-51 8.5.5 Automatic Trouble Analysis System 8-52 8.6 Memory Administration 8-52 8.6.1 Provisioning-Driven Memory Administration PDMA 8-52 8.6.2 System Administration 8-52 8.6.3 Memory Backup and Restoration 8-53 8.7 Facility Maintenance Administration Center 8-53 8.7.1 Facility Maintenance and 8-53 8.7.2 Operations Support Systems 8-53 8.7.2.1 T-Carrier Administration System
8.7.2.2 Telecommunications Alarm Surveillance and
Control 8-54 8-54 8.7.3 Surveillance and Control of Transmission Systems 8-54 8.7.4 Carrier Transmission Maintenance System 855 8.8 Transport System NIaintenance Basic Access 8.8.1 Integrated Services Digital Network vIaintenance 855 8-56 8.8.2 Public Packet Switched Network Maintenance 8-57 8.8.3 Synchronous Optical Network Maintenance 8-60 8.9 Loop Maintenance .... 8-60 8.9.1 Automatic Repair Service Bureau 8-61 8.9.2 Loop Maintenance Operations System 8-61 8.9.3 Mechanized Loop Testing System 8-61 8.9.3.1 MLT-1 8-61 8.9.3.2 MLT-2 8-62 8.9.4 Loop Cable Maintenance Operations System 8-62 8.10 Planned Long-Term Network Advancement.. 863 8.10.1 Bit Error R.atio 8-63 8.10.2 Assignment of Bits in DS1 Superframe Format Signals Format 8.10.3 Assignment of Bits in DS1 Extended Superframe 864 Signals 8-65 Parameters 8.11 Digital Testing ..... 8-69 References .._ ..... 871 Bibliography
II the LEC Networks 1994 SR-TSV-002275 BOC Notes on Contents Issue AprIl 1994
List of Figures
Trunk 8-11 Figure 8-1 Test Line Arrangements for IntraLATA Testing
8-13 Figure 8-2 900-a Quiet Termination
8-13 Figure 8-3 600-a Quiet Termination
Termination Tandem Figure 8-4 1/lA ESS Switching System Quiet 8-13 State ..-.
Termination Local Figure 8-5 1/lA ESS Switching System Quiet 8-14 State
8-25 Figure 8-6 CA.ROT System
and CAROT Testing Functions of Figure 8-7 Near-End Far-End Common Equipment within an End Office for lhree Types of Test 8-27 Equipment
8-31 Figure 8-8 National Signaiing Network
Access 8-32 Figure 8-9 Access Links Database
8-33 Figure 8-10 ridge Links
Links STPs 8-33 Figure 8-11 Cross Regional
Links 8-34 Figure 8-12 Cross
8-34 Figure 8-13 Diagonal Links
Links 8-34 Figure 8-14 Fully Associated
8-35 Figure 8-15 Signaling Data Links Summary
Test Access via SMAS/SARTS 8-38 Figure 8-16 CCS 839 Fie 817 Test Access via Digital Cross-Connect System 840 Figure 8-18 DSOA Link Testing Arrangement
Maintenance Flow 8-42 Figure 8-19 Example of Link
III SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue 1994 Contents AprIl
List of Tables
83 Table 8-1 Trunk Types
8-37 Table 8-2 Test Requirements for and Digital Link Circuits
Table 8-3 Data Service Unit Test 8-37
844 Table 84 Digital Svitch Alarnis
Table 8-5 Performance Monitoring 8-47
8-63 Table 8-6 Bit Error Ratio
8-63 Table 8-7 Assignment of Bits in DS1 Superframe Format Signals
Format Table 8-8 Assignment of Bits in DS Extended Superframe 864 Signals
lv 1994 SR-T$V-002275 BOC Notes on the LEC Networks and Maintenance issue April 1994 Operations
Operations and Maintenance
8.1 Introduction
8.1.1 MaIntenance Objective
service The objective of an effective overall maintenance plan is to provide high-quality maintenance must on the network at reasonable cost To accomplish this program automated take advantage of the accuracy and speed afforded by modern Operations from consolidation of skilled Support Systems OSSs as well as the efficiencies possible
communications technicians at centralized work locations
Carrier networks have evolved to Maintenance plans for most Local Exchange LEC and centralized method of operational and administrative control Centralized databases the and work forces make it possible to effectively maintain precision stability required switched network for the current public
and of the network whole is This The sophistication of switching systems as growing with real-time trouble together with the proliferation of digital switching systems take detection and analysis capabilities requires maintenance plans and methods that can
advantage of the advanced network element capabilities
Inadequate maintenance at one switching office or center can cause excessive trouble at
that location and create an adverse reaction elsewhere in the network The switch-
connecting network has become increasingly larger in bandwidth Outages therefore the overall network have much greater effect on
is essential To preserve the network integrity well-organized maintenance plan Intercompany cooperation is necessary for coordinated maintenance of the North maintenance that defme the American integrated network Company plans clearly each work and control center facilitate the responsibilities assigned to position
cooperative maintenance of the switched network
8.1.2 Network Evolution
The continued evolution of maintenance procedures is stimulated by the implementation
of advanced technology built into OSSs and by the continued growth of the factors contribute communications network both in size and capabilities The following
to that evolution
Increased use of automated procedures and self-alarming arrangements that transmission networks automatically indicate troubles in the switching and
trouble detection More widespread use of digital switching systems with real-time
and analysis capabilities
8-1 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Operations and Maintenance
for maintenance as well as Formation of control centers that have responsibilities
associated with of central offices other operations for trunks and facilities group
Interconnection of the centralized OSSs to create an intelligent operations support
network
data the Increase in the number of customers transmitting low-speed over public-
switched trunking network
retain level of The creation of control centers has permitted personnel to high expertise In to various and difficult maintenance problems addition because of greater exposure broader view of the network which can be personnel at the centers are afforded troubles that affect number of elements in the beneficial in detecting and repairing network
centralized trunk and Many LECs have organized maintenance efforts so that switching of the Control Center system maintenance functions are the responsibilities Switching
Personnel at the work centers are into SCC in the exchange environment organized Each work is particular set of maintenance work positions and teams position assigned automated functions and is generally supported by an system
handled Work Station where Trunk-related problems are by Trunk IWS correct technicians perform manual and routine tests on circuits to problems for trunk transmission Trunk Operations Support Center TOSC is responsible administration of corrective action problem identification and
be monitored directed and administered from centralized Facility maintenance may locations In areas with high concentration of T-carrier facilities Facility Maintenance and Administration Center FMAC directs and coordinates the facilities activities associated with restoration of service using spare
more using In addition Network Operations Centers NOCs are becoming widespread Electronic Assistance Center and the support groups such as the Systems ESAC These surveillance Network Management Center NMC centers typically perform elements and are more centralized than SCCs functions on transport and network
environment with self- As the network continues to evolve toward fully digital planned in the network workplaces may become checking and self-healing capabilities changes of the new environment necessary to take full economic and technological advantage
8.2 Trunk Maintenance
accessible to traffic that they The trunk maintenance process ensures that trunks are and termination and that they provide proper function properly during call setup
transmission path during the call
conducted from test Trunk maintenance procedures may involve manual operations via the Centralized Automatic Reporting On position as well as fully mechanized testing these instances test lines provide Trunks CAROT system and switch diagnostics In
far-end test termination functions
8-2 LEC Networks 1994 SR-TSV-002275 BOC Notes on the one and Maintenance Issue April 1994 Operati
8.2.1 DigItal Trunk
combined with The increase in the number of digital switches in the network heavy and has made it to define trunk to concentration of digital facilities necessary digital to ensure that the trunks are properly examine existing trunk maintenance plans digital monitored and tested The increased use of the switched-message network to transmit for trunk maintenance Trunk data has demanded new methods and operating procedures
that the network will low- maintenance plans must ensure switched-message support speed data as well as voice transmission
interoffice trunk originating and digital trunk is defmed as an switched-message with terminating in digital switches connected by digital facility no analog/digital conversion
8.2.2 Trunk Types
exist in the network Table 8-1 illustrates the trunk types that
Table 8-1 Trunk Types
Trunk Types Orig Office Facility Term Office
Analog
Combined
Digital
AMalog DDigital
8.2.3 Steps for Effective Trunk Maintenance
8.2.3.1 Trouble Detection
both the detection of trouble and reference Trouble detection for message trunks requires Service mandate identification of to the responsible maintenance organization goals Performance immediate troubles as soon as they occur monitoring may provide routine is still required to detect analog detection capabilities however CAROT testing
8-3 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April1994 Operations and Maintenance
until trunk troubles and to provide C-notched noise results on digital trunks performance end-to-end monitoring is improved and deployed with capability
trunks maintained the following activities Digital and combination are by
Performance monitoring is used where available
Routine testing CAROT continues
fill the Routine Bit Error Ratio Testing BERT has been deployed in some areas to
performance monitoring gap in this transitional period
in network elements and OSSs of Performance monitoring capabilities exist Examples network elements that have some performance monitoring capability are
Digital switches
Digital Carrier Terminals DCTs
Digital multiplexers
devices that be attached number of vendors manufacture performance monitoring can
available an to digital facilities with monitoring results through operations system
results The trunk maintenance organization needs all available performance monitoring
to assist in the trunk maintenance effort Often the required performance monitoring
information is not directed to them More interaction between the trunk maintenance the switch maintenance and facilities maintenance organizations is dictated by merging
of technologies
routine and Analog trunks continue to be maintained by all CAROT testing transition to network administrative operations It is anticipated that as the fully digital trunks will be decreased to small fraction environment continues the number of analog trunk maintenance of total trunks This will begin the age of all-digital trunks and of
based on network performance monitoring
8.2.3.2 Service Protection
that failed or trunk be taken out of service Service protection requires degraded for and combination trunks is handled as follows Service protection digital
Automatic removal from service for an indication of red or yellow alarm
Manual removal from service based on referral from other maintenance
organizations such as FMAC
Sometimes referred to as Bit Error Rate
8-4 BOC Notes on the LEC Networks 1994 SR.TSV-002275 Operations end Maintenance Issue April1994
as determined red or yellow alarm Failure of trunk line 1.544 Mbps Ti system by affected switched trunks will automatically remove from service the message
Alarm either from channel bank or Red alarms are initiated by Carrier Group CGA Some switches have the capability to remove as calculated by the digital switch may condition and/or trunks from service based on an Out-of-Frame OOF slips
switches and use the Each LEC must be aware of the capabilities of the digital deployed
available parameters
OOFs have minimal effect While CGA will affect both voice and data slips and may however cause customer line on voice while affecting data transmission Slips may cutoffs
of Carrier Failure Alarm CFA CGAs are provided to notify maintenance personnel involves the trunk out of and to allow trunk conditioning Trunk conditioning taking from trunks served by failed or degraded service to prevent customers accessing
facility
detected in either direction of Trunk conditioning should occur when CFA is indication trunk transmission This is accomplished by giving the appropriate per group has cleared Trunks should automatically be restored to service when the CGA
switches several conditions must be correct for In analog Stored Program Control SPC
trunk conditioning to take place properly
to master scanner in The CGA on the channel bank must be cross-connected point
the switch
translated in the switch to correspond to CGA The master scanner point must be number
translated in the switch to correspond The Trunk Network Numbers TNNs must be
to the CGA number
8.2.3.3 Trouble Verification
trunk trouble exists retest of the suspicious Trouble verification is validation that
before removing it from service trunk or trunks is made manually
and trunks is handled as follows Trouble verification for digital combination analog
and access troubles Perform CAROT tests to verify transmission
data tests to switched data impairments Perform manual digital or voice-grade verify
troubles and/or hard failures CAROT provides Tests are conducted to verify marginal and access with the mechanized test but is limited to analog impairments problems which indicate digital impairment exception of the C-notched-noise parameters may switched data should be verified by performing Troubles that are reported to be affecting
manual digital testing
8-5 SR-TSV-002275 BOC Notes on the LEC Networks 1994 issue April 1994 Operations and Maintenance
8.2.3.4 Sectionalization
is to determine if the trouble is switch- or facility- The first step in sectionalization related Once this has been determined the trouble may be referred to the proper maintenance force for further sectionalization
handled follows Sectionalization for digital and combination trunks is as
Use OSS information to indicate network troubles
Perform demand tests and pattern results
aid in trunk troubles Systems OSS testing capability can dramatically sectionalizing Facilities such as Beilcores NMA system and Northern Telecoms Digital Management System DFMS are examples of OSSs designed for this capability Again and the facilities close interaction is needed between the trunk maintenance organization organization
useful for to or switch Demand testing via CAROT can be pointing digital facility All trunks on can be tested trouble on particular trunk or trunk group given facility
indicated If one individual trunk is failing If they all fail facility problem is only switch or channel problem is indicated
handled demand Switching machine sectionalization for analog trunks is by performing tests and patterning results
8.2.3.5 Repair
be Repair of switched-message trunk demands that the trouble once sectionalized for further isolation and This requires referred to the proper maintenance group repair and/or location For interaction and coordination between more than one organization
and trunks the will depend on the operational and digital combination analog procedure
administrative organizations of the LEC
8.2.3.6 Repair Verification
verification The same procedures are used here as for trouble
8.2.3.7 Restore to Normal
is the affected trunks be manually returned to When repair verification complete may to confirm that the trouble condition has service Additional monitoring may be required been cleared
NMA is trademark of Beilcore
8-6 SR-TSV-002275 BOC Notes on the LEC Networks 1994 and Maintenance Issue AprIl 1994 OperatIons
8.2.4 Test Positions
of associated with manual trunk Test positions provide an assortment capabilities testing in their level of and features The capabilities vary substantially sophistication provided The depending on the type and vintage of the switching system and local practices transmission fundamental functions of test position are to provide access to trunks for
and to control the maintenance state is availability for and operational testing that
of trunks or at service of the trunks Test positions are normally located at the ends
centralized control location
with Trunks can be accessed for manual testing by either jack arrangements associated
controlled the direct access to the trunk or by special switching-access arrangements by
associated SPC switching system Jack access is employed on certain testboards
associated with older electromechanical switches Switched access is used with
common-control electromechanical or SPC switching systems In electromechanical trunks and the of trunks can switching systems only the outgoing outgoing portion 2-way and be accessed In SPC and digital systems all trunks incoming outgoing 2-way can be accessed
monitor the trunks tested and to All test positions have the capability to talk over or being
perform certain transmission operational and signaling tests Tests may be conducted line The between two different test positions or between test position and test maintenance state of the trunk may be controlled at trunk test position For example be in out-of- trunk may be made active or available for service or it may placed an
service state
In addition access to control the signaling on trunk from test position is generally
be controlled and provided The outgoing supervision on- or off-hook can monitored
and the incoming supervision may also be monitored In addition the ability to outpulse
is multifrequency pulsing dial pulsing and dual-tone multifrequency signaling the while the provided Stress-signaling test conditions may be applied to near end far end with results to detect signals received at the are compared expected marginal further and troubles Trunks that do not pass this pulsing test are subjected to analysis of repair Measurements of dc trunk characteristics resistance capacitance and voltage
trunks can be performed by switching systems that connect trunks through conducting
paths to test positions
8.2.4.1 Operational Tests
function on Operational testing features are provided at test positions The ring-forward
test circuit test trunks is tested by termination at supervisory and signaling 103-type line Ringing tripping and supervisory functions on incoming trunks are tested via
synchronous and nonsynchronous test lines
8-7 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Operations and Maintenance
8.2.4.2 Transmission Tests
be and controlled by the test For transmission testing of trunks test signals can originated
include 1004 Hz at or 16 dBrn0 position These originating test signals 10 Transmission measurements 404 Hz at 16 dBmO and 2804 Hz at 16 dBmO
should include all of those tests in performed at receiving-end test position specified TR-NWT-000334 Switched Access Service Tran.mission Parameter Limits and be conducted between one test Interface Combinations.1 Transmission tests may
and another for trouble sectionalization or from test position to position jarticularly far-end test line
all of the above for each of On-site trunk test positions provide most or capabilities type trunk maintenance central office For certain types of offices there are associated remote the centralized locations that of the testing functions found at positions at provide many on-site positions
8.2.5 Test Lines
the basic for the maintenance of trunks Test lines in Test lines are part of plan range to those the complexity from those providing simple tones and terminations providing
tests and transmission tests relatively complex functions of applying marginal signaling received and recognizing and replying to specific signals
accessed from manual All of the test lines discussed in the following paragraphs can be
control features not found in all test positions although some might require positions limited to modern of The following descriptions are generally more implementations
each test-line type
Test lines are currently accessed by
to the Tandem office intertandem trunks 3-digit lox code corresponding
specific type of test line
code Tandem office intertandem connecting trunks 3-digit end office NXX
NIXX codes available in Numbering Plan Area assigned from the spare NPA
End offices 7-digit subscriber number
received in some machines the incoming trunk For transmission test lines the digits and
class are used by the switching system to
Connect to the proper type of test line
and transmission-level point Choose line of the proper signaling type impedance
simulate local-terminating or Place the incoming trunk unit in the correct state to
through-switched call
958 and are reserved for testing The Two exchange number NNX codes 959 purposes communications between offices This code can code 958 is typically used for switching
line that terminates on test frame or switchpersons be used to provide access to test
8-8 SR-IS V-002275 BOC Notes on the LEG Networks 1994 and Maintenance Issue AprIl 1994 OperatIons
for both and desk These test locations are provided with the means originating Calls directed terminating calls for handling intermachine troubles are by outpulsing up or the and to nine digits that include the NPA and OXX code NPA OXX 958 NPA code an thousands digit followed by the test line 958-1XXX
four additional is for access to office Currently the code 959 plus three or digits assigned Carrier offices test lines in Bell Operating Company BOC and Interexchange IC
Test lines should not be seized until the originating office has completed pulsing
is unless off-hook Following seizure or ring trip off-hook supervision provided off-hook test lines that supervision is part of the test sequence Following supervision the units send tones provide quiet period of 300 ms to permit single-frequency signaling to change supervisory state refer to Section of this document
at timed intervals to facilitate In many cases periods of on-hook supervision are applied end has disconnected Most test lines taking down the connection once the originating can be optioned to remove tone during these periods to ensure proper single-frequency signaling unit operation
control circuits To provide supervision test lines typically have supervisory for example holding coil and relay that may be in the transmission path These control transmission in the circuits are designed to have negligible effect on the specifications voiceband
The stated frequencies of test-line tones include an additional Hz above the nominal that be in Pulse-Code frequency to avoid the modulation byproducts may produced Modulation PCM-type carrier
8.2.5.1 Transmission Test Lines
facilitate to 100 Test Line The 100 test line is in industry-wide use to connection of There are two termination for balance and noise testing see Part Figure 8-1
general versions of the 100-type test line The early version provides only quiet addition the termination for balance and noise testing The later version in to quiet The of termination also provides 1-kHz tone for 1-way loss measurements parameters follows the quiet termination and 1-kHz tone are as
termination Quiet termination The quiet termination typically provides on office in series with 2.16- consisting of 900 or 600 depending impedance 8-2 and In some this termination is built out pF capacitor see Figures 8-3 cases are of the nominal office capacitance with build-out capacitor Exceptions
is 600-fl In 4-wire analog offices the quiet termination 4-wire termination
the of 600-fl 4-wire In digital offices the office provides equivalent quiet
termination
8-9 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Operations and Maintenance April
The 1/lA ESS offices have two versions of quiet termination The older
version consists of 900-el resistor in series with 2.16-jiF capacitor see
Figure 8-2 as described above The newer version is more complex with
two states tandem and local
The tandem state provides termination consisting of an 887-a resistor
in series with 2.16-jiF capacitor In some cases this termination may
be built out to the equivalent of 400 ft of office cabling junctor grouping
frame to the termination with build-out resistor and build-out
capacitor see Figure 8-4
simulate The local state provides complex impedance designed to of this typical local loop Figure 8-5 shows simplified schematic
termination In some cases the termination may be built out to the
equivalent of 400 ft of office cable
l-kHz test tones
version Frequency Several versions of mW-tone supplies exist The older
provides 1000-Hz 10-Hz tone The newer version provides 1004-Hz 1-Hz tone
Level These tones are adjusted to either 0.0 0.03 dBm Test Pad
office 2.0 0.03 dBm TP office or 3.0 0.03 dBm TP office as measured at the center of the switching machine for example trunk or line
distribution frame and junctor grouping frame
Impedance Nominal impedance of the tone source is either 600 or 900
depending on the nominal impedance of the office
Exception Digital offices may provide 0.0-dBmO synthesized 1004-Hz For information on the see digital signal digital mW more digital mW FR-NWT-000064 LATA Switching Systems Generic Requirements LSSGR.2
ESS is trademark of ATT
8-10 the LEC Networks 1994 SR-TSV-002275 BOC Notes on Operations and Maintenance Issue AprIl 1994
Near-End Far-End
Near-End Test Switching Trunk Switching Far-End Test Line Equipment System Under Test System \/ \/ To CAROl
TOiLL1___ 101-Type Test Position
109- Type
ROTL Remote Office Test Line
Trunks CAROT Centralized Automatic Reporting on
for IntraLATA Trunk FIgure 8-1 Test Line Arrangements Testing
8-11 SR-TSV-002275 SOC Notes on the LEC Networks 1994 Issue April 1994 Operations and Maintenance
IntraLATA Trunk Figure 8-1 Test Line Arrangements for Testing Continued
8-12 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Operations and Maintenance issue April 1994
90O2
Figure 8-2 900-I Quiet Termination
6002
2.161.LF
Figure 8-3 600-a Quiet Termination
Build-Out Resistor
6002
Build-Out Capacitor 2.16 i.iF
resistor and the build-out In some cases the build-out to build out the termination capacitor may be adjusted
to total of 400 ft of office cable from the connecting frame for example the junctor grouping frame
Quiet Termination Tandem State Figure 8-4 1/lA ESS Switching System
8-13 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Operations and Maintenance Issue April 1994
Build-Out Resistor
2.16p.F
8872
0.02
In some cases the build-out resistor and the build-out termination capacitor may be adjusted to build out the to total of 400 ft of office cable from the connecting
frame for example the junctor grouping frame
State Figure 8-5 l/lA ESS Switching System Quiet Termination Local
Operational parameters
The older version of the 100-type test lines provides only quiet
termination Upon seizure of the test line the operational sequences are as follows
and termination is Off-hook answer supervision is returned quiet
placed across circuit
of Some versions return short interval approximately second on-
11 hook disconnect supervision every seconds starting approximately
11 seconds after the initial connection
followed The newer versions of the 100-type test lines provide 1-kHz tone
of the the by quiet termination Upon seizure test line operational
sequences are as follows
8-14 BOC Notes on the LEC Networks 1994 SR-IS V-002275 Maintenance Operations and Issue AprIl 1994
returned Off-hook answer supervision is
is for After approximately 300-ms delay l-kHz tone applied
approximately 5.5 0.5 seconds
termination is until the After the tone is disconnected quiet applied
caller disconnects
return 1- 2- or 3-second on-hook disconnect Certain types may seconds after the termination has been signal approximately 11 quiet
applied
3-second on-hook disconnect Others may return series of 1- 2- or has 30 seconds after the quiet termination signals approximately every
been applied
and test line into 101 Test Line The 101 test line provides communication be reached over trunk incoming to the switching testboard or test position that can any
It is used for reporting that test see Part of Figure 8-1 system served by position troubles making transmission tests etc
1000- 1004-Hz tone for loss 102 Test Line Milliwatt 102-type provides or 1-way of this termination are measurements see Part of Figure 8-1 The features given below
1000- or 1004-Hz tone Transmission parameters
versions of mW-tone exist The older version Frequency Several supplies The version 1004-Hz provides 1000-Hz 10-Hz tone newer provides 1-Hz tone
either 0.0 0.03 office Level These tones are adjusted to dBm TP 2.00.03 dBm TP office or 3.00.03 dBm TP office as trunk or line measured at the center of the switching machine for example
distribution frame and junctor grouping frame
of the tone source is either 600 or 900 fl Impedance Nominal impedance of the office and depends on the nominal impedance
0.0-dBmO 1004-Hz Exception Digital offices may provide synthesized For more information on the digital mW see digital signal digital mW FR-NWT LATA Switching Systems Generic Requirements ISSGR
seizure of the test line the operational sequences Operational parameters Upon
are as follows
returned Off-hook answer supervision is
200 ma for After delay of approximately 300 ms minimum
1/lA ESS office 1-kHz tone is applied
8-15 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Operations and Maintenance April
NOTE
One older version may be optioned for 175-ms delay
The test line may be installed to provide at regular intervals ranging
between and 12 seconds either 1- 2- or 3-second interruption of tone
Some of the test lines may also provide on-hook disconnect supervision during this no-tone interval
NOTE
One older version may be optioned for 2-second interruption every minutes
104 Test Line Transmission measuring and noise checking 104 type provides test This termination termination for 2-way transmission testing and 2-way noise checking frames but may be used to test trunks from offices equipped with automatic trunk test cannot be used by the CAROT system It may also be used for manual 1-person 2-way transmission measurements from testboard or maintenance center see Part of
Figure 8-1 The 104-type test termination does the following
Provides test pads as required by the office in which it is located
Provides off-hook supervision
Measures the 1000-Hz loss of the trunk from originating end to far end
Adjusts transmitting pad to equal the trunk loss measured in If this loss
exceeds 10 dB the transmitting pad value is reduced by 10 dB and subsequent this fact the end wink signal indicates to originating
Performs two self-checks to determine if the pad has been properly adjusted In
of the is case of failure in either of these checks repetition measurement
requested
Applies 1000-Hz test power directly to the trunk to permit receiving
measurement at the originating end
After timed interval sends 1000-Hz test power through the transmitting pad
if been reduced 10 adjusted in preceded by wink signal it has by dB The
difference between the levels of the two tones received at the originating end
adjusted by 10 dB if necessary equates to the loss measured in
noise can be Provides quiet termination for seconds so that the measurement
made at the originating end
At the same time makes noise measurement at the test termination If the noise off-hook disconnect exceeds the threshold 41 dBrnC an alternating on-hook
signal is returned Otherwise steady on-hook signal is returned
8-16 SR-TSV-002275 SOC Notes on the LEC Networks 1994 and Maintenance Issue April 1994 OperatIons
105 Test Line Automatic transmission measuring test line 105 type provides far-end access to responder and permits 2-way loss and noise measurements to be made on trunks from near-end office equipped with Remote Office Test Line ROTL and responder Up to 15 105-type test lines may be associated with one common responder connection the The test lines act as parking circuits for calls awaiting to responder see
Part of Figure 8-1 The near-end ROTL and responder are directed by CAROT control unit In an controller or equivalent or manually operated ROTL integrated
105-type test line/responder unit the 105-type test line performs the responder functions in addition to its normal functions
basis each call The waiting calls are served one at time on cyclic preferential As and from 105-type test line is connected the test line provides the proper supervision impedance conversion between the trunks to be tested and the responder
The 105-type test lines provide indications to the responder regarding the impedance at which the measurement is to be made 600 or 900 and the TP required TP TP orTP
initiated and off-hook When the 105-type test line is seized the timing functions are an office supervisory signal and test-progress tone are returned to the originating Test
If the is progress tone equals 2225 Hz 25 Hz at 10 dBmO 0.5 dB responder idle
that the test line to the the chain-circuit relays operate cut-through relays connect responder and remove the test-progress tone If the responder is busy and/or other test
have been the test- lines in preferential positions in the chain circuit already seized
the end to indicate that the call is progress tone continues to be sent back to originating chain circuit has parked and awaiting cut-through to the responder When the progressed tone to the test line under consideration the test line is cut through and the test-progress is removed
Prior to connecting to responder the 105-type test line requires two or three timing intervals depending upon the type of trunks being served These timing intervals are interval of 150 provided by timing circuit incorporated in the test line The first timing
tests to ms is required in some offices to allow the marker to perform continuity prior cut-through The second timing interval of 150 ma is required to allow single-frequency
signaling units to stabilize
The third timing interval of 900 ms minimum is provided by all 105-type test lines
is returned to the that test line has been test-progress tone originating end indicating line has not seized seized If at the end of this third timing period the 105-type test
the line until the connection is made or until responder the test-progress tone remains on the connection the originating end releases
the the test After the testing sequence has been completed responder signals 105-type line remains connected to the trunk until the line to release just-released 105-type test
office time-out feature it to be originating end disconnects or until the causes
disconnected On 105-type test lines used in end offices the test line also returns an on-
line has been released from the trunk hook signal to the originating office When the test another call it restores to normal and is ready to receive test
8-17 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Operations and Maintenance
The can be used in with the Several types of responders exist lB-type conjunction of loss and noise measurements 105-type test line The 51 is capable making 2-way The responder is The 52-type responder provides additional testing capability 56A-type dial offices and Private Branch Exchanges designed for small end offices community manufactured The PBXs The SiB-type responders are no longer being responder follows testing capabilities are as
lB-type responder
Loss
C-message noise
52-type responder
Loss
C-message noise
C-notched noise
Gainslope
Return loss balance
Measure and terminate three-card option
Terminate only one-card option
56A-type miniresponder
Loss
C-message noise
C-notched noise
Gainslope
Return loss balance terminal only
Remote Trunk Test Unit RTFU all 52-type capabilities including balance measurements and terminations
connection to 107 Test Line Data-transmission test line 107-type provides signal of data and voice transmission source that provides test signals for 1-way testing The test line Peak-to-Average Ratio parameters see Part of Figure 8-1 provides and intermodulation-distortion P/AR signal gainslope frequencies quiet termination
manual in which 1-way far-to-near measurements The mini-responder provides an additional sequence be made al the near end The mini-responder of loss gainslope and C-message noise can by personnel
combines the function of single 105-type test line and responder
8-18 the LEC Networks 1994 SR-IS V-002275 SOC Notes on OperatIons and Maintenance Issue April 1994
line also allows measurements of return loss frequency shift phase test signals The test hits hits and dropouts jitter C-notched noise impulse noise gain phase
data The P/AR signal having spectrum similar to many high-speed sets permits rapid
of for data transmission The P/AR signal is particularly check of the quality facility
sensitive to envelope-delay distortion The three gainslope frequencies 1004 Hz trunk 404 Hz and 2804 Hz at 16 dBmO permit measurement of the frequency
characteristics 1004-Hz 16-dBmO tone permits measurement of frequency shift
noise hits hits and dropouts phase jitter C-notched noise impulse gain phase
termination for in- 108 Test Line Code 108 test line once provided looparound Code however has been to service testing of far-end echo suppressors 108 reassigned defined in American National Standards Institute digital circuit loopback test line as and PBXs Circuit Test ANSi Ti .206-1988 Digital Exchanges Digital Loopback Line3 and FR-NWT-000476 OTGR Section Network Maintenance Access and
the level Testing.4 This test line provides loopback at Digital Signal DSO 64 kbps
of digital circuit for analysis and repair purposes
of the 108 test line Part of Figure 8-1 shows the architecture and application
circuits for This test line is needed to verify the overall performance of switched digital
the following reasons
of data service on switched circuits For analysis of customer reports degraded
switched circuits to For repair verification of digital error performance prior
returning the circuit to service
of DSO/DS1 As preservice check to ensure proper implementation options
To establish performance benchmarks in the digital environment
and Test Pattern Generator reside in the switch as The Digital Test Receiver Digital may in OSS an adjunct to the switch similar to the ROTL or an
is needed to standard interface from operating system to network equipment or system
of automated testing of switched allow flexibility in the implementation digital DSO
message trunks
109 Test Line Echo canceler test line 109-type see Part of Figure 8-i provides echo cancelers the loopback arrangements for in-service testing of far-end Upon access after 2-second returns nominal test line returns off-hook supervision and delay seconds After an on-hook 1000-Hz or 1004-Hz tone at -10 dBmO for approximately Measurements made at the near end flash connection is made to quiet termination should indicate for this with Return Loss Measuring Set RLMS very high reading
condition
another on-hook flash is followed 6-second After approximately 16 seconds by The should interval in which the trunk is looped back with no attenuation RLMS
canceler cannot function with less than dB indicate very low reading since the echo
of return loss
8-19 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Operations and Maintenance
1O-dB for Finally after third on-hook flash the trunk is looped through pad 16 seconds The echo canceler should now function and high level of return loss will be measured The near-end canceler has no effect on these tests and must be checked each end the trunk with similar test performed with the functions reversed at on
1000-Hz forward will At any time after the first interval of tone ring re-ring signal Each will cause cause all timing to stop in the test line subsequent ring-forward signal the line to advance to the next state
NOTE
followed three conditions is The four-step sequence tone by loopback
line is timed or repeated until disconnect whether the test manually controlled
in distant office to make The looparound test line enables one person 2-way
This test transmission tests Test calls directed to this test line are manually originated and has two line is used to measure the near-to-far loss of 4-wire or equivalent trunks After the terminations each reached by means of separate directory numbers measuring
trunk is far- to near-end loss of all trunks in the group using 102-type test line one termination of this test line selected as reference trunk Using the reference trunk one
trunks in the other termination of the test is dialed Taking each of the remaining turn
the trunk under test and received on the line is then dialed and test power is sent over reference trunk By knowing the far- to near-end loss of the reference trunk and the overall measurement of the two trunks the near- to far-end loss is calculated by subtraction
NOTE
with callback feature This test line may be equipped security
control unit models of this unit The looparound connection is made by means of Early level allow the two circuits to be connected if tone of between 980 and 1020 Hz and
is detected one of the circuits The of signals outside greater than 15 dBm on presence disconnected In the current of this 40-Hz range causes the two circuits to be design the above are at the same frequency incoming signals within requirements regenerated line trunk for and within 0.1 dB of the received level and applied to the reference or the transmittal to the distant end The following modes of operation exist depending on type of test line equipment
are one after Two circuits are looped together when the two test appearances seized
the other
seized When the second circuit is mW tone is connected to the first circuit to be circuits connected seized the mW tone is disconnected and the are
and balance termination mW tone is provided on one test-line appearance If both are accessed the provided on the other if they are accessed individually
incoming circuits are connected
8-20 the LEC Networks 1994 SR-TSV-002275 BOC Not. on and Maintenance Issue AprIl 1994 OperatIons
circuit is combined mW-balance test line is provided on one appearance This 8.2.5.1 similar to the new 100-type test line described in the beginning of Section circuits are connected When the second appearance is seized the two incoming
before connection is In all cases where mW tone is applied 300-ms delay takes place
is returned seizure or The mW tones and made Off-hook supervision upon ring-tip on-hook intervals as balance terminations may be interrupted by 1- 2- or 3-second connection discussed under 100- and 102-type test lines Similarly the looparound may
1-second intervals for or seconds be interrupted at approximately
line and The 4ESS digital loopbacklcomplement test 606-type provides operational
for switched trunks This test line is used by digital testing capability digital 56-kbps 1A ESS-to the 1A ESS switching system for diagnostic routine and demand tests on 4ESS trunks and by the 4ESS trunk maintenance technicians for 4ESS-to-4ESS digital
with alter the received bit stream trunks digital loopback is provided circuitry to before retransmission The bit stream must be modified inverted to prevent errors due
as access in to reflections from hybrid at the 1A ESS locations Operational tests such and voice mode automatic balance transfer to digital transfer to voice or disconnect
errored are the digital tests such as bit errors block errors or seconds performed by 1A ESS maintenance circuit
technicians in both Manual tests are performed by the 4ESS trunk maintenance be in loopback and straightaway modes one-person test can performed via Circuit Maintenance loopback mode by originating data-test call System
call is 959606 After the 4ESS has set CMS to the test line The data-test assigned the technician will use test set to tests up call to the test line digital perform
to the transmit or two-person straightaway test is used to sectionalize problem will set receive direction of the digital trunk The 4ESS switching system up no
outpulse connection via CMS at the direction of the technician Communications that similar connection has are then established with the far-end technician to verify will be the two technicians been set up The appropriate digital tests performed by
8.2.5.2 Operational Test Lines
103 Test Line Signal-supervisory test line 103-type see Part of Figure 8-1 circuit for overall of provides connection to supervisory and signaling test testing with features that can be these features on intertoll trunks equipped ring-forward re-ring The features of the reached by an automatic trunk test frame or by dialing manually
103-type connection are as follows
4ESS is trademark of ATT
into one ax each end of the circuit or by one person testing Straightaway tests are made by two people
test circuit at the distant end
8-21 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Operations and Maintenance
On seizure the test trunk returns an off-hook signal
the test trunk returns an on-hook signal On receipt of ring-forward re-ring signal
120- second signal the test trunk returns On receipt of ring-forward re-ring
Interruptions-Per-Minute 1PM flash
for offices in connection with crossbar Synchronous test lines are required usually features are in the trunk relay offices where ringing tripping and supervisory incoming and functions are provided Tests equipment Marginal tests of the supervisory tripping manual or automatic basis see Part of Figure 8-1 In may be originated on either test-line operation is provided to satisfy SPC offices an equivalent program-controlled frames The test line is required to perform the requirements of the originating-office test
the functions as follows
Test for application of the ringing signal
the silent interval Test for pretripping of machine ringing during
tone for seconds followed by Provide interrupted audible ringing approximately machine 3- to 4-second silent interval On test for tripping the ringing during On certain toll some earlier test lines this sequence may be repeated once of test tone is instead of the versions single 2-second interval progress applied
interrupted audible ringing tone
Provide the following supervisory tests
1.3-second duration for synchronizing An off-hook signal of approximately offices is returned with automatic progression test equipment in originating
soak current is to supervisory relays During the off-hook period applied
is to the Return 0.2 second of on-hook supervision release current applied
supervisory relays
soak current is to the Return 0.3 second of off-hook supervision applied
supervisory relays
to the Return 0.2 second of off-hook supervision release current is applied
supervisory relays
soak is to the Return 0.3 second of off-hook supervision current applied
supervisory relays
is to the Return 0.2 second of on-hook supervision release current applied
supervisory relays
is to the Return 1.3 seconds of off-hook supervision operate current applied
supervisory relays
condition Return 0.2 second of on-hook supervision open circuit presented
to the supervisory relays
8-22 LEC Networks 1994 SR-IS V.002275 BOC Notes on the and Maintenance Issue April 1994 OperatIons
is to the Return 0.3 second of off-hook supervision operate current applied
supervisory relays
Return 0.2 second of on-hook supervision open circuit presented to the
supervisory relays
is to the Return 0.3 second of off-hook supervision operate current applied
supervisory relays
Return continuous on-hook supervision and provide an audible signal
120 dial test Audible signal may be tick-tock at 1PM interrupted tone
progress tone or high tone
office as follows Send tone signals to the originating
0.3-second intervals for 0.2 second Send audible ringing tone for interrupted on as an indication that the trunk-circuit-tripping features operated falsely
the pretripping test
indicate The incoming trunk circuit returns the regular audible ring to occurred tripping failure
test that is not as as the nonsynchronous test line provides an operational complete Part of The synchronous test but can be performed more rapidly see Figure 8-1 electromechanical offices where nonsynchronous test is the only type required for as is marginal-type tests cannot be applied directly to the incoming trunk circuit
test tenninations for frequently the case with step-by-step systems However provided circuits as connectors in step-by-step offices application of marginal-type tests to such for incoming trunk-test lines generally meet the minimum requirements nonsynchronous terminations this In some instances connector test and are frequently used for purpose
circuits toll transmission selectors The can be used to apply marginal tests to such as
minimum requirements for nonsynchronous test line are as follows
Starts to function under control of ringing signal
for of 0.5 second to Permits audible ringing signal to be returned minimum
originating office
Causes ringing to trip
the 60-IPM signal that consists of After ringing is tripped returns line-busy with low tone each alternate 0.5-second off- and on-hook signals applied during
off-hook period until disconnection
offices for of The nonsynchronous test line used in many step-by-step application as follows marginal tests to connector circuits operates
Starts to function under control of the ringing signal
for to 1.5 seconds Permits audible ringing signal to be returned
which time Returns an initial off-hook signal of 1- to 1.5-second duration during
ringing is tripped
8-23 SR-TSV002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Operations and Maintenance
after the initial off-hook Provides the following supervisory signals sequentially
tests are applied
0.5 second on-hook
to 1.5 seconds off-hook
0.2 second on-hook
0.3 second off-hook
Ce 0.2 second on-hook
0.3 second off-hook
0.2 second on-hook
0.3 second off-hook
2-second on-hook period to permit disconnection from the test line
Alternate 5.5-second off-hook and 2-second on-hook intervals are repeated
until disconnection takes place The first two 5.5-second intervals are and control provided to facilitate testing of the ring-forward re-ring end offices and are features provided on some operator-selected trunks to
desirable where these features are provided
8.2.6 CAROT System
demand transmission and The CAROT system performs end-to-end routine or trunks within defmed area The consists of operational tests on geographical system and minicomputer-based CAROT controller that performs mechanized administrative
control functions and an ROTL in most central offices The system seizes and places test
trunks Test calls received on trunks are calls over specified outgoing incoming In recent the ROTL terminated to 105 type test lines and/or responders more designs functions be combined in circuit test lines and responder-equipment can single functions be into circuits that Similarly the test line and responder can combined single do not contain an ROTL function Without the ROTL function 1-way outgoing trunks 8-6 shows functional cannot be accessed for testing via the CAROT system Figure
diagram of the CAROT system
The CAROT controller has the capability of
Causing seizure of trunks by the ROTL
and test to be connected to Causing test equipment for example responder lines each end of the trunks seized
on trunks Causing the test equipment to perform measurements
of Receiving and storing results measurements
contained in the database Analyzing test results and comparing with test limits
8-24 SOC Notes on the LEC Networks 1994 SR-TSV-002275 Operations and Maintenance Issue AprIl 1994
EE
.-a
I- CCC2 WQQ
II II II II it Cl
-J
Figure 8-6 The CAROT System
8-25 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue 1994 Operations and Maintenance April
schedule and trunk Reporting trouble indications and compiling statistics on test
performance
the network Access is The ROTLs provide the means for remote access of trunks over with the of provided to all outgoing and 2-way trunks in an office exception operator
desired for test call to trunks Access is provided to idle trunks and if particular maintenance-busied trunks in SPC offices
The ROTLs associated with SPC switches and other specially equipped ROTLs can control unit at control the maintenance state of trunks under the direction of ROTh and maintenance- manual-test position Idle trunks may be made maintenance-busy of the of either busied trunks may be restored to service verification completion action is returned to the test positions
means of an Remote manual access to and testing from an ROTL are provided by
control unit at test This allows interrogator or responderfROTL position communications technicians to conduct the same transmission tests that are conducted on demand basis an automatic basis that is calls to 100- 102- and 105-type test lines on
functions Conventional ROTLs including expanded ROTLs and small ROTLs have
Mini-ROTLs are units separate from test lines and responders single-microprocessor of the conventional test line and 52A that incorporate the functions ROTh 105-type units that the responder Mini-responders are microprocessor-controlled incorporate The conducts functions of the 105-type test line and 52A responder CAROT system
far-end test line routine automatic testing by commanding near-end ROTL to access lines over the trunk to be tested For transmission testing 100- 102- and 105-type test from electromechanical 103 synchronous and are called for operational testing ROThs
nonsynchronous types are used
CAROT can be illustrated with the case of The basic sequence of operation of the system via switched the conventional ROTL The CAROT controller has access to an ROTh
direction of the controller ROTL seizes dial-up connections Under the CAROT When trunk and sets test call to test line with directory number particular up given The controller the far-end connection is set up the ROTL seizes the near-end responder Test then commands the ROTL responder and far-end responder to perform tests signals
results to the controller The ROTL is are exchanged and measured and the are reported then commanded to release the trunk and responder
shown in 8-6 are The three basic CAROT end office test-equipment arrangements Figure
office is with illustrated in more functional detail in Figure 8-7 Central equipped
and test line that conventional ROTL with separate responder 105-type an arrangement
office is used as can be used with most types of switching systems When central to the near end the CAROT controller dials up the ROTL which connects responder then connects the with the outgoing through the access circuit The ROTL responder central office is used as far trunk to be tested and measurements are made When trunk the distant end the 105-type test line is dialed up on an incoming by originating The line be until it access to the responder end The 105-type test can parked on gains
8-26 BOC Notes the L.EC Networks 1994 SR-TSV-002275 on and Maintenance Issue April 1994 Operations
1-00100
1- II
I-0
I- CC
2.E.E 0D
O.E
II II II
LU LU
U-
Common Functions of Figure 8-7 Near-End Far-End and CAROT Testing of Test Equipment within an End Office for Three Types Equipment
8-27 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Issue April 1994 Operations and Maintenance
under the direction responder is then connected to the incoming trunk and testing begins
is the to both near- and of the originating end The responder only equipment common far-end testing functions
of both and far-end Central office equipped with mini-ROTL is also capable near- mini-ROTL the combined functions of the CAROT testing In this case the performs the conventional ROTL 105-type test line and responder except for performing and terminal-balance measurement Mini-ROTLs are typically used in end offices are
to be made from other equipped to provide termination enabling balance measurements end offices
test mini- Central office is equipped with combined 105-type line/responder
function far-end test responder Since there is no ROTL central office can only as also can termination Central offices that contain test lines separate from the responder fulfill only the far-end function
for switched trunk CAROT is the primary resource currently in use message also maintenance In addition to the analog trunk testing functions CABOT provides orders tested to turn and if record of trunk orders due and past due Trunk are prior up all tests pass are placed in the routine testing database
to CAROT has two databases One provides the routine testing information required This routine database has schedule and test all of the trunks for specified area testing
The other database is the Circuit Order Test capacity of about 100000 trunks CAROT the to circuit and Completion COTC database The COTC provides means pre-test circuit order orders and also provides reports on activity TIRKS The CABOT databases are maintained either by manual input from the system
or through direct input via CAROTffIRXS interface
It has served as the CAROT is mature system dating from the mid-seventies primary since analog trunk testing system for the BOCs deployment
active in fully digital The disposition of CAROT as an testing operations system
network environment is the BOCs long-term focal point
8.2.7 Remote Trunk Test Unit/Central Trunk Test Unit
enables communications Central Trunk Test Unit CTTU located in control center with technician to seize and test trunks originating at switching system equipped of RTIU is used with most SPC RTTU or equivalent remote test equipment The types offices with electromechanical and switching systems in exchange offices In exchange mini-ROTL and mini-RTTU combination provides the certain SPC switching systems
TIRKS is registered trademark of Beilcore
8-28 LEC Network SR-IS V-002275 BOC Notes on the 1994 and Maintenance Issue AprIl 1994 Operations
in such RTI1J functions The RITU provides an interface to the switching system way commands and test that the communications technician uses only one uniform set of
of in which the trunk The procedures regardless of the type switching system originates and also interface to the CTFU can control the RTTU over dial-up data link can The C1TU is an CAROT system to provide demand-test capability inteffigent receive and store bulk data from the CAROT terminal with storage device that can
system or other support systems
The RITU will provide the capability to do the following
Make multimeter measurements voltage resistance and capacitance on trunks to
which direct metallic access can be established
levels tone at or 16 dBm Send tones at specified frequencies and power 1004-Hz and 404- and 2804-Hz tones at 16 dBm
Measure continuously two updates per second received tones C-message noise
noise with tone and return loss
Control the maintenance state of trunks and service circuits
of circuits force near-end on- and Control the outgoing signaling state for example
off-hook states of trunk and also sense the state of incoming supervision
calls the number of another R1TU Originate outgoing test by outpulsing directory office 100- 102- or 105-type test line or manual test position in the far-end central
line manual test Terminate incoming calls as if it were 105-type test or position
between the RTTU end of the trunk under test and the Set up talk-and-listen path CTTUintheSCC
circuits Perform multimeter and voiceband transmission tests on line-terminated
where access is available
and cutoff release Perform miscellaneous line tests such as coin-ringing ringing
8.3 Common Channel Signaling
to understand the differences in circuit- For maintenance purposes it is important and Common Channel Signaling associated signaling per-trunk signaling CCS
the With circuit-associated signaling all signaling information is carried on same Since voice and share the same path it is facility as the voice path signaling of time when no voice transmission is necessary to limit signaling to periods to the time to occurring In general this limits signaling setup prior called-party connections be answer Circuit-associated signaling also dictates that multilink established before established one link at time Each succeeding link must be
office This increases the total call setup time signaling to the next can begin
8-29 SR.TSV-002275 BOC Notes on the LEC Networks 1994 Issue AprIl 1994 Operations and Maintenance
carried facilities over different With CCS the voice and signaling are on separate routes
and The voice channels are dedicated for voice voice-band data information-type
signals only tones announcements etc
channels in network from the voice channels and The signaling are separate and carry the control address supervisory signals
voice channels The signaling network is common to many
8.3.1 CCS Maintenance Plan
is to that service The suggested maintenance philosophy of the CCS network ensure
minimal and that service is restored as as possible interruptions are quickly
and the Because of the redundancy in the network architecture capacity engineering
individual link is unavailability objective for the
A/C Link unavailability 788.4 mm/yr
availability 99.850%
BID Link unavailability 1103.8 mm/yr
availability 99.789%
in the national Figure 8-8 shows this redundancy and capacity engineering signaling CCS links network Figures 8-9 through 8-15 depict the various types on
CCS maintenance can be divided into three processes
Node maintenance
Signaling link maintenance
Network maintenance
8.3.2 Node Maintenance
to detect hardware or software problems CCS node maintenance is the process designed
and quickly repair them
take to reconfigure to ensure As soon as trouble is verified the CCS node must steps indications and alert working CCS network Appropriate alarms status output messages of the trouble maintenance personnel and identify the location and the nature
8-30 SR-TSV-002275 BOC Notes on the LEC Networks 1994 and Maintenance Issue Apr11 1994 Operations
-U
ci
Figure 8-8 National Signaling Network
8-31 BOC Notes on the LEC Networks 1994 SR-TSV..002275
Operations and Maintenance issue AprIl 1994
Access Links
A-Links Database Access
scP
Legend
SCP Service Control Point
STP Signaling Transfer Point
Note Unks that connect SCPs to SIPS are also called access links
Figure 8-9 Access Links Database Access
Bridge Links
B-Links
Regional STPs
North South
North South
LATA1 LATA2
LATA1 LATA2
Note Unks that connect mated STPs to other mated STPs at the same hierarchical level LSTP to LSTP or RSTP to RSTP are
called bridge links
Bridge Unks are deployed In quad arrangement for three-way
path diversity Each link set can have maximum of eight links
Figure 8-10 Bridge Links
8-32 SR-TSV-002275 BOC Notes on the LEC NetworksI 994 Maintenance issue April 1994 Operations and
Cross Link
C-Links
Regional STP5 North NA
North NB
Local STP5
LATA1 LATA2
LATA1 LATA2
Legend
SW Signaling Transfer Point
Note Links that connect-mated STPs together are called cross links
Cross links are deployed for additional path diversity and for
passing network-management messages between mated STP5
C-link sizing Is dependent on Mink deployment There can be up to 16 lInks In single link set
Figure 8-1 Cross Links Regional STPs
Cress Unks
C-Links
Legend
STP Signaling Transfer Point
Note This symbol refers to mated SW pairs that are separated for Cross links geographically reliability are not shown but are Implied
Figure 8-12 Cross Links
33 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Operations and Maintenance AprIl
Diagonal Links D-Unks Regional STP5 RSTP
Local STPs LSTP
LATA1 LATA2 Pair Pair
Legend
SIP Signaling Transfer Point
Note Links that connect STPs of different hierarchical levels LSTPs to RSTPs are called diagonal links
for Diagonal links are deployed in quad arrangement three-way path of links diversity The link set Is sized at maximum eight
Figure 8-13 Diagonal Links
Fully Associated Links
F-links
Legend SCP SeMce Control Point SSP Service SwitchIng Point
STP Signaling Transfer Point
CCSSO Common Channel Signaling Switching Office
Note Links that connect CCSSOs and/or SSPs direcy together that is not
via SIPS are called fully associated links
These links could be deployed In community of interest where no SIPs would be available for bunk signaling CLAS services The maximum link-set size is 16
CLASS Is service mark of Belicore Links Figure 8-14 Fully Associated
8-34 SR-IS V-002275 BOC Notes on the LEC Networks 1994 and Maintenance Issue AprIl 1994 Operations
Summary
Signaling Date Links Summary
RSTP$ A-Unk
LSTPs
A-Unk
A-Unk
Legend
sCP SeMce Control Point
sSP Service Switching Point SIP Signaling Transfer Point
CCSSo Common Channel Signaling Switching Office
Note The above visual depicts two-level CCS network architecture that includes summary of possible link deployment Extended links E-Unks are utilized to Interconnect an SSP to non-mated pair of STPs
Figure 8-15 Signaling Data Links Summary
8-35 BOC Notes on the LEC Networks 1994 SR-TSV-002275 issue 1994 Operations and Maintenance AprIl
five The node-maintenance strategy includes tests
Continuous automatic tests
Per-operation or per-message automatic tests
Periodic automatic tests
Semiautomatic tests
Manual routine tests
8.3.3 Signaling Link Maintenance
signaling link has three major components transmission link and two signaling-link terminals
network such the Transfer Point The SS7 protocol allows the CCS elements as Signaling STP Service Switching Point SSP or Service Control Point SCP to perform link monitoring automatic link turndown and trouble sectionalization There are four trouble detection routines
Signaling unit error-rate monitor
Acknowledgment time-out indicator
Unexpected backward sequence number received
Unexpected forward indicator bits
8.3.4 CCS Interface
The CCS node should be able to provide either of the following physical-level interfaces
CC1T recommendation V.35 describes 34-pin connector that connects the terminal
equipment to the transmission link The transmission link provides Data Service Unit DSU Channel Service Unit CSU and Office Channel Unit OCU functions
The DSOA interface is 4-wire interface that connects the signaling terminal
equipment to the transmission link The signaling terminal equipment provides the
necessary DSU CSU and OCU functions
8.3.5 Present Link Testing Strategy
There are various strategies for link testing
Figure 8-16 shows CCS test access via Switched Maintenance Access
System/Switched Access Remote Test Systems SMAS/SARTS typical A-Link
56-kbps circuit This is the present link-testing strategy The figure shows the
SMAS/SARTS with wired-in-access for loopback testing
8-36 SR-TSV-002275 BOC Notes on the LEC Networks 1994 and Maintenance issue AprIl 1994 OperatIons
Cross-Connect Figure 8-17 shows digital test access via the Digital System DCS
This is also present strategy
Figure 8-18 shows the DSOA link testing arrangement which provides an opportunity of links used in the network series of for in-depth maintenance testing the CCS the network elements At the data port-type channel units DSO-DP connects CCS
SSP the V.35 interface is used
8.3.6 LInk CircuIt Parameters
of the and link Test requirements for provisioning and maintenance digital and data service units The test circuits include link circuits using data port 500-type
requirements are listed in the table below
Table 8-2 Test Requirements for and Digital Link Circuits
Link Channel Loopback Error 10 Mm
10 Link Straightaway End-to-End Error
with data service units channel or end-to-end Circuits using data port require loopback The tests using KS-20909 transmitter and KS-20908 receiver or equivalent
requirement is for errors in 10 minutes
8.3.7 Data ServIce Unit Test
Tests performed from the V.35 interface of the DSU at one end of the link and the test
DSU at the other end should be within the values listed below in Table 8-3
Table 8-3 Data Service Unit Test
Link Local test LL error 10 miii
Link DSU functional test Error 10 mm
Link Straightaway digital test Maximum bit errors in
15 mm in both directions
Link Loopback to distant end Maximum bit errors in
15 mm
8-37 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Operations and Maintenance April
V.35 T-Une V.35
500 A-Type 500 A-Type Data-Service Data-Service Unit Unit
Legend
DSOA Digital Signal Zero 0CUDP Office Channel Unit Data Port SARTS Switched Access Remote Test Systems SMAS Switched Maintenance Access System
SSP Service Switching Point
STP Signaling Transfer Point
ATT-manufactured systems used to access and test special seMce circuits from remote location
Figure 8-16 CCS Test Access via SMAS/SARTS
8-38 SR-TSV-002275 BOC Notes on the LEC Networks 1994 and Maintenance Issue April 1994 Operations
interface Digital V.35 Channel Bank
500 A-Type Data-Service Unit
Legend
Cross-Connect DCS Digital System
DSOA Digital Signal Zero
MDF Main Distributing Frame OCUDP Office Channel Unit Data Port sARTS Switched Access Remote Test Systems SMAS Switched Maintenance Access System
SSP Service Switching Point
STP Signaling Transfer Point
ATT-manufactured systems used to access and test special service circuits from remote iocation
Figure 8-17 Test Access via Digital Cross-Connect System
8-39 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 Operations and Maintenance Apr11
STP Office Intermediate Office SSP Office
Legend Zero DSOA Digital Signal DSU Data Service Unit Ocu Office Channel Unit sSP Service Swttching Point sip Signaling Transfer Point
Une Loopback Drop Loopback
Figure 8-18 DSOA Link Testing Arrangement
8-40 1994 SR-TSV-002275 BOC Notes on the LEC Networks and Maintenance Issue April 1994 OperatIons
8.3.8 Network Maintenance
Failures and overloads in the CCS network are detected by the software or through the receipt of Signaling System SS7 messages
local and remote The following real-time network problems are reported to the maintenance forces
Start or end of signaling link congestion
Start or end of signaling link overflow
Near-end manual changeover or changeback
Signaling link declared failure
Far-end processor outage
Node isolation
8.3.9 Link Maintenance Flow
The flowchart in Figure 8-19 shows the usual sequence of maintenance activities that
occur in the event of link failure
8.4 Switch Diagnostics
to conduct routine automatic tests and to SPC switching systems are designed operational analyze trunk faults In addition per-call tests are made Application of these programs certain the can result in error messages indicating possible trunk troubles In cases take out of service switching system wifi automatically equipment
Automatic progression testing is the primary mode of routine testing Under program with trunk-network control the diagnostic is performed on trunks and other equipment various standard appearances Depending on the type of trunk and its operational record
tests are initiated Trunks are not necessarily tested daily
basis for each An automatic continuity and polarity test is run daily or on scheduled the and outgoing trunk This test is to check that the correct voltages appear on tip ring office of the trunk The test does not require placing call to distant
trunk-maintenance list Trunks that fail either routine tests or per-call tests are placed on
Trunks that do tests at this be for further testing and analysis not pass point may removed from service depending on the number of trunks already out of service
The results of tests conducted by the switch are transmitted to the appropriate work
undertake tests center that is SCC or TOSC The work center may then more thorough
of the trunk
8-41 BOC Notes on the LEC Networks 1994 SR.TSV-002275 Operations and Maintenance Issu April 1994
Legend
MMOC Minicomputer Maintenance and Operations Center
NTEC Network Technical Enginoering Center NTF No Trouble Found
scc Switching Conol Center ssc Special Services Center
Figure 8-19 Example of Link Maintenance Flow
8-42 SR-TSV-002275 BOC Notes on the LEC Networks 1994 Maintenance issue April 1994 Operations and
In exchange offices with electromechanical switching systems similar testing functions may be performed by the machine under the control of paper-tape reader Test results are punched out on cards at the central office by the switch In electromechanical offices transmitted central equipped with an automatic trunk-analysis system test results are to data processor The central processor performs analysis generates trouble reports and transmitted data links gives summaries of central office activity This information is over to workstations at SCCs
In offices with electromechanical switching systems equipped with an expanded ROTL of or mini-ROTL automatic operational tests can be conducted under control the
is installed These advanced CAROT system if the appropriate optional equipment operational trunk tests provide all the operational testing capabilities that are provided by of trunks in end offices and in automatic progression tests except for certain types Common-Control Switching Arrangement CCSA offices
8.4.1 Digital Systems
Digital switching systems are capable of analyzing and reporting slips Bipolar Violations BPVs and OOF conditions as an aid to network maintenance These the interface methods are dependable where the facility is entirely at the same bit rate as
machine of the is to another bit rate to the switching Where any part facility multiplexed or is provided with automatic protection switching the facility cannot be effectively monitored for BPVs because they are removed by the multiplexers and automatic protection switches
The digital switch provides surveillance and performance-monitoring capabilities not available in the analog switching world
Administrative procedures associated with switch maintenance must include an analysis of the parameters that may indicate network degradation Each digital switch surveillance manufacturer provides specific set of network performance-monitoring or capabilities These capabilities have several basic functions in common
To indicate the failure of an interfacing Ti system by reporting CGA The CGA is
activated when preset parameter for Bit Error Ratio BER is exceeded The BER is
derived by the switch from the count of BPVs received on the incoming Digital
Signal level DS 1.544 Mbps bit stream
To automatically remove from service the trunks associated with Ti system with when the reaches reported CGA and to return those trunks to service BER preset
acceptable parameter
To provide report of timing errors on the interfacing digital network by counting the
number of slips received in 24-hour period and reporting when that count exceeds
the set parameters
frame with the To provide report when the switch is unable to maintain alignment
incoming bit stream OOF and unable to reframe for specific period of time
8-43 BOC Notes on the LEC Networks 1994 SR-TSV-002275 Issue 1994 OperatIons and Maintenance April
8.4.2 DigItal Switch Alarms
alarms and related data Table 8-4 lists the various types of digital switch
Table 8-4 Digital Switch Pdarms
Parameter Threshold Time Window Alarm
Loss of Signal Red Condition 2.5 seconds Major CGA
BER 1OLow Few minutes to hour Minor
103High Few seconds Major CGA
OOF Count 17Low 24 Minor
511 High 24h Major
Slip Count Low 24 Minor
255 High 24 Major
It is important to be aware that the BER parameter is based on
count of BPVs received at the switch As discussed elsewhere
in this document multiplexing on the network removes the BPVs
thus negating the switchs capability to detect trouble via
this parameter
8.4.3 Network Synchronization
network Digital network synchronization is vital resource for the switched trunking network The Digital network maintenance should begin with properly synchronized of switch manufacturers in the proliferation of digital PBXs and the different varieties network have highlighted this important requirement Synchronization problems will cause slips on the network
data slip is defined as the deletion or repetition of one frame of DS1 1.544 Mbps 193 bits due to frequency differences between the transmit and receive clocks of
the effects are as transmission path Some of of slips on voice and data transmission follows
Audible clicks on the line for voice transmission Clicking noise increases as the slip
rate increases
8-44 SR-TSV-002275 BOC Notes on the LEC Networks 1994 and Maintenance issue Apfli 1994 Operations
the Signal errors loss of frame and loss of data for voiceband data Depending on the transmission data be rate of slips and error correction capability of media may
resent
Errors loss of data and an increase in throughput time due to resends
be and should be The significance of network synchronization cannot overemphasized primary concern in any network maintenance plan Each BOC has synchronization resolve indications that be or coordinator assigned to investigate and slip may persistent otherwise unresolved
8.4.4 Eli ESS Switch Equipped with Digital Carrier Terminal
The 1EJ1A ESS switch equipped with DCT interface frames provides maintenance features that continually monitor the performance of the DS bit stream The DCT
to the maintenance The reports error rates that exceed preset parameters ESS position
DCT can detect BER OOF and incothing signal synchronization problems slips
NOTE
Slips are detected in the 1A ESS switch only if it is equipped with the feature Circuit Switched Digital Capability CSDC
The 1EI1A ESS DCT performance monitoring capabilities are not as well known or used as those of the digital switches but they indicate the same problems on the network The output messages in the lE/1A ESS switch that indicate the digital errors listed above are as follows
FMO3 DCT message reports that the BER threshold was exceeded
FMO4 DCT message reports that the low OOF threshold has been reached
FM1 DCT message contains the 24-hour slip count in 1A ESS switches equipped with CSDC
be filtered the The FMO3 and FMO4 output messages can by Switching Control Center
System SCCS and displayed for analysis purposes The 1EJ1A ESS output manual contains specifics relating to these messages
The 1ElA ESS switch also initiates CGA on DS1 failure to remove the affected thinks from service
8.4.5 AutomatIc Operational Trunk Testing
Both the analog SPC switch and the digital switch have the capability to run programmed automatic operational tests on trunks These tests are usually run at night and perform continuity and signaling tests Trunks that fail are taken out of service and reported on
Trunk Out-of-Service list for maintenance
85