NOTES ON DISTANCE DIALING AMERICAN TELEPHONE AND TELEGRAPH COMPANY ENGINEERING DEPARTMENT SYSTEMS PLANNING SECTION (COPYRIGHT, ]968, BY AMERICAN TELEPHONE AND TELEGRAPH COMPANY) PRINTED IN U.S.A. NOTES ON DISTANCE DIALING TABLE OF CONTENTS FOREWORD SECTION 1 GENERAL PAGE INTRODUCTION .......................... 1 DESCRIPTION OF SECTIONS ..................... 2 oNUMBERING PLAN - SECTION 2 ................. 2 ¯ SWITCHING PLAN - SECTION 3 .................. 3 o SIGNALING- SECTION 4 ...... 3 ¯ EQUIPMENT REQUIREMENT- SECTION 5 ............. 3 ¯ TRANSMISSION CONSIDERATIONS - SECTION 6 .......... 4 oMAINTENANCE CONSIDERATION- SECTION 7 ........... 4 oINTERNATIONAL DIALING - SECTION 8 ............. 5 ° NEW SERVICES - SECTION 9 .................... 5 ¯ BIBLIOGRAPHY- SECTION 10 ...... ’ ..... ....... 5 FUNDAMENTAL PLANS ...................... 5 SECTION 2 NUMBERING PLAN GENERAL NUMBERING PLAN AREA (NPA) CODES ............... 2 CENTRAL OFFICE CODES DIALING PROCEDURES FOR CUSTOMER DISTANCE DIALING ........ 4 CONVERSION OF EXISTING NUMBERING PLANS TO 7-DIGIT FORM ..... 7 RELATION OF CENTRAL OFFICE CODES TO CENTRAL OFFICE EQUIPMENT . 8 TOLL CENTER AND OPERATOR CODES NUMBERING OF COIN STATIONS CENTRAL OFFICE NAMES ...................... 10 NUMBERING FOR AN OFFICE SERVING CUSTOMERS IN TWO NUMBERING PLAN AREAS ......................... I0 NUMBERING FOR OFFICES SITUATED IN ADJACENT NUMBERING PLAN AREAS WITH EXTENDED AREA SERVICE BETWEEN THEM ...... I0 Charts: 1. Numbering Plan for Distance Dialing 2. Numbering Plan Areas With Codes 3. Numbering for an Office Serving Customers in Two Numbering Plan Areas APPENDIX A- NUMBERING PLAN AREAS WITH CODES SECTION 3 SWITCHING PLAN GENERAL ...................... ...... 1 DEFINITIONS .......................... 2 HOMING ARRANGEMENTS AND THE INTERCONNECTING NETWORK .... 4 SELECTION OF CONTROL SWITCHING POINTS ............. 5 EFFECTS ON PLANT LAYOUT .................... 6 DESTINATION CODE ROUTING .................. " . 6 Charts: 1. Switching Plan (Basic Principle) 2. Basic Requirements for Control Switching Points (CSP’s) 3. Effect of Establishing a CSP APPENDIX A- ALTERNATE ROUTING (WITH CHARTS A1 AND A2) APPENDIX B- ROUTING PATTERNS UNDER THE SWITCHING PLAN (WITH CHARTS B1 AND B2) SECTION 4 SIGNALING GENERAL ON-HOOK AND OFF-HOOK SIGNALS ........... ~ . 3 DC SIGNALING SYSTEMS ....................... 12 AC SIGNALING SYSTEMS ...................... 20 AUDIBLE TONE SIGNALS ...................... 29 OTHER SIGNALS ......................... 32 SENDER AND REGISTER TIMING AND EFFECT ON SIGNALING ....... 35 Charts: 1. Signals Required in Distance Dialing 2. Tones and Announcements Recommended for Distance Dialing 3. Use of Signals With Direct Distance Dialed Calls 4. Delay Dialing Method A and Wink Start Pulsing 5. Delay Dialing Method B - Sender Connected After Delay Dialing Signal 6. Delay Dialing Method B - Sender Connected Before Delay Dialing Signal 7. Digit Timing Requirements 8. Sender, Register, or Link Attachment Timing Requirements SECTION 5 EQUIPMENT REQUIREMENTS GENERAL ............................ ° 1 STATION EQUIPMENT ....................... 2 DIAL SWITCHING EQUIPMENT ..................... 5 MISCELLANEOUS CENTRAL OFFICE AND TRAFFIC ADMINISTRATION FACILITIES .......................... 16 Charts : 1. Typical Station Number Cards 2. Typical Rotary and Pushbutton Dial Telephone Sets 3. Typical Multibutton Telephone Sets 4. Minimum Number of Digits Central Office Equipment Should Be Arranged to Receive from the Distance Dialing Network 5. Stop Dial S~gnals- A Typical Application 6. Traffic Separations Available With No. 4 Type and Crossbar Tandem Systems 7. Tone Appliers 8. Digit Capacities of Various Switching Systems 9. Outpulsing Capabilities of Switching System Senders 10. Data Required for Recording Billed Messages APPENDIX A-TYPICAL TRUNKING DIAGRAMS FOR STEP-BY-STEP OFFICES (WITH CHARTS A1, A2, AND A3) SECTION 6 TRANSMISSION CONSIDERATIONS GENERAL TOLL SWITCHING PLAN ...................... 2 VIA NET LOSS CONCEPTS ............ .......... 4 ¯ DESIGN FACTORS ................... .... 4 ECHO TOLERANCE TO ECHO .................... 5 SINGING NOISE AND CROSSTALK .................... 7 ¯ VIA NET LOSS DESIGN PLAN .............. : . 7 OVERALL CONNECTION LOSS REQUIREMENT .......... 8 VIA NET LOSS AND VIA NET LOSS FACTORS . .......... 11 APPLICATION OF ECHO SUPPRESSORS ............. 12 TRUNK LOSS OBJECTIVES ...................... 13 ¯ EXPECTED MEASURED LOSS (EML) ................ 13 ¯ INSERTED CONNECTION LOSS (ICL) .............. 14 ¯ INSERTED CONNECTION LOSS (ICL) OBJECTIVES .......... 14 INTERTOLL TRUNKS .................... 14 SECONDARY INTERTOLL TRUNKS ........ ....... 16 TOLL CONNECTING TRUNKS ............... 16 END OFFICE TOLL TRUNK (DIRECT-LONG-HAUL) ........ 17 THROUGH BALANCE AT 2-WIRE CSP’s ................. 17 TERMINAL BALANCE AND TOLL CONNECTING TRUNK DESIGN . .... ¯ 20 oTERMINAL BALANCE OBJECTIVES ................ 20 ~ oTERMINAL RETURN LOSSES ........... i ¯ ...... 21 ECHO FREQUENCY IMPROVEMENT ...... ~ ........ 21 SINGING FREQUENCY IMPROVEMENT ............. 22 oTOLL CONNECTING TRUNK DESIGN ................. 22 IMPEDANCE COMPENSATION ................. 24 FIXED 2 dB PADS ...................... 25 DROP BUILDING OUT .................... 25 MATCHING OFFICE IMPEDANCES ............... 26 ¯ SWITCHBOARD OPERATOR’S TELEPHONE SET ........... 26 ¯ SUMMAI~Y OF EQUIPMENT REQUIREMENTS ...... : ...... 27 CUSTOMER LOOP PLANT DESIGN ................... 27 MAINTENANCE CONSIDERATIONS .................. 28 ¯ TRUNKS ¯ TYPES OF TRANSMISSION MEASUREMENTS ............ 29 ® TEST EQUIPMENT AND TEST POWER SOURCES ........... 30 ¯ ACCESS TO TRUNKS FOR TRANSMISSIDN MAINTENANCE PURPOSES . 30 ¯ EVALUATION OF THE RESULTS OF TRANSMISSION MAINTENANCE 31 ¯ CORRECTION OF TRANSMISSION TROUBLES ............. 33 ¯ THROUGH AND TERMINAL BALANCE ............... 33 ¯ LOOP PLANT MAINTENANCE ................... 34 Charts: 1. Trunk Losses WithVia Net Loss (VNL) Design 2. Echo Paths 3. Talker Echo Tolerance for the Average Observer 4. Relationship Between Overall Connection Loss (Class 5 to Class 5 Office) and Echo Path Delay 5. Typical Connections of Two Intermediate (Intertoll) Trunks at a 2-Wire Switching Office. 6. Impedance Compensator- 837A Networks 7. Impedance Compensator- 837B Networks 8. Impedance Compensator (SD-95756) 9. Fixed 2 dB Pad Arrangements SECTION 7 MAINTENANCE REQUIREMENTS GENERAL MAINTENANCE FACILITIES ...................... 2 Chart: 1. Test and Maintenance Facilities by Class of Office APPENDIX A-DESCRIPTION OF TEST LINES SECTION 8 INTERNATIONAL DIALING GENERAL WORLD NUMBERING PLAN ..................... INTERNATIONAL ROUTING PLAN .................. SPECIAL FACILITIES (TASI) .................... 7 SIGNALING ........................... 7 TRANSMISSION AND MAINTENANCE ................. 8 TRAFFIC OPERATING ....................... 9 Charts : 1. World Numbering Zones and World Major Switching Offices 2. International Routing Plan (Classification and Arrangement of Centers) SECTION 9 NEW SERVICES UTILIZING DDD NETWORK GENERAL ............................ 1 WIDE AREA TELEPHONE SERVICE (WATS) - GENERAL ......... 1 OUTWARD WATS ......................... 1 INWARD WATS .......................... 2 TELETYPEWRITER EXCHANGE (TWX) SERVICE ............ 3 DATA SERVICES ......................... 4 Charts: 1. Inward WATS Switching Plan 2. TWX- Special Area Codes SECTION 10 BIBLIOGRAPHY GENERAL ............................ 1 LIST OF REFERENCES AND RELATED SUBJECTS .. ........... 1 ¯ GENERAL AND HISTORICAL ................... 1 ¯ SWITCHING .......................... 3 ¯ TRANSMISSION ........................ 5 ¯ SIGNALING .......................... 9 NOTES ON DISTANCE DIALING FOREWORD These Notes outline technical requirements and fundamental principles of operator and direct (customer) distance dialing. They are a revised edition of "Notes on Distance Dialing - 1961," which superseded the earlier "Notes on Distance Dialing- 1956." This issue of the Notes includes two sections not in previous issues. Section 8 discusses International Dialing and Section 9 covers in general some of the new services that are now being routed on the message network. The remaining sections have been generally updated and revised. The Notes are confined to matters bearing directly on distance dialing. In addition to tech- nical data required by manufacturing and engineering personnel, discussions are included cover- ing in some detail the Numbering Plan, the Switching Plan, Equipment, Transmission and Maintenance Considerations, etc., which should be of value to operating and maintenance people. For those interested in the overall plan rather than technical details, the "General" section briefly outlines the contents and scope of the other sections in non:technical terms, and discusses some of the fundamentals that are considered when preparing to incorporate offices into the distance dialing network. In many instances it has been necessary to specify certain requirements or design objec- tives without including a discussion of the factors underlying their selection. Also, there are many problems in the Accounting, Commercial, Public Relations and Traffic fields as well as Engineer- ing that relate to distance dialing but are not covered by these Notes. Nevertheless, the Notes do furnish much of the information needed by the telephone industry for t.he successful coordina- .tion of efforts between manufacturing and Operating Companies in furthering distance dialing. While the Notes describe requirements as visualized today, details will necessarily change as further