Field Engineering Education Student Self-Study Course IBM Confidential Field Engineering Education Student Self-Study Course IBM CDnfidential This document contains information of a proprietary nature. ALL INFORMATION CONTAINED HEREIN SHALL BE KEPT IN CONFI­ DENCE. None of this information shall be divulged to persons other than: IBM employees authorized by the nature of their duties to receive such information or individuals or organizations authorized by the Field Engineering Division in accordance with existing policy regarding release of company information. Common Carrier Facilities for Teleprocessing PREFACE This course is provided to acquaint Customer Engi­ neers with some of the important concepts of Com­ mon Carrier equipment and facilities as used in Teleprocessing environment. This course will also provide the Customer Engineer with a permanent reference for these facilities. Address comments concerning the contents of this publication to: IBM Corporation, Field Engineering Education, Dept. 911, Poughkeepsie, N. Y., 12602 Printed March 1966 IBM CONFIDENTIAL CONTENTS SECTION 1. TELEGRAPH SESSION 3, LONG DISTANCE SYSTEMS • 39 Review Questions 40 SESSION 1, TELEGRAPH SYSTEMS 5 Telegraph Principles 6 SESSION 4, CHANNEL FACILITIES. 41 Transmission Methods • 6 Channels Necessary • 41 Functional Units 6 Grades of Channels • 41 Polar Relays 6 Review Questions 43 Junction Boxes 6 Line Arrestor (Heat) Coils 9 SESSION 5, CIRCUIT CHARACTERISTICS • 45 Repeaters 9 Review Questions 47 Representative Type Equipment 11 Basic Telegraph Circuit 13 SESSION 6, LINE EQUIPMENT 49 Telegraph Signal Distortion • 15 Review Questions 53 Review Questions 18 SESSION 7, DATA TRANSMISSION 55 SESSION 2, TELEGRAPH SWITCHING SYSTEMS 19 Review Questions 56 Types of Switching Systems • 19 AT&T Fully Automatic Teletypewriter System 81Dl 19 SESSION 8, INTERFACING DATA TERMINALS AND AT&T Selective Call System 83B2 • 19 COMMUNICA TION FACILITIES 57 Western Union Plan 11SA 20 General Requirements • 57 83B2 Message Format • 20 Review of Basic Data Set • 57 Addressing Format • 20 Recommended Standard 232A of EIA • 58 Polling Format 20 Line of Demarcation 58 Special Functional Units • 21 V oltage Levels and Circuits • 58 Stunt Box • 21 Other Specifications 60 Function Genera tor • 24 Review Questions 60 Review Questions 25 SESSION 9, DATA SET - IBM LINE ADAPTERS 61 SESSION 3, TELEGRAPH LINE FACILITY DIAGNOSTIC • 27 General Characteristics 61 Distortion Measurement 27 Limited Distance Adapter Type 2B • 61 Line Current Check 27 Transmit Operation • 61 Transmit Unity MIS Ratio Check • 27 Receive Operation • 62 Bias Winding Adjustment • 28 Review Questions 64 Fortuitous Distortion Measurement • 28 Common Carrier Tests • 29 SESSION 10, DATA SET - WESTERN ELECTRIC TYPE 103 • 65 Review Questions 29 Transmission Frequencies • 65 Interface • 66 SECTION 2. ASYNCHRONOUS DATA COMMUNICATIONS Operational Keys 66 Applications • 67 SESSION 1, TELEPHONE SYSTEMS. 31 Channel Establishment 67 Simple Local Exchange System • 31 Manual Channel Establishment (103A 1) 68 Review of Components 32 Automatic Channel Establishment • 68 Review Questions 34 Channel Establishment for 103B Data Set. 68 Channel Establishment for 103F • 68 SESSION 2, TELEPHONE SWITCHING 35 Review Questions 69 The Manual Switchboard • 35 Automatic Switching System • 35 SESSION 11, DATA SET - WESTERN ELECTRIC TYPE 202 • 71 Telephone Dial • 35 General 71 Tone Dialing 36 Differences - A and B vs. C and D • 71 Step-by-Step Switching 36 Interface • 73 Panel Switching • 36 Channel Establishment 73 Crossbar Switching • 37 Error Expectancy 73 Electronic Switching 37 Reference Source 74 Review Questions 38 Review Questions 74 IBM CONFIDENTIAL SESSION 12, DATA SETS FOR PARALLEL DATA AND SESSION 2, DATA SETS - 300 SERIES 95 AUTO:MATIC CALLING 75 Review Questions 96 Data Set - Western Electric 400 Series (Parallel Data). 75 Western Electric 401 Series 75 Western Electric 402 and 403 Series 77 ANSWERS TO REVIEW QUES TIONS Data Set - Western Electric 801 Automatic Calling Unit SECTION 1 97 (ACU) 77 Session 1 97 Interface 77 Session 2 97 Operation Sequence 77 Session 3 97 Options 77 Review Questions 79 SECTION 2 97 SESSION 13, TESTING, DIAGNOSIS, AND Session 1 97 TROUBLESHOOTING 81 Session 2 97 Initial Information Needed 81 Session 3 97 Testing at the Interface 82 Session 4 98 Data Set Testing 82 Session 5 98 Measurement of Jitter • 83 Session 6 98 Common Carrier 900 Test Sets 83 Session 7 98 Summary and Reference 84 Session 8 98 Published Service Aids 84 Session 9 98 Review Questions 85 Session 10 99 Session 11 99 SECTION 3. SYNCHRONOUS DA TA COMMUNICATION Session 12 99 Session 13 100 SESSION 1, SYNCHRONOUS FACILITIES 87 Digital Interface 87 SECTION 3 100 Data Set, Western Electric Type 202 87 Session 1 100 Data Sets, Four-Phase • 88 Session 2 101 Data Set, Western Electric Type 201 • 89 Interface 91 Options 92 Review Questions 93 BIBLIOGRAPHY • 102 IBM CONFIDENTIAL SECTION 1 TELEGRAPH SESSION 1 TELEGRAPH SYSTEMS Upon completing this session, you should be able to explain the principles, func­ tional units, and telegraphic circuits used within telegraph networks. You will also become familiar with distortion in telegraph circuits and how distortion is handled. Highlights: • Principles Concepts Speeds o Transmission Methods Wire Radio Telegraph o Functional Units Polar Relays 225A IBM Mercury-Wetted WU 202 Junction Boxes 63Cl, 2 IBM Line Terminator Box Plugs Line Arrestor Coils Repeaters Regenerative (mechanical) Regenerative (electronic) o Representative Type Equipment RO - Receive Only Page Printer KSR - Keyboard Sending and Receiving Unit ROTR - Receive Only Typing Reperforator PERF - Perforator KTR - Keyboard Typing Reperforator TD - Transmitter Distributor RT - Reperforator Transmitter ASR - Automatic Sending and Receiving Unit • Basic Telegraph Circuit Circuit Tapes Line Currents Line Voltages • Telegraph Signal Distortion IBM CONFIDENTIAL 5 TELEGRAPH PRINCIPLES 45 cps are common. A modification of this method is the introduction of a coaxial line instead of the Telegraph circuits have line speeds ranging from radio link (Figure 1-4) approximately 45 to 75 BPS, and normally are at­ Radio telegraphic utilizing audio FSK (Figure 1-5) tached to terminals employing the asynchronous is yet another method in use today. This concept mode of transmission. The major difference be­ utilizes a fixed carrier radio transmitter and relies tween telegraph transmission and all other methods on audio modulation (AFSK). The incoming tele­ is the type of modulation used. Telegraph circuits graphic data at the transmitter is converted to tones rely on direct current modulation. Direct current and is used to modulate the radio frequency ca~rier. modulation is particularly adaptable to low-speed, The receiving station converts the incoming AFSK low-quality lines. The basic telegraph circuit signal back to tones, and then to telegraphic (cur­ consists of a dc power supply, send relay points, rent - no current) data. and a receive relay coil. Refer to Figure 1-1. FUNCTIONAL UNITS I----l ,---, I I I I Polar Relays I Battery I I I Supply I I o-I-------f qq t------..IVV'-----t----J I The polar relay connects the terminal equipment L ___ J L ___ ---1 and the telegraph line. There are three basic types Send Receive Circuit Circuit of polar relays. The first, WE 225A (Figure 1-6), is manufactured by Western Electric and is used in FIGURE 1-1. BASIC TELEGRAPH CIRCmT the IBM 067 Transceiver. The 255A plugs into a special socket and is held in place by spring clips. The relay has two separate coils: the pick coil and TRANSMISSION METHODS a bias coil. The bias coil is normally energized with an adjustable dc voltage. The bias winding gen­ There are two basic methods of telegraph trans­ erates a magnetic field which either bucks or boosts mission: the action of the pick coil. The effect of the bias 1. Straight wire coil allows the characteristic pick and drop time of 2. Radio telegraph the relay to be varied. Figure 1-7 is a diagrammatic The first we will discuss is the straight wire representation of the polar relay. method (Figure 1-2). In this case, the telegraphic The second basic type of polar relay is manufac­ data to be transmitted is converted to current - no tured by IBM (Figure 1-8) . It consists of a mercury­ current and is imposed on a two-wire network. This wetted reed relay and coil. The pick coil surrounds method is primarily used at the originating and ter­ the glass reed capsule 'similarly to the standard IBM minating ends of long distance data links. reed relay. The relay is available in two versions, the first being a send relay which has one coil. The receive relay has both pick and bias coils. The IBM polar relays are mounted on a SMS card. The com­ plete SMS card must be replaced if any of the relays Telegraph Telegraph Equipment Equipment becomes defective. Another type of polar relay is the WU 202A (Figure 1-9), also used in the IBM 067 Transceiver. The armature operates on a rocker principle. It FIGURE 1-2. STRAIGHT WIRE TELEGRAPH LINE pivots in the center allowing the contacts at the ends of the armature to open and close. The relay has both pick and bias windings. The second and most versatile method of tele­ graphic transmission is through the incorporation of radio. This concept takes on many configurations, the first of which is radio telegraph FSK (Figure 1-3). This method employs a radio transmitter/receiver DANGER that is frequency-keyed by incoming telegraphic (current - no current) data. The receiving station Be careful when working near polar relays. detects the frequency shift and generates telegraphic Other than normal voltages are present. Voltage (current - no current) output. Frequency shifts of Iof 130 vdc and greater are present. 6 IBM CONFIDENTIAL 1-------1 Radio Radio Telegraph Transmitter/I--_----l Transmitter/ Telegraph Equipment Receiver L-------l Receiver Equipment 1-------1 (FS K) (FSK) FIGURE 1-3. RADIO TELEGRAPH - FSK Telegraph Telegraph Carri.er ~ ~ Carrier Coaxial Line Generating Generating Telegraph Equipment I----{:) }-- Equipment Telegraph Transmitter/ Transmitter/ Receiver J- ~ Receiver Telegraph V ~ Telegraph ,.