TABLE OF CONTENTS Page 1. INTRODUCTION. 1 General. .. 1 List of Drawings ........... , . 2 TestiQ.g Equipment. 3 2. DESCRIPTION AND FUNCTIONS OF COMPONENT UNITS. 5 Terminal Panel. 5 Line and Balancing Equipment ....... ; . 10 Repeaters. 10 Carrier Transfer Equipment. 13 3. POWER SUPPLY REQUIREMENTS. 13 TerminaL . 13 Repeater. 13 4. TRANSMISSION PERFORMANCE. 14 Transmitting and Receiving Gain. 14 Operating Levels .................. .... ....... .... .............. ~ . 16 Transmitting Signaling Power . .. 16 Carrier Supply... 16 Repeater. 17 Transmission Range of System Without Intermediate Repeater. 17 Effects of Repeaters on Transmission Range. 19 Overall System Transmission-Frequency Characteristics ....... ..................... 20 Overall System Stability. 21 Load Capacity. 22 Crosstalk and Noise ............................................................ 22 5. CHARACTERISTICS OF OPEN-WIRE LINES AND CABLES .................. 22 Attenuation . 23 Characteristic Impedance . 25 Reflection Effects . 28 Cable Loading .......... , . 28 Impedance Matching Transformers ................ , . 30 Way Station Bridging Filter ....................................... ........... 32 6. APPLICATION TO SPECIFIC CASES ......................................... 34 Attenuation of Line. 35 Effect on Voice-Frequency Telephone Circuits ... ...... .............. ........... 39 Effect on Telegraph Circuits. 40 Crosstalk and Noise ............. .... .... .. ...... ............ , ............. 41 Signaling at Terminal Offices ... .............. ........... ............. ....... 41 Selector Sets ............................................. .... ................ 41 7. INSTALLATION .......... .... .......................... ................... 43 Installing Procedure. 43 Circuit Operation Tests. 45 8. OVERALL SYSTEM LINE-UP ...................... ..................... ... 46 Terminal Transmitting Level ................... ............... .... ...... .... 47 Terminal Transmitting Signal Output Power. 49 Repeater Output Level. 49 Receiving Level. 50 Carrier Supply Synchronization ..... _. 52 Channel Net Loss Frequency Measurement ............ .... .................... 52 9. SERVICE ADJUSTMENTS .................... ............ .. .... ........... 54 Channel Net Loss Measurements ....... .... .. ...... ............ ............. 55 System Signaling Check. .. .. 55 TCI Library https://www.telephonecollectors.info/ TABLE OF CONTENTS (Cont'd.) Page 10. TROUBLE LOCATION TESTS ...................... ..... .. .. .. .. .... .. 56 A-C Supply Voltages-Terminal and Repeater . .. .. ... .................. 56 D-C Supply Voltages (sp.). 57 Plate Voltage Measurement" (sp.) .......... .. .. ... ... .... 57 Carrier Output Test. 57 Terminal Transmitting Gain. 59 Terminal Receiving Gain Test. 60 Gain Test- Repeater. 60 Supplementary Tests. 61 11. APPARATUS REQUIREMENTS AND ADJUSTING PROCEDURES . .... .. .... 62 General .. .. .......................... ..... ............... ... ...... 62 Tools, Gauges, Meters, Etc. .. 63 Keys .. ... .. ............................ .. ........... .. .... .. .. .. ... 64 Cleaning . .. 64 Adjusting . 64 Relays .. .. .. ... .. .. .......... ... .. .. .. ... ... ........ .. .. .. ... 65 General. ....... .. .. ... .. ...... .... ..... ... ... ..... .. .. ... 65 Requirements for R Type Relays. 67 Requirements for S Type Relays. 69 Requirements for 206BR Relays . 71 Vacuum Tubes .... ..... ...... ..... .... .. ... ....... .. .. .. .... .... ... ... 73 TCI Library https://www.telephonecollectors.info/ Western EltclTic Hl CARRIER TELEPHONE EQUIPMENT Instructions for Use 1. INTRODUCTION General 1.01 The Western Electric Hl Carrier Telephone System is a single­ channel system which pr0vides for superimposing an additional tele­ phone circuit upon an existing voice-frequency telephone circuit work­ ing over an open-wire line. The carrier equipment includes provision for operation on a ringdown basis and can be applied on a line without the loss of any existing service. It is suitable for use as a permanent installation and also for temporary or emergency circuits. Without an intermediate repeater, the system will find its widest application on open wire circuits of about 50-200 miles in length; with one or two intermediate repeaters it will be applicable on circuits up to as much as 500 or 600 miles in length (depending on the gauge of the open wire conductors, the amount of intermediate cable in the line, the number of bridged way stations, etc.) . 1.02 The Hl system employs copper-oxide modulators and demodu­ lators, heater type pentode tubes, and improved filters made possible by new magnetic alloys. The copper-oxide varistors used as modu­ lators, demodulators and rectifiers in 'the power supply are of smaller ·size than the customary vacuum-tube devices, have the advantage of long life and small power consumption, and provide better balanced and more stable modulation. A single heater­ type pentode tube in the transmitting amplifier works at approxi­ mately the same output level as two tubes in the older systems. It simplifies the problem of working from 110-volt a-c. suppiy by obtain­ ing grid biases from across a resistance in the cathode circuit. 1.03 The terminal unit and the repeater may be operated either directly from a 115-volt 50-60 cycle alternating current source or from 24-volt and 130-volt batteries. This system employs the same carrier frequency, 7150 cycles, for both directions of transmission. The car­ rier frequency is generated locally at each terminal and only the side­ bands are passed over the circuit. The upper sideband is used for transmission in one direction and the lower sideband for the other. 1.04 Because of the relatively short distances over which the system Instruction Bulletin No. 900 TCI Library https://www.telephonecollectors.info/ is designed to operate, no equalization is provided and no automatic regulation of the circuit net loss is employed. However, for the longer systems a manual compensating adjustment has been included in each terminal whereby the receiving gain may be changed in three steps of 2 db each. Similar arrangements are also provided to control the gain of a repeater, two steps of 4 db each being provided. These adjust­ ments will compensate for changes in loss due to weather and tem­ perature changes in the line. 1.05 It is necessary to compute and specify transmitting levels, repeater output levels, receiving levels, and circuit net loss for each Hl carrier circuit placed in service. This data should be based on the transmission performance of the carrier equipment and the character­ istics of the open wire line and intermediate cable over which the sys­ tem operates. Sufficient information for determining the required levels in the majority of cases has been included as a part this publica­ tion. The testing procedures herein presuppose that the levels have been determined and specified for the system which.