TRAFFIC CONTROL TELEPHONE SYSTEMS Circuit - Sam Hallas

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CONTENTS Part Title Page 1 Key System, Circuit Description ......................................................... 4 2 Selector Key, 4001-A ........................................................................... 17 3 Selector, 4304-A and 4301-A ............................................................ 24 4 Selector Test Set, 4001-B .................................................................. 35 5 Dial System, Circuit Description ....................................................... 39 6 Line Construction and Line Voltage Curves .................................. 50 7 Line Test Set, LU.3101 ...................................................................... 53 8 Relays, Adjustment of .......................................................................... 64 9 Line Switch, 4120 Type ..................................................................... 73 10 Line Switch, 4150 Type ..................................................................... 78 11 Adjusting Tools..................................................................................... 84 LIST OF ILLUSTRATIONS Figure Title Page 1 General Schematic Key Sending System ............................ (facing) 8 2 Selector Circuit operated through a No. 341-A or AAJ 4100-1 Transformer ............................................................... 12 3 Selector Circuit operated through 2 Q.4104-1 or 2 No. 70A Repeating Coils in Series ................................................................ 12 4 Branch Line operated through Repeating Coil .............................. 13 5 Intermediate Telegraph Station . ..................................................... 13 6 Selector Key Case (Capacity 40 Keys) ............................................ 17 7 Selector Key, illustrating method of coding ................................... 18 8 Selector Key, 4001-A ........................................................................... 21 9 Selector 4304-A .................................................................................... 24 10 Selector 4301-A exploded views........................................................ 32 10a Selector 4304-A exploded views........................................................ 34 11 Selector Test Set, 4001-B ................................................................... 35 12 Selector Test Set, Schematic .............................................................. 37 13 Dial System, Schematic .......................................................(facing) 84 14 Line-Voltage Curves-direct signalling............................................... 51 15 Line-Voltage Curves-signalling through one transformer ............ 52 16 Line-Voltage Curves-signalling through two Repeating .................... Coils ......................................................................................................... 52 17 The Line Test Set ................................................................................. 53 18 Line Test Set-Battery Voltage Test, Schematic . ........................... 55 19 Line Test Set, Resistance by Wheatstone Bridge Test, ..................... Schematic................................................................................................ 56 20 Line Test Set, Earth Fault by Murray Earth Test, Schematic .... 5 8 21 Line Test Set, Resistance by Voltmeter Test, Schematic ............. 5 9 22 Line Test Set, Volts, Resistance Curves .......................................... 60 23 Line Test Set, Selector Circuit Impulse Ratio Test, Schematic.. 61 24 Line Test Set, Reduced Voltage Test for 4301-A and 4304-A ......... Selectors Schematic .............................................................................. 62 25 Line Test Set, Telephone and Ringing Circuit, Schematic .......... 6 3 26 The B.P.O. type Relay ........................................................................ 65 Page 3
Page 4 PART 1 KEY SENDING SYSTEM DESCRIPTION GENERAL Selection of the required way station is obtained by a coded train of impulses, normally comprising three groups. The sum of the impulses in the three groups is the same for all codes, and the receiving apparatus is designed to respond only to the correct total, so that lost or additional impulses (due to external interference) cannot cause wrong calls. The constant total feature ensures that line interference cannot establish a wrong call but would make that call ineffective. The presence or absence in the Controller's receiver of "ring back" tone, generated by the way station bell, immediately advises him of either the completion or failure of the call. Selector Key No. 4001-A The function of the selector key is to control the operation of the battery and battery reversing relays which switch the line battery and transmit the appropriate sequence of current impulses to the line. The 4001-A Selector Key is fully described in Part 2, and this should be read in conjunction with the circuit description on page 8. Battery Relay 4664-DA This relay designated BR, applies the line battery to the line before impulsing commences and switches off after the end of the ringing period. The operation of BR is controlled by the selector key. Battery Reversing Relay 4664-MX This relay, designated SR, reproduces the impulses originated by the selector key, reversing the polarity of the line with each impulse. A train of impulses therefore consists of a succession of pulses of alternating polarity. The adjustment figures for the 4664-MX Relay are given at the end of Part 8, and attention is drawn to the two notes relating to any adjustments made to this relay. It is important that the impulses due to line battery reversals sent out by SR to line should be of equal duration. The impulse ratio can be determined quite closely by observation, but more accurately by use of a centre zero voltmeter or a centre zero milliammeter with a resistance in series to limit the current. The meter should be connected directly across the line terminals and an uninterrupted train of impulses, such as the General Call code should be transmitted. If the impulse ratio is correct the
Page 2 and 3: TRAFFIC CONTROL TELEPHONE SYSTEMS C
Page 6 and 7: swing of the meter needle either si
Page 8 and 9: One No. 4002-B Selector Key Case (c
Page 11 and 12: wires. This change of polarity is t
Page 13 and 14: Case), K2 terminal (Time Sending Se
Page 15 and 16: Where satisfactory operation cannot
Page 17 and 18: one is available (if not, with an o
Page 19 and 20: PART 2 4001-A SELECTOR KEY Selector
Page 21 and 22: The keys are easily removed from th
Page 23 and 24: Letter. Name. S.T.C. Code. A Impuls
Page 25 and 26: 4. When the key is normal the tip o
Page 27 and 28: the time terminal. During selective
Page 29 and 30: Cycle of Events on Receiving a Code
Page 31 and 32: Mechanical Requirements To assist i
Page 33 and 34: (b) The contact spring (Z) in the n
Page 35 and 36: Letter Name 4301-A 4304-A 4305-B A
Page 37 and 38: General PART 4 4001-B SELECTOR TEST
Page 39 and 40: 4001-B Selector Test Set, Schematic
Page 41 and 42: General PART 5 DIAL SYSTEM, SELECTI
Page 43 and 44: The speak key also connects the con
Page 45 and 46: normal, Relay IR is held operated a
Page 47 and 48: here that from SC bank contacts 29
Page 49 and 50: from Line switch SC banks 1 and 2 a
Page 51 and 52: Line Test Set . . . . . . Designed
Page 53 and 54: Line Voltage Curves Fig. 14. The op
Page 55 and 56:
General PART 7 LINE TEST SET-LU.310
Page 57 and 58:
Operating Instructions 1. Voltage M
Page 59 and 60:
the particular line to the earthed
Page 61 and 62:
Operate CVK, note meter reading on
Page 63 and 64:
10. Impulse Ratio Check on Selectiv
Page 65 and 66:
12. Telephone Communication. (See F
Page 67 and 68:
Page 65
Page 69 and 70:
Armature Travel Armature travel is
Page 71 and 72:
Contact Sequence The standard conta
Page 73 and 74:
chloride or trichlorethylene. The t
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PART 9 ADJUSTMENT AND MAINTENANCE D
Page 77 and 78:
9. Armature Restoring Springs:— T
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Oil dag should be applied as above
Page 81 and 82:
3. Pawl Spring Tension 3.1 With the
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8.6 The wipers shall exert a pressu
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2.2 The wipers shall rotate smoothl
Page 87:
Registered Office: CONNAUGHT HOUSE
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TRAFFIC CONTROL TELEPHONE SYSTEMS Circuit - Sam Hallas

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