Patent GB-155877-A (GB)
Title: Improvements in electric telegraph systems
IPC: H04L25/49
Filed: 1919-08-28
Abstract: 155,877. Western Electric Co., Ltd., (Western Electric Co., Inc.). Aug. 28, 1919. Distributor systems; synchronous movements; type-printing telegraphs. -In a type-printing telegraph system of the kind in which combinations of positive and negative impulses are sent to line by means of it perforated-strip transmitter, means are provided for suppressing successive current impulses of like polarity and earthing the line during the periods of the suppressed impulses, thereby reducing the static charge upon the line. In a modification, additional means are provided for placing resistance units in parallel with the line when a current impulse of a polarity opposite to that of the suppressed impulses is sent to line, the number of resistance units introduced being equal to the number of preceding suppressed impulses, thereby reducing the potential of the applied impulse. The apparatus may be used on multiplex systems of the distributor type and means are provided for sending positive and negative synchronizing impulses to the receiver distributor during the inoperative periods of the transmitter. The transmitting system of one channel of a multiplex system comprises a series of type-actuated contacts 1, 11, 21, 31 and 41, Fig. 1, normally occupying the positions shown, a series of relays 2, 12, 22, 32, and 42 controlled by the tapeactuated contacts and controlling the polarity of the current supplied to the contact segments 8, 18, 28, 38, and 48 of a rotary distributor D, and a series of compound-wound relays 5, 15, 25, 35, and 45, each controlled by two adjacent tapeactuated contacts and adapted to connect the contact segments of the distributor D to the positive or negative leads 29, 19 through the contacts of the relays 2 - - 42 or to connect the segments to earth through the lead 89 and resistance 90. A similar transmitting-system for a second channel is shown on the right-hand side of the line 69. The relays 15 - - 45 and 65 - - 95 are normally energized and the relays 5 and 55 are normally deenergized. Suppose the tapes of the systems be punched to send the series of impulses shown in the upper diagram of Fig. 2 so that the contacts 11, 21, 51, 71, and 81 are actuated. Under this condition the relays 5, 25, 45 and 85 allow their armatures to remain in the positions shown, the relay 55 attracts its armature, and the relays 15, 35, 65, 75, and 95 release their armatures to engage their back contacts. The relays 12, 22, 52, 72, and 82 are operated since they are placed in series with the batteries 50, 60, acting in conjunction instead of in opposition. When the brush 40 engages the segment 8, a negative impulse, shown in the lower diagram of Fig. 2, is sent to line 99 from the battery 20 over lead 19, contact 3 of relay 2, contact 6 of relay 5, segment 8, brush 40, and ring 39. When the brush 40 engages the segment 18 a positive impulse is sent to line 99 from battery 30 over lead 29, contact 14 of relay 12, contact 16 of relay 15, segment 18, and so on. When the brush 40 engages the segment 28 the positive impulse which would be sent normally is suppressed since the circuit between the lead 19 and the segment 28 is broken at the contact 26 of the relay 25, and the line 99 is earthed through the contact 27 of relay 25, lead 89, and resistance 90. Similarly a negative impulse is sent to line when the brush 40 engages the segment 38 and the line is earthed while the brush engages contact segments 48 and 58. Operations similar to the above occur as the brush 40 passes over the remaining segments of the distributor D, thereby sending current impulses to line in the order shown in the lower diagram of Fig. 2 instead of as shown in the upper diagram of this Figure. In the modification shown in Figs. 3 and 4, which show respectively the transmitting arrangements of a two-channel system, one transmitting arrangement comprises a series of tapeactuated contacts 1 - - 5, Fig. 3, normally occupying the positions shown, a series of relays 11 - - 15 controlled by the tape-actuated contacts and controlling the polarity of the current supplied to the contact segments 71, 52; 72, 53; &c. of a rotary distributor, a series of grounding relays 21 - - 25 controlled by two adjacent tape-actuated contacts and adapted to connect the contact segments 71, 52; 72, 53; &c. to earth or to the armatures of the pole-changing relays 11 - - 15, and a series of relays 31 - - 35 which in conjunction with a master relav 140 control resistance units 146 - - 150 to place these resistances in varying numbers in parallel with the cable L, Fig. 4, in accordance with the number of impulse periods during which the cable L has been earthed by the suppression of successive impulses of like polarity. A record transmitting arrangement shown in Fig. 4 comprises similar sets of contacts, relays, and resistances, a split battery 104, 107, and polarized relays 112 and 116. The grounding relays 21 and 26 are normally energized from a battery 101. Suppose the tapes of the systems be punched to send alternate negative and positive impulses by the system shown in Fig. 3 and three successive positive followed by a positive and a negative by the system shown in Fig. 4. This results in the operation of the pole-changing relays 12, 14, and 19, and the grounding relays 21 - - 26, 29, and 30. The non-operation of the relay 11 and the operation of the relay 21 connects the distributor segments 71, 52 to the negative pole of the battery 104 over resistance 105, lead 106, back contact of relay 11 and front contact of relay 21. When the brush 127 engages segments 71, 81 a negative impulse is sent over lead 135 to line L, while the relay 116 is operated to close the contact 118. The operation of the relays 12 and 22 connects the distributor segments 72, 53 to the positive pole of the battery 107 over resistance 108, lead 109, front contact of relay 12, and the front contact of relay 22, so that when the brush 127 engages contact segments 72, 82 a positive impulse is sent over lead 135 to line L; while the relay 116 is operated to close the contact 117. The brush 126 bridges distributor segments 52, 62 to energize the relay 31 over the lead 124 and the master relays 140 and 160 in parallel. The operation of the right-hand armature of the relay 31 closes a locking circuit for the relays 31, 140 and 160 from the battery 110 over contact 114 of relay 112, lead 115, right-hand armature of relay 31, lead 124 and relays 140 an4 160 in parallel. Since however the successive impulses are of opposite polarity the operation of the relays 31, 140, 160 and 116 is idle with respect to the resistances 146 - - 150 and 166 - - 170. Similar operations will occur during the transmission of the remaining impulses of the first channel and the first impulse of the second channel since these impulses are alternately positive and negative and the relays 31 - - 35 and the relays 140 - - 160 are released successively by the operation of the relay 112. When the brush 127 engages distributor segments 77, 87 the line L is earthed through the back contact of relay 27 and the grounded conductor 121, thereby suppressing the second successive impulse of positive polarity. At this time the brush 126 connects the distributor segments 67, 57 to energize the relay 112 with positive current to open the locking circuits of the relays 35, 140 and 160 at the contact 114 while the relays 36, 140 and 160 are energized over the contact segments 57, 47. The relays 36, 140 and 160 are locked up over the contact 113 of relay 112. Since the next impulse is also of positive polarity the line L is again earthed over the distributor segments 88, 78, the back contact of relay 28, and the conductor 121. The relays 37 and 112 are not operated since the contact segment 58 is earthed so that the relays 36, 140 and 160 remain locked up. The next impulse being negative a circuit is established between the battery 104 and the line L over the resistance 105, lead 106, front contacts of relays 19 and 29, distributor segment 70, brush 127, and segment 89. The contact 59 remains earthed over the back contact of relay 28. The negative impulse on the line causes the relay 116 to operate to close its contact 118, thereby shunting a portion of the current from the battery 104 through the conductor 106<1>, contact 118 of relay 116, resistance unit 167, contact 162 of relay 160, left-hand normal contact of relay 27, and the righthand front contact of relay 36 to earth and through a parallel circuit through resistance unit 168, contact 163 of relay 160, and the left-hand normal contacts of the relays 28 and 37. When the brush 127 engages distributor segments 80, 90 a negative impulse is sent to line and the relays 36, 140 and 160 are released by the operation of the brush 126. If the line L be grounded during the period of one signalling impulse only one resistance unit will be placed in shunt with the line, and generally the number of resistance units shunting the line is the same as the number of impulse periods during which the line is grounded. During the inoperative periods of the transmitters positive and negative synchronizing impulses are sent to line, since under this condition the relays 21 and 26 are in their operative positions, and a. negative impulse is sent to line L when the brush 127 engages segments 71, 81 and a positive impulse is sent to line when the brush engages segments 76, 86. In a single-channel system the connections between the leads 102, 103 to one of the sets of tape-actuated contacts is reversed and a similar reversal made in the connections of the corresponding pole-changing relay.