Patent GB-257329-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q1/26
Filed: 1925-05-26
Abstract: 257.329. Automatic Telephone Manufacturing Co., Ltd., and Saville; W. May 26, 1925. Automatic exchange systems. -Each district office has a special trunk 115, .116 leading to an observing operator's position at the main exchange. At the district office, the trunk terminates in a relay group FRG and finder switch FS, which makes connection to the relay group SRG 'associated with a subscriber's line. At the main exchange, the trunk terminates in a relay group TRG, which becomes connected to the observation position over a finder switch FS1 or FS2. ' If the observation equipment is free a calling or called line is automatically connected thereto, and lamp and tone signals are given to indicate various stages of the call, and in the case of a calling line, the dialled number is recorded on lamps. Means may be provided for the observing operator to ascertain the number of the line under observation. The equipment remains locked to the line last observed unless released therefrom by the operator by means of key RD. The finder FS2 is normally in use, and the finder FS1 may be substituted by means of key CO in the event of a fault occurring. Connection of calling line to observation position. The line relay of the subscriber's line switch energizes over wires 3, 5, upper winding of relay 7 and relay 14. Relay 7 is polarized and is inoperative, but relay 14 operates, and connects up relay 17 and lower winding of relay 20 in parallel. Slow relay 17 does not operate since its circuit is opened by relay 20, which also locks over its upper winding to the test wire 4, and grounds wire 56. Relays 282, 280, 281 now energize to remove battery from all other relays such as 20 to prevent any other line obtaining access to the observation equipment. If the equipment is in use when a call is initiated, relay 17 energizes and locks up, preventing the line being connected to the equipment at any later stage. Ground on wire 56 operates relav 73 (lower winding), which closes the driving circuit for magnet 54 through supervisory relay 34 and test relay 68, which is connected to test wiper 53, and the finder FS hunts for the calling line, which is marked by the removal of ground from test terminal 49 by relay 20 at contact 24. Ground on wire 56 also extends over relay 112, trunk wire 116 and wire 118 to relay 126, which energizes and connects up relays 132, 147 (upper winding) and lights the trunk calling lamp 204 over wire 167. Provided the observation equipment is free, there is no ground on wire 163, so that relay 147 is not short-circuited and operates, locks over its lower winding and grounds wire 163 to guard the equipment. Relay 144 also energizes over wire 168 and key RD and connects up relay 119, which extends wire 117 to relay 129, and relay 272, which provides a further ground for relay 147 over wire 162. Ground on wire 163 completes the driving circuit for magnet 208 and test relay 209 through key CO and supervisory relay 222, relay 209 being connected to test wiper 223, and the finder FS2 hunts for the trunk relay group TRG, which is marked by the removal of ground from test terminal 170 by relay 144 at contact 155. Test relay 209 energizes when the marked test terminal is reached, connects up certain wipers and lights the trunk engaged lamp 203 over wires 166, 169 and key 215. Relay 235 now energizes over wiper 282, and connects up relay 237, which locks and prepares the number recording apparatus for use. When the calling line is seized by the finder FS, test relay 68 operates and connects up relays 77 (upper winding), 87, 106, but relay 77 being polarized is inoperative. Relay 106 energizes, and connects up relay 109, which at contact 110 completes a bridge across the trunk 115, 116 through relays 112, 77 (lower winding). At the main exchange, the trunk is connected over wires 117, 118 to relays 126, 129, and the latter now energizes, disconnecting calling lamp 204 and lighting a white position lamp 201 over relay 135, which energizes and locks. The operator's receiver 230 is now connected to the calling line over wires 259, 260, wipers of the finder FS2, wires 117, 118, trunk 115, 116, contacts 110, 108<1>. and wipers of the finder FS. Recording of dialled number. Relay 14 responds to dialled impulses, and at contact 15 controls relay 109, sluggish relay 102 being energized at the first impulse to short circuit relay 77 and retardation coil 81. Impulses are repeated by relay 109 over the trunk at contact 110 to relay 126, which through relay 235 controls magnet 254 over wiper 252 of the distributing switch M and series relay 245 to set the first digit register M1. Sluggish relay 243 is controlled by relay 245, and these relays relapse in turn at the end of the train, sending an impulse to magnet 251 to advance the switch M to the second digit register M2, which, upon moving off-normal, closes a circuit over wipers 264, 263 and the selected terminal to light the first digit lamp. Subsequent digit lamps are lighted in a similar way, the circuit for the last digit lamp being over a back contact 246 of relay 245 and wiper 271. Reply of called party. Polarized relay 7 energizes upon reversal of line current, and connects up relay 9, which closes a circuit over wire 60 for relay 82, which locks, disconnects relay 87 and connects battery to wire 116 to short-circuit relay 126. Relay 126 falls back and closes a circuit over wiper 253 and wire 159 for relay 141 (lower winding), which locks. When relay 87 falls back, relay 95 energizes over wire 63 and the metering wire 6, disconnecting relay 82, removing battery from wire 116 and locking by cutting out resistance 94. Tone current is connected through condenser 90 to wire 116 and thence to the operator's headset to indicate that metering has taken place, while the subscriber's line is momentarily short-circuited at contact 96 until relay 82 falls back. Relay 126 re-energizes and lights a red position lamp 202 over wire 165. Release by called party. Relays 7, 9 fall back due to reversal of line current, sluggish relay 95 is disconnected, and battery is connected over wire 64 to wire 116 until relay 95 relapses, shortcircuiting relay 126 and extinguishing red lamp 202 momentarily. Release bv calling party. Relay 14 falls back, releasing relay 109, which at contact 110 opens the bridge across the trunk 115, 116. Relay 20 falls back when ground is removed from the test wire 4. Relay 73 (lower winding) holds over wiper 50<1>, maintaining relays 68, 87, 106, 282. so that battery is withheld from all relays such as 20. When the trunk loop is opened relays 126, 129 fall back, releasing relays 132, 135, 141. Relay 144 remains locked over wire 168 and key RD, and holds relay 147. Relay 235 is released at contact 128, and disconnects relay 237, and circuits are completed for the release magnets of the switches M, M1-5. Relays 126, 135, extinguish white and red lamps 201, 202, but trunk engaged lamp 203 is maintained lighted by relays 147, 209. The observation equipment remains locked to the line last observed. Observation equipment in use. In this case, wire 163 is grounded, and when relay 126 pulls up, relay 147 is unable to operate. Relays 144, 119 do not energize, and when the bridge across the trunk 115, 116 is completed, there is no circuit for relay 112, so that it relapses and connects up relay 17 over wiper 52 and wire 58. Relay 17 locks to the test wire 4 and prevents energization of relay 20 during the call. Connection of called line to observation position. A branch of the ringing circuit extends from wire 5 through a condenser to the upper winding of relay 29, which responds and at contact 30 connects up relay 20 (lower winding). If the finder FS is not in use or locked, relay 20 energizes and connects up relay 73 to start the switch as before. Relay 29 locks over its lower winding and grounds wires 56, to start the finder FS2 and light calling lamp 204. Relays 87, 106 energize when the test relay 68 pulls up, and relay 102 operates in this case. Relay 87 connects up relay 82 over wire 60, and this relay locks over wire 59 to the test wire 4, disconnects relay 87, and connects battery to wire 116 to shortcircuit relay 126 momentarily until relay 87 relapses to energize relay 141 (upper winding). Relay 141 locks and lights red lamp 202 over wire 165. Relay 87 also energizes relay 65 over wires 57, 59. This relay locks over wire 61, and when relay 87 falls back, ground is connected to wire 116 to operate relay 126 again. Relay 112 is cut out at contact 108', but the circuit of relay 17 is open at contact 103. Reply of called party. Relay 14 energizes and connects ground over wiper 52 to energize relay 109, which disconnects relay 102 and closes the trunk bridge at contact 110. Relay 129 energizes, and connects up relay 135, extinguishing calling lamp 204 and lighting white lamp 201. The operator can ascertain that conversation is proceeding satisfactorily. Release by called party. Relay 14 falls back and releases relay 109, which opens the trunk bridge, but completes a fresh circuit for relay 126 over wire 116. Relays 129, 135 relapse cutting out white lamp 201. Engaged lamp 203 and red lamp 202 remain lighted until the calling party hangs up, when relays 20,29 release. The equipment as before remains locked to the line last observed. Observation train faulty. The operator presses the change-over and hold key CO. This connects ground to wiper 277 to energize relay 121, which reverses the connections to relays 126, 129 and disconnects relays 132, 135 and the various lamps, so that the trunk relay group TRG is released from the observation equipment. Relays 144, 119 fall back, removing ground from wire 160 to release relay 272, which in turn removes ground from wire 162 to release relay 147. Calls over other trunks may now be dealt with over the finder FS1, which is substituted for the finder FS2 by key CO, t