Patent GB-334534-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/62
Filed: 1929-06-04
Abstract: 334,534. Associated Telephone & Telegraph Co. Dec. 24, 1928, [Convention date]. Automatic and semi-automatic exchange systems.-Switches that operate as call-finders or as connectors are restored to normal only when seized for use as connectors. The invention is described with reference to a private office with two-way junctions terminating in the, privateoffice in these switches. Incoming calls are set up by an operator except at night when a particular subscriber is given sole use of one of the junctions. Local call. When a subscriber calls, common line relay LR pulls up in series with individual line and cut-off relay 4 which pulls up its armature 6 to mark the line. Relays 15, 12 pull up and magnet 23 drives the finder F, until a circuit is made over the test wiper for relay 4 in series with a reverse winding of 12 which falls back and with 13 which energizes 16 to extend the talking circuit, transfer the start circuit to the other link, and hold 14, short-circuiting 13. 13, 15 fall sluggishly, and impulse relay 17 and release relay 18 pull up. Dialling tone goes back from DT. The digit is repeated to magnet 24 and dialling relay 19. If the line is busy, 21 pulls up and sends back busy tone from BT. If it is idle the relapse of 19 connects the test wiper to 22 which locks up and cuts off the dialling tone. The calling party then rings by dialling 2 or 8. 19 pulls up and energizes busy relay 21 which now connects up ringing current from GEN. At the end of the digit 19, 21 fall and stop the ringing current. The use of a long or short digit may be used as a code for calling a subscriber on a party-line. When the called party replies 20 switches the talking circuit through. When both subscribers have hung up, 17, 18 fall and the connector goes home. Outgoing call. The subscriber dials O and on the relapse of 19 switching relay 22 in the link pulls up in series with start relay 110, Fig. 2, which energizes 107 to operate driving magnet 105 of the finder TF. When TF finds the calling- line which is marked via wipers 74. 11, the releasing winding of 107 is energized in series with 108 (which energizes 109) and 14 which releases the local link. 109 transfers the start circuit to the next trunk circuit and extends the loop via 111 to the main office. 111 responds and energizes release relay 112 which energizes 113 via the main office. 113 locks and completes the loop to the main office at which a line switch seizes a selector which is controlled by the subscriber in the usual way. When the calling party hangs up 111, 112 relapse and then 113. 109. If both junction circuits TC are busy, the common relay 186 pulls up partially in series with 22, contact X operating 20 which locks up. An instant later 22 connects direct ground to 73 and 186 then pulls up completely and sends back busy tone from 192. If the other connector is set to its 10th terminals at this time it behaves as when set to a busy local line. Incoming call. When a connector seizes the junction 170, 171, 116 responds when ringing cur. rent is sent out and 115 during the ensuing silent period. 116 locks itself and lights 203 in series with 207 which operates the buzzer 22,2 (provided the keys AK of the other junctions are in their normal position). 115 energizes 114 which energizes 113 to switch the starting circuit to the next junction circuit. The operator removes her handset operating cradle springs 201, 202 and throws AK. 230 pulls up over the dial springs and 117 on the junction circuit pulls up over AK which also energizes 229. 117 shunts resistances 155, 156 to operate the ring-trip relay in the calling connector and homes TF. The operator can now talk with the calling party. As soon as TF is home, 106 the upper winding of which was previously short circuited, pulls up and energizes release relay 228 in the common apparatus CTR. The operator now dials and 230 repeats the impulses to magnet 105 and dialling relay 227. If the line is busy 226 pulls up and lamp 204 fails to light. If it. is idle or (if the main office chooses to wait) when it becomes idle, 225 is energized in series with the cut-off relay, energizes switching relay 109 (which lights 204), and grounds 176 to operate the cut-off relay fully. The operator then rings by dialling. Dialling relay 227 energizes 226 which connects up ringing current on GEN. When the called party replies- 224 pulls up releasing 106 which completes the talking circuit energizing 111 which is followed by 112 which releases 116 and puts out 204. Transfer of incoming call from subscriber A to subscriber A<1>. Subscriber A depresses his switch-hook intermittently for periods long enough to release. 112. 204 is thus flashed. The operator answers by throwing AK and 230, 229, 228 pull up. After informing the operator that A<1> is wanted, A hangs up and the operator then temporarily presses her switch hook, removing ground from 183 to unlock 109. 116 pulls up and lights 203. The operator then lets go the. switch hook whereupon a homing circuit is made for TF. After this the operation is as described in the preceding paragraph. Release of incoming call. When the local subscriber hangs up, 111, 112 fall back and 204 glows. The operator then throws RK releasing 109, 117. The main office connector is released by the re-insertion of resistances 155, 156 (provided the calling party has cleared). 114, 113 fall and the junction circuit is now in normal condition. Local call to or by operator. The operator is called in the same way as a local subscriber but before answering throws key LK to connect her set to line. She calls by throwing LK and removing her handset whereupon a local call finder hunts for her line as for an ordinary one. Night service. On going off duty the operator removes her handset and throws the key AK of one of the junctions and seizes it by throwing its key NK. 228, 229, 230 pull up and also 115 and ground is put on 179. 114, 113, 117 pull up, the latter homing the switch TF and energizing 116 which lights 203. 106 pulls up when TF is home and the operator now dials TF to the particular line that is going to take night calls and 225, 109 pull up and the latter looks up. The operator then restores her circuits to normal and 106 falls and marks the line busy. The night service line is now connected to the main office. and the subscriber can make and receive calls as if he were an ordinary main office subscriber..