Patent GB-260677-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1925-08-05
Abstract: 260,677. Automatic Telephone Manu facturing Co., Ltd., (Automatic Electric Co.). Aug. 5, 1925. Automatic and semi-automatic exchange systems. - A calling prepayment line at a small unattended exchange is extended automatically to an operator's position at another exchange, and the operator completes the connection over automatic switches at the originating exchange if the call is local or to a neighbouring exchange, or over a cord circuit in the case of a trunk call, and supervises the deposit of a coin in the coin-box. In the arrangement described, apparatus TC is associated with each selector S available to prepayment lines, and causes the call to be extended over a finder switch F and a trunk TL to an operator's position TC<1>. In certain cases, the apparatus TC may be connected directly to a trunk TL. Local call. When the test wire 49 is grounded upon seizure of the selector S, relay 31 energizes, and extends the calling line to line relay 32, line relay 81 being held over jumpers 51, 54. Relay 64 also energizes over the test wire 49, grounding the start wire 70 and connecting cut-off relay 65 to wire 62. Relay 102 energizes and connects up magnet 101 and switching relay 103 to start the finder F in search of the apparatus TC. When this is reached, relay 103 energizes, locks to the test wire 49 over wire 61. and switches through, releasing relay 102 and extending start wire 70 to outgoing start wire 170. Cut-off relay 65 energizes, wire 62 being now grounded, disconnects start wire 70 and opens the circuit of line relay 81, which however holds over the trunk TL, jack J and relay 142, which lights lamp 148. The operator throws her answering key K<1>, connecting the listening and calling device in place of relay 142, and relay 141 energizes. Operation of the switching key K energizes relay 34 over wires 60, 125, closing the talking circuit to the calling party and completing a local holding circuit for line relay 81. On finding that a local connection is desired, the operator restores key K, releasing relay 34, and operates her dial 150 to set up the connection. She re-establishes communication with the calling party by means of key K, and tells him to deposit a coin, and a vibratory spring struck by the falling coin emits a musical note audible to the operator, who then restores keys K, K<1>. Wires 124, 126 are now both grounded, so that differential relay 36 is unbalanced and operates, connecting up relay 37, which locks and releases relay 31. The calling and called parties are now in communication. Ground is removed from wire 61, causing relays 64, 65, 103 to relapse and restore the trunk TL to common use. Trunk call. If, on enquiry, the operator learns that a trunk call is desired, she completes the connection over jack J by means of a cord circuit. Keys K, K<1> are restored, but relay 34 holds over jack J. Wires 124, 126 are disconnected from relay 142 and extended to the supervisory feed relay, which energizes. When the calling party hangs up, line relay 32 falls back, and opens the bridge across wires 124, 126 to give a disconnect signal. The operator clears, and relay 34 relapses, opening the local holding circuit of line relay 81. Ground is removed from the test wire 49 and the whole connection is released.