Patent GB-303575-A (GB)
Title: Improvements in or relating to semi-automatic telephone systems
IPC: H04M3/60
Filed: 1927-10-10
Abstract: 303,575. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. Oct. 10, 1927. Semi-automatic exchange systems.-In a system in which calls from manual to automatic exchanges are set up by an A operator, a dial switch is associated with a particular cord circuit by operation of the speaking key and movement of the dial off normal, and remains associated with the cord circuit until the key is restored. The normal connections of the supervisory and battery feeding relays of the cord circuit to both calling and answering ends remain unaltered during impulse sending. The speaking wires of the cord circuit are connected together when the dial is off normal, impulses being sent to a repeater at the outgoing end of a junction by intermittent application of earth to the speaking wires. When operator receives a call she inserts answering plug 18 of standard cord circuit CC throws speaking key 16, ascertains wanted number, and inserts calling plug 19 into jack 20 of a free junction 60, 61. One of the jacks of a group, that shown, has busy tone conductor 62 connected to its sleeve over the contacts of armature 44 of sleeve relay 37 and over contacts of the other sleeve relays of the group so that if all junctions of a group are busy, operator receives busy tone when testing the master jack. If, however, she only receives the ordinary busy signal from the master jack, she proceeds to test the other jacks of a group. Dialling circuit DC is connected up to the end circuit by movement of the dial off normal which completes a circuit over springs 25 for relay 23 which at 30 completes circuit of relay 22 over springs 26. The leads 8, 9 to the speaking wires of CC are connected together at 28 and to the impulse springs 24 at 27, the wires 8, 9 being also disconnected from the speaking circuit SC, and lamp 21 is lit. Relay 23 is held at the end of impulse trains over 25, 27, 9 and 11. Accidental operation of the dial switch while operator is speaking to subscriber is indicated by lamp 21, and the speaking circuit may be restored by operation of Key 26. Repeater R. Relay 39 and shunt-field relay 40 are connected across junction 60, 61 at 47 by relay 37. Relay 43 operates over 56, 31, 8 and 11 and completes a circuit over 52, 59, 54 for relay 41 which locks up and at 52, 54 connects armature 59 of relay 43 across the junction. During dialling, the normally open springs 24 intermittently short-circuit relay 43 which at 59 repeats the impulses over junction 60, 61, and when dialling is completed, speaking key 16 is restored. Relay 38 now operates over 57, 51 in series with relays 10, 11 of CO and at 48 completes a circuit for relay 42 which locks up, disconnects relay 43 at 56, and holds the connection to the automatic exchange over 55 and relays 39, 40. Relay 38 is also brought down at 57. When called subscriber replies, shunt field relay 40 connects 38 across conductors 31, 32 to operate relay 10 which gives the usual supervision at 14. Busy signal. Relay 39 is released and operated intermittently by busy flash from the automatic exchange causing relay 10 to operate intermittently over 49, 50, 57, relay 38 and conductor 31 to flash a lamp. The calling subscriber also receives busy tone.