Patent GB-328951-A (GB)
Title: Improvements in and relating to automatic or semi-automatic telephone exchange systems
IPC: H04M3/30
Filed: 1929-02-07
Abstract: 328,951. Standard Telephones & Cables, Ltd., and Wright, E. P. G. Feb. 7, 1930. Automaatic exchange systems. - Single-motion switches are used as test distributors and as test final selectors. The switches are set under the control of common marking switches, arrangements being made for the final selector to be controlled directly by impulses after the initial setting has been made. A busy signal is returned if either switch meets a busy condition. Distributor. The application of earth over wire T operates IK in series with both windings of relay 12 (via N2), the switching being effected only if the wipers of the control switch are in the home position. Relays 1A and PC operate in series over the calling loop, allowing 1B to pull up. The first impulse series are repeated by 1A to the group marking switch ITC in series with relay 13. Relay 13 allows relay 15 to operate its light armature 1 and completes a circuit for the magnet S of the distributor, stepping the switch until its wiper C reaches the contact marked by wiper ITC1 when relay 16 pulls up to break the circuit of S. When the impulse train ceases relay 13 relapses and relay 15 operates over both its windings in series changing over the pulsing circuit to magnet IUC and locking relay 16. The next impulse train is repeated to IUC and relay 13, operating in series, enables relay 17 to operate its armature 3. This relay operates fully when the train ceases, re-completing the circuit for magnet S to step its wipers until C reaches the contact marked by IUC1 which operates relay 18 to stop the drive and to break the circuit of relay E which operated when relay 17 pulled up. Relay 18 breaks the circuit of relays IK and 12 which release, unlocking 15, 16, 17 and 18 and allowing IUC and then ITC to return to normal and free the control switch for use with another distributor. When relay E operated slow-release relay TD pulled up and during the interval between the release of TD and E relay RR is extended to wiper P2. If the circuit on the control circuit is busy, RR operates from ground on the wiper breaking the circuit of PP and reversing the current flow over the calling loop to signal the test clerk. If the line is free, however, slowoperating relay PP operates over its lower winding, switching the circuit through and connecting relay RR to wiper P2. Final selector. The further impulse series are repeated to relay 2A by 1A and first magnet 2TC and then magnet 2UC step the control switch, relays 23, 25, 26, 27 and 28 acting to step magnet S2 and to release, the control circuit in the same manner that relays 13. 15, 16, 17 and 18 controlled magnets S and the distributor control circuit. Relay E re-operated during impulsing from the back contact of A completing a circuit for TD and consequently during the period between the release of these two relays RR is connected over wiper PI to test the selected circuit. If the line is busy, earth on T, Fig. 2, enables RR to pull up to signal the condition as before. If the line is free, TD releases and a metallic circuit to the called line is extended over wires +T and -T. When relav 2K has released, further impulses are repeated by 2A directly to magnet S2.