GB254087A - Improvements relating to automatic and semi-automatic telephone systems - Google Patents

Abstract

254,087. Siemens Bros., &. Co., Ltd., and Patterson, W. G. June 10, 1925. Automatic and semi-automatic exchange. - systems.-Upon the receipt of the first impulse of a train the impulse relay at an impulse receiv. ing position is bridged across the speaking conductors to respond to loop impulses, but on the cessation of the train it is re-connected between one conductor and earth, leaving the other conductor available for the transmission of supervisory signals. In a modification which is referred to, the relay bridged across the line wires during trains of impulses is only used to take the impulses, and a separate relay is used for preparation and holding purposes. In the system described, a feed bridge first selector with battery connected over a retard coil to the outgoing bwire and earth connected over a supervisory relay to the outgoing a-wire, impulses over the b-wire in the usual manner when the connection is ex. tended over local switches, but impulses over a forward loop in the following manner on taking into use a junction to another exchange. When the junction a, b is seized, the impulse relay A is energized over the b-wire, and completes a circuit for the release relay V, which locks over contact v4, connects up dialling tone DS, and lights a lamp UL to indicate that no impulses have yet been received. On the receipt of the first impulse, the relapse of relay A energizes diallying relay D and the vertical magnet VM. Relay D disconnects ground from the winding 1 of relay A and bridges both windings of this relay across the a- and b-wires so that for the remaining impulses loop impulsing is employed. When relay A pulls up after the first impulse, a relay L energizes over off-normal contacts k3, locks over contacts l1, y1 and extinguishes lamp PL. At the end of the impulse train, relay D relapses, disconnects the winding 2 of relay A from the awire and again earths the b-wire over winding 1, and closes a circuit for the rotary magnet RM. Further impulse series are sent over the junction in a similar manner and repeated at contacts a3, the leg condition being reverted to after each series. When the called party answers, a supervisory relay Y responds, unlocks relay L, and earths the a-wire, causing a similar relay at the outgoing end of the junction to energize and initiate metering. If a busy condition is encountered, busy tone and flashing battery are connected in known manner to the outgoing a-wire, causing the intermittent response of relay Y, which repeats the signal over the junction a-wire. Delayed metering arrangements as described in Specification 200,928 are provided at the outgoing end of the junction to prevent the response of the supervisory relay thereat from causing the meter to be operated under these circumstances. When the calling party hangs up, release occurs in the usual manner, but if the called party clears, first relay Y relapses and lights the supervisory lamp PL.