GB256322A - Improved circuit arrangements for automatic switches used in telephone systems - Google Patents

Abstract

256,322. Siemens Bros. &. Co., Ltd., and Patterson, W. G. May 6, 1925. Automatic exchange systems. - Automatichunting in a numerical or non-numerical switch is effected by interaction between the stepping magnet and the test and switching relay. The latter, which thus acts also as a stepping relay, is provided with two or three windings, one of which is intermittently energized during hunting and operates the relay partially so as to control only the stepping-magnet circuit whilst the other winding or windings are energized, when an idle trunk is reached and operate the relay completely to stop the hunting operation. Non-numerical selector, Fig. 1. The line relay R completes a circuit r2, t4 for the rotary magnet RM which operates. At the end of its stroke the magnet armature rw completes a circuit for winding I of test relay T, which operates only its contact t4 to break the magnet circuit. If the first trunk is busy the relapse of armature rm causes the release of relay T which thus re-closes the magnet circuit. Hunting continues until an idle trunk is found when relay T remains operated over its windings 2. 3 and contacts r1, rm, r2 as soon as the magnet RM falls back. The. test relay now operates all its contacts and remains locked over contact t1 and off-normal wiper D‹. For an incoming call, the test circuit includes wipers C‹. D‹ in their normal positions and windings 2 and 3 of the test relay which operates fully. Group selector, Fig. 2. Relay A energizes over the b wire from battery at a preceding feed bridge and operates change-over relay D. Impulses are repeated by relay A over contacts t5, d2, a1 to the vertical magnet VM and at the conclusion of the digit the relapse of relay D completes a circuit t5, a4, rm, k4, for winding I of the test relay T which operates partially to close at its contact t6 a circuit for the rotary magnet RM. The magnet rotates the wipers and opens the circuit of relay T which, if the first trunk is busy, releases and, in turn, opens the magnet circuit. The relapse of the magnet re-energizes relay T and hunting continues until an idle trunk is reached when relay T remains operated over its winding 2, contact a2, and earth on the incoming test wire c and operates all its contacts, thus permanently breaking the hunting circuit at contact t5. Relay T remains locked over its winding I and the incoming test wire.