GB371525A - Improvements in or relating to telephone systems - Google Patents

Abstract

371,525. Automatic exchange systems. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Feb. 23, 1931, No. 5681. Convention date, Feb. 22, 1930. [Class 40 (iv).] A common control circuit for a group of conversational switches is normally in operative association with an idle one of of the switches, and the switches remain in the position occupied when last used until thev are next taken for use by the control circuit. As described, a common control circuit for uni-directional group selectors is connected to an idle selector by a preselecting switch and comprises a register switch responding to incoming impulses, and an auxiliary switch responding to impulses sent by the group selector when it passes last contacts of groups, group selection being determined by a relay which operates when the register and auxiliary switches are in corresponding positions, said relay being also used to control the hunting movement. When first group selector IGW seizes group selector IIGW, relay V2 in the control circuit operates over the test wiper since P is energized over wiper a1 of the pre-selector a1 .. a8. The test circuit includes off-normal contacts of the register and auxiliary switches De, Dh. Relay C2 pulls up and A repeats impulses to register magnet De which holds V2, a circuit for the magnet D of the group selector being also completed over wiper a2, subsequent to the relapse of T1 which was operated by V2 and releases when De has taken two steps. When the group selector reaches last contacts of a group, contact is made at 15w, T2 operates to sent an impulse to magnet Dh of the auxiliary switch and to open the circuit of magnet D which is started off again at contact 41 dh of Dh. When wiper dh reaches a position corresponding to de, T1 operates over resistance Wi6 since V2 holds for a sufficient length of time after cessation of the impulse train. The circuit for D is opened and on the relapse of V2, T1 releases and the group selector hunts for an idle outlet. When an outlet is found T1 again operates, short-circuits P which short-circuits C2 so that C1 pulls up over (i), locks over (ii) and switches through. Release. On the relapse of C2, Dh and De home in succession, and Da hunts under the control of P for the next idle conversational switch. The conversational switch does not restore to normal until a homing circuit over 5w is completed on its next seizure by the preselector.