Patent GB-191003-A (GB)
Abstract: 191,003. Siemens & Halske Akt.-Ges. Jan. 2, 1922, [Convention date]. Automatic exchange systems.-Means are provided for releasing a selector after a short interval in case the line relay fails to respond. The arrangement is described with reference to a group selector GW which, in the case of failure of the line relay, is raised one step and immediately released, the energization of the release magnet opening the incoming test circuit to release the preliminary selector VW. Selector. Upon extension of a subscriber's line from the line switch VW to a free group selector GW, the test circuit is completed through relays T, C and the contact 40 of the release magnet M, the relay T extending the speaking leads, the line relay A connecting up a slowacting relay V1 and the relay C operating a slowacting relay C1. The vertical magnet H operates in the usual manner on the receipt of impulses, the off normal contacts being closed at the first step, but the circuit of the rotary magnet D being broken by the energization of a relay V2. At the end of the vertical movement the rotary magnet is brought into action by the release of the relay V2. When an idle line is found, the test relay P is operated, stopping the hunting movement and extending the speaking leads to the connector LW. Connector. When the subscriber's dial is again operated, the impulses are repeated over the alead to the impulse relay A1 of the connector, energizing the vertical magnet HI intermittently, the relay B being operated throughout over the b-lead. At the end of the vertical movement, 'the relays A1, B release, energizing at the offnormal contact 24 the magnet S controlling the sida switch I-V, moving it to the 2nd position and bringing into action the rotary magnet D1. On release of the relays A1, B at the end of the rotary movement, the side switch is moved to the 3rd position, and thence automatically to its 4th position, the test relay P1 being connected up in passing and becoming locked up if the wanted line is idle. Supply of ringing current. The side switch, which in the 4th position gives a direct supply of ringing current, is moved by an interrupter 28 to its 5th position, in which ringing current is intermittently supplied through a cut-off relay U, which responds when the called subscriber answers and moves the side-switch to the 6th or talking position, in which the called line is fed with current through the relays A1, B. To prevent movement from the 6th to the 7th position on account of slow operation of the relay A1, the movement to the 7th position is also made dependent on the slow acting relay V. Release. When the called subscriber hangs up his receiver, the release of the relays A1, B moves the side switch to the 7th position, operating the release magnet M1, and upon closing of the off normal contact 37 the side switch is restored to the 1st position. When the calling subscriber hangs up his receiver, the de-energization of the line relay A releases the relay VI and operates the relay V2, releasing the test relay P and operating the release magnet M, which breaks the test circuit of the line switch. Release in case of failure of line relay. If in the establishment of a connection the line relay A fails to energize, the relays C, C1 operate to close the circuit of the relay V2, energizing the relay VI, which operates the vertical magnet H one step at the contact 8, whereupon the off-normal switch is operated, releasing the relay VI and operating the release magnet M. This action is normally prevented by the closing of the contact 6 before the slow acting relays C, C1 operate.