Patent GB-284333-A (GB)
Title: Improvements in automatic telephone systems
IPC: H04Q3/00
Filed: 1928-01-25
Abstract: 284,333. Siemens & Halske Akt.-Ges. Jan. 29, 1927, [Convention date]. Automatic exchange systems; metering.-A fleeting test of the wanted line is made in the interval between the successive relapses of two slow-release relays V2, U, and if the line is idle V2 is re-energized before U falls back and connects up ringing- current, the relapse of U a moment later putting V2 under control of a switch SS to ring every 3 seconds. The relay U, under the control of V2, acts also as a change-over relay. Group selector. Relays A1, C1 are energized, and the first digit is reward to vertical magnet H1 over V1, C1(10), A1(2), P1(13). The relay V1 is slow to release on account of its short-circuited upper winding, but falls back at the end of the digit and energizes the rotary magnet D1 over V1(16), A1(3), P1(1), and VI is then itself re-energized over Vl(15), D1(1) in series with H1, which is not energized since the switch has taken its first rotary step and the upper winding of V1 is no longer short-circuited at the rotary normal contact w1. The relay VI interrupts its own circuit and that of the magnet D1, so that rotation is continued until an idle connector is found, whereupon relay P1 is energized, locks itself over its upper winding, and switches through. Connector. Relay C2 is energized in the incoming test circuit. The next digit is repeated as positive impulses from A1(5) over the a-wire to relay A2 which repeats to the vertical magnet H2 over A2(22), V2, U(46), 2w2. The series relay V2 falls back at the end of the digit and energizes the slow-release relay U from an interrupter RU over C2(25), V2(51), in series with H2, which is not affected. The final digit is therefore repeated over U(47) to the rotary magnet D2. Relay V2 is again energized, and U (of which the original circuit is opened at the rotary normal contact 2w2) is held over V2(50) and U44. Busy test; supply of ringing current. At the end of the digit V2 and U fall back successively, and in the interval a circuit U(48), V2(53) is closed for the test rely P2. If the line is busy P2 is not energized and busy tone is sent back from SZ. If, however, the line is idle, P2 is energized, switches through, locks itself over its upper winding from C2(27), and (since U is for the moment still energized) closes a circuit for the lower winding of V2 from ground over U(50), Y(30), P2(39) to apply ringing current from WQ. A moment later U falls back and V2 is then intermittently energized over U(49) and a 3-second switch SS. In the first non-ringing interval after the called subscriber's reply, relays A2 and Y, which serve as feed relays for the called line, are energized and ringing is stopped. During conversation the b-line includes a condenser Co in the connector. The Specification as open to inspection under Sect. 91 (3) (a) describes the first-mentioned circuit of V2 as extending from ground over a, slow-speed interrupter to U(50). This subjectmatter does not appear in the Specification as accepted Release and metering. When the calling subscriber hangs up, relay A1 short-circuits C1 and a metering relay Z is energized over the b-wire in series with the upper winding of Y and contacts Y(31), P2(39). The relapse of C1 also shortcircuits P1, which closes a circuit for the rotary magnet D1 over P1 (13), C1(7), and the relay V1 interrupts this circuit to step the switch round until it passes out of the bank and is restored. In the connector the relay C2 falls back and releases P2, which is followed by A2 and Y, and the rotary magnet D2 is energized from RU until the switch is restored. If the called subscriber is the first to hang up, A2 falls back and closes at A2(21) a holding circuit from P2(39) for both windings of Y, so that release is delayed until the calling subscriber has disconnected himself and the call has been metered. Specifications 284,334 and 284,335 are referred to.