Patent GB-257302-A (GB)
Title: Improvements relating to telephone systems
IPC: H04M3/12
Filed: 1925-03-27
Abstract: 257,302. Siemens Bros. & Co., Ltd., and Rousseau, E. J., C. March 27, 1925. Automatic exchange systems.-An inter-office. trunk is tested for faults on seizure and if faulty is marked permanently busy and shows a lamp signal. This busy mark is in some cases delayed until a short time after the trunk has been released to ensure release of the preceding switches. When the fault is cleared the trunk is automatically restored to normal. Arrangements are described in which (1) the trunk is seized by a first selector which repeats the remaining digits over one wire, (2) the trunk is seized by a first code selector and the remaining digits are sent over both wires, (3) the trunk is seized by an intermediate selector held from ground at the first selector and the busy mark is delayed until the trunk has been released, (4) the testing arrangement is included in an outgoing repeater. First arrangement, Figs. 1 and 3. The selector operates in known manner to select an idle trunk, and switching relay T pulls up in series with relay JA which connects battery to the b-wire. If the trunk is non-faulty, the line and release relays A, V at the incoming end energize relay JB over the a-wire in series with relay JC which does not pull up on this circuit. When the trunk is released, relays JA, JB fall back. If the trunk is short-circuited, relay JA energizes relays JB, JC in series, relay JB being released immediately by relay JC. If the trunk is open, relay JB is not operated at all. In either case relay JA remains locked up until the fault is cleared over ja4, jb4 and keeps the lamp PL alight and a busy ground on the c-terminal. The condition of the trunk is tested at will by means of a non-locking, key K. In case it is not neccessary to test for a short circuit, relay JC is omitted. Second arrangement. A first code selector, Fig. 4, selects a trunk, Fig. 1, in which the testing arrangements are similar to those shown in Fig. 3. Owing to the different arrangement of the line relay A at the incoming end however, relay JC is unnecessary and relay JB is connected between the two wires of the trunk. Third arrangement, Figs. 7 and 8. The selector shown may be picked up by that shown in Fig. 4. Line and release relays A, B pull up, the digit is repeated to magnet VM through series relay C and vertical springs k<1> - - k<3> change over. The relapse of relay C cuts off relay A to energize the rotary magnet RM. At the end of the stroke rm connects winding 2 of relay A, which now acts as a stepping relay, to the test wiper. When relay T switches through, relays A, B fall back permanently. The selector is held by ground at the first selector over the c-wire, which is extended to the seized trunk. Consequently a faulty trunk must not have its c-terminal permanently grounded until it has been released by the switches. When the trunk is seized, relays JA, JD pull up over the loop energizing relay JC to connect relay JB (1) across the trunk. If it is non-faulty relay JB locks up and releases the other relays. If it is faulty, relays JD, JC are locked up. When the connection is released relay JS is unlocked but holds for a short time owing to a copper sleeve. When it falls back, ground from jc4 is connected to the c-terminal. The key K controls only relay JC. Fourth arrangement. The selector, Fig. 4, may seize a repeater, Fig. 5, in which relays A, G pull up and connect relays E, D across the trunk. If it is in order, relay E short-circuits a resistance in the impulsing circuit, energizes relay B, and releases relay G. Impulses are repeated at a<2>, the first impulse energizing relay C to put a low impedance bridge across the trunk and short-circuit relay E. Between trains relay C falls back and relay E is re-energized. If the trunk is faulty, relay G is unable to ener. gize relay E, relay B does not pull up, and relay G remains locked up over e<3>, busying the line and lighting lamp PL. Busy signalling arrangements; statistical metering. Busy flash signals are repeated back over the repeater, Fig. 5, by relay F, which pulls up at each relapse of relay E. If the selector, Fig. 7, is unsuccessful, 11th terminal springs w1 - - w3 energize relay T, ground wiper C<0> to operate a meter, and energize relay C. Relay A is re-connected to the talking wires and busy tone and flash are connected to its ground end, the release relay B being held up by synchronous impulses from LF over its winding 2. Alarm arrangements. The selector, Fig. 1, has a lamp PL controlled by off-normal relay L and the supervisory relay Y. The selector, Fig. 7, has a lamp PL controlled by the line relay. Metering systems.-Delayed metering arrange. ments similar to those described in Specification 200,928 are provided in the selector, Fig. 1. The Answering relay Y unlocks off-normal relay L and causes the next closure of springs 11, 12 to energize relay S. which locks up. The subsequent closure of springs 11, 13 energizes relay Z which locks up to y2, unlocks relay S, and completes the metering circuit z1, s1