Patent GB-263306-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1925-12-19
Abstract: 263,306. Siemens Bros. & Co., Ltd., and patterson, W. G. Dec. 19, 1925. Automatic and semi-automatic exchange systems.-A repeater which repeats impulses in loop form and repeats backwardly the reversal of current due to the called subscriber's reply and other signals such as busy flash signals, comprises a ground-connected relay FH which is connected to the outgoing a-wire and which when energized connects a battery-connected relay D to the outgoing b-wire. On reversal of current in the junction both these relays are energized and energize a relay DL, with the result that the reversal is repeated on the incoming side, but in the case of busy-flash signals the junction b-wire remains connected to battery while the a-wire is connected alternately to battery and ground, so that relay FH but not D is energized. In this case relay FL is energized instead of DL to bring about the repetition of the signal. Each of the relays DL, FL when energized locks out the other. When a call is made to an operator the junction wires are both connected continuously to battery, with the result that the connection cannot be released until the subscriber and operator have both disconnected themselves. Normal operation. Relays A, AA are energized over the calling loop, relay FH and coil RA are connected to the outgoing a and b-wires, and relays LO and B are energized and lock themselves. At the first impulse the falling back of armature a1 energizes relay CA(1), which energizes relay CB which locks relay CA(2) and is kept energized over a<1>, b5, lo3, ca1. The impulses are repeated over contact a2 in a loop ca2, lo5. At the end of each digit the relays CB, CA relapse, the loop is broken, and the connections of relay FH and coil RA are restored. The called subscriber's reply reverses the battery and ground connections at the distant end of the junction so that relay FH is energized over the a-wire and connects the b-wire to relay D, which is also energized: Relay LO is unlocked and energizes relay DL (fl2, d4, fh3, b4, lo4) which locks itself under control of relay B. Relays D, DL energize relay CA(2), which energizes relay DA to reverse the connections of the relays A, AA to the incoming line. Relay CA, which is de-energized again by relay DA, momentarily short-circuits at ca2 the impulse contact a2, to prevent a false impulse due to the reversal, and connects a condenser across the incoming line to absorb the reversal click. Busy signals. The result of encountering busy conditions at any stage is to connect the distant end of the junction a-wire intermittently to battery instead of ground, so that relay FH is energized but not relay D, since the b-wire is also connected to battery. The unlocking of relay LO in this case energizes relay FL (dl2. d4, fh3, b4, lo4) which locks itself and connects the incoming a-wire through relay AA and armature fh4 to bat,- tery, thus repeating the signal. Since battery is now connected to both incoming line wires the relays A, AA relapse, but relay FH is kept connected to the outgoing a-wire over contact fl3 and connects the incoming a-wire alternately to battery and ground at fh4. Calls to operators. Connection to an operator's circuit results, upon the operator plugging in, in connection of battery to the a-side of the connection as well as to the b-side, so that relays FL and FH are energized. The relay B therefore remains locked and keeps the c-wire grounded until both the subscriber and operator have disconnected themselves.