Patent GB-329024-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04Q3/00
Filed: 1929-02-12
Abstract: 329,024. Automatic Telephone Manufacturing Co., Ltd., Taylor, R., and Beale, C. E. Feb. 12, 1929. Automatic and semi - automatic exchange systems.-In an incoming selector-repeater operated by impulses over the junction conductors in parallel, a speaking connection is completed when the called party replies or when a busy condition is encountered at a succeeding switch, the connection being open while the succeeding switch is being operated. The impulse circuit includes the windings of a differential relay I at the outgoing repeater, Fig. 1, and this relay operates in response to the replv of the called party or to the busy signal to effect the repetition of the corresponding backward signal. The outgoing repeater may, if a busy condition is encountered, hold any operated succeeding switches until the calling party or operator restores. On seizure of the repeater, Fig. 1, impulse relay A operates and energizes release relay B, busy control relay BC, and a relay CR which short-circuits a winding to make it slow to release. Parallel circuits from battery over resistance 34 now extend over the windings of relay I, the outgoing conductors 26, 31, to ground over the windings of relay A2 at the incoming selector-repeater, Fig. 2. Relay I remains inert as its windings oppose each other, but relay A2 operates B2, and impulses repeated by A at 22 are repeated by A2 to the vertical magnet V and change-over relay C. Stepping relay G operates over N, 42, 41, 40, holds over the springs 44 of rotary magnet R, and operates CB. When C falls back at the end of the impulse train, R operates and interacts with G to step the switch, G being re-operated over N, 44, 48, 47 to ground on busy lines. When an idle line is found, switching relay H energizes and a loop over 51, 12, D2 is connected up to the windings of the impulse relay at the succeeding switch. Relay 12 operates and holds CB, and A2 repeats subsequent impulse trains at 51. When the connection has been completed, reversal of current on reply of the called subscriber operates polarized relay D2 so that AD operates over 57, 56, 40, locks over 58, 47, 46, and completes the speaking circuit and disconnects relay A2 which releases B2. At the repeater, Fig. 1, relay I operates since its windings are connected in series to battery and ground at the final selector. Relay IA energizes over 59, 17, locks over its light armature 61, and completes a loop D, 23, 22, 21, I across the outgoing junction, in which D pulls up and I remains operated. Relay DA reverses the current over the calling loop, and relay CR releases, but during its release period holds a high-resistance loop 63, 64, 65 across the loop to reduce clicks in the subscriber's receiver due to the reversal of current. Relay BC remains held over 66, 60, 59, 17. Busy signals; holding distant switches operated. If the wanted line is busy, battery flash is connected up at the final selector and releases 12 and therefore CB. Relay AD operates over 57, 67, 40 and switches through as before, so that at the conclusion of the flash period relays I, IA, Fig. 1, operate and function as previously described. At the next flash period relay I falls back and releases BC so that when I re-energizes at its conclusion BR energizes over 66, 60, 59, 17, locks up and connects up busy flash from conductor 69 to operate relay A intermittently, whereby the signal is repeated to the calling loop. Relay B is held over its lower winding during flash periods. If it is desired to hold the distant switches during the repetition of the busy signal, terminals 71, 72, Fig. 1, are strapped together so that relay BR completes a loop across the outgoing wires. If all outlets of the selector repeater are busy, relay CS operates over eleventh step springs S, short-circuits relay H, and at 73, 28 completes the busy flash circuit over relay A2. The repeater, Fig. 1, responds as before.