Patent GB-303930-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1927-10-14
Abstract: 303,930. Automatic Telephone Manufacturing Co., . Ltd., and Flenley, A. E. Oct. 14, 1927. Addition to 241,287. Automatic exchange systems. - In the system described in the parent Specification wherein private branch exchanges are reached over a group selector which seizes a relay group containing battery feed, ringing and supervisory arrangements. and associated with a number of non-numerical switches, the switches are arranged to hunt simultane sly instead of in succession. The switches step synchronously and test simultaneously, The system described comprises two switches RS1, RS2 onnected repectively to the odd and even lines of a P.B.X., the test relays having different operating lines to give preference to one switch when idle lines are encountered simultaneously. For testing, a circuit is completed over a jack to give a signal indicating which switch has made the connection. On seizure of the relay group, line relay A and release relay B operate and the first impulse of the final digit energizes a starting relay HS which short-circuits a second winding to make it slow to release. Shunt field stepping relay G now operates with its winding in parallel over springs 38, 39. contacts 31 to 33 and 8, and wipers 43, 47. to complete the circuits of the magnets DM1, DM2. When wipers 43, 47 leave the home position. HS relapses and changes over the circuits of relay G to the test wipers 40, 44, and both switches hunt until one or both find an idle line. If one finds an idle line, the corresponding test relay HA or HB connects one test wiper 40 or 44 to the. upper winding of switching relay H, prepares the circuits of the line wipers 41, 42 or 45, 46, and disconnects the other test relay and wiper. HA is arranged to operate more quickly than HB so that if idle lines are encountered simultaneously. HA operates and disconnects HB. Switching relay H locks up over its lower winding and short-circuits its upper winding to place full ground from 10 on the test wiper. Supply and control of ringing current. Relay H completes the ringing circuit (battery 7, 15, 23 or 28, P.B.X. line, 21 or 26, 12, 5, 16, upper winding of F and conductor 53) and a ringing signal is sent back from the circuit over condenser 54 to the called party. The energization of ringing trip relay F when called party replies extends his loop to the back bridge reversing relay D. Release When calling party hangs up, the operated relays release and relay HS operates over the wipers 43, 47 to ground the guard wire 48 at 30 and extends ground from the wipers 43, 47 over the windings of stepping relay to home the switches. Busy signalling arrangements; statistical metering. If all P.B.X. lines are busy, the wipers move on to last terminals of the banks. Test relay HA operates to complete a circuit over wiper 40 for the busy relay GA which operates traffic meter ME and at 17 substitutes busy tone and flash conductor 52 for ground on the lower winding of line relay A. Release relay B is held during flash periods by battery over conductor 51 and a second winding of B to ground at 18. Testing arrangements. If switch RS2 makes the connection during .a test, relay HB completes a circuit for a buzzer 55 over test-jack springs T, contacts 22 and 10, but if RS1 makes the connection the buzzer remains silent. The switches are provided with pointers so that the number of the seized line can then be ascertained.