Patent GB-325830-A (GB)
Title: Improvements in or relating to automatic and semi-automatic telephone exchange systems and apparatus therefor
IPC: H04Q3/00
Filed: 1928-11-28
Abstract: 325,830. Standard Telephones & Cables, Ltd., and Wright, E. P. G. Nov. 28, 1928. Automatic exchange systems.-Connection to a wanted line is established by two or more permanently associated non- homing single - motion switches, A, B, one of which has an outlet associated with the wipers of the second. 'The switches A, B hunt for a line marked by a pilot switch Y or Z, one of which has hunted for a free line in a. group on which selectable potential has been placed By a numerical switch X. The switch B hunts singly if the called line is served by it directly ; otherwise the switches A, B hunt together. The system is of the type using bye-pass control circuits (shown below the chain line). Specification 324,982 is referred to. Setting of control switches. The selector with its associated control circuit is tested through the wire T to battery at b4 (tt4, p2, e9, X10, YC, ZC) and the circuit is switched through over BP+, BP- operating relays A, B, M. The digit is repeated by A to R1 and steps the wipers X1 - - X10. At the first step M releases. Relay C operates in series with R1 and enables R2 to step its wirers YC, YM, &c. off normal (R2, c2, b1) and when M releases R2 steps until M re-operates which occurs when wiper YC reaches the terminal corresponding to the first line of the group marked by R1. The switch R2 (Y wipers) serves certain groups of outlets and the switch R3 (Z wipers) serves other groups, according to the setting of the switch R1. When R1 is set to any position corresponding to a group served by R3, relay D is operated over bank X10 stopping R2 and allowing R3 to step until M operates over ZC. When the impulse train ceases, C releases and when M has operated E pulls up allowing R2 or R3 to recommence stepping. The relays P and Q are connected to wipers YT or ZT dependent on whether R2 or R3 is searching, and when a free circuit is reached one or both these relays will operate breaking the stepping circuit of R2 and R3. If P operates relay H pulls up and if Q pulls up J and H are energized. If all outlets are engaged the switch R2 or R3 steps to the last contact of the group and M operates (e10, b1) closing the circuit for G to connect busy tone. Setting of conversation switches. When E pulled up the circuit for R1 was recompleted and this switch steps until its wiper X3 connects to the selected inlet over TH when relay T operates, stopping R1 and operating TT, replacing the bye-pass circuit BP, releasing the previous control circuit by removal of earth from wire T and returning guarding earth from b1 over TH. Relay TT also completes the circuit for SB (prepared by relay H when R2 or R3 had found a free outlet) and, if D has not operated, for SA. If D has operated the circuit will be extended by switch B and in this case SB steps the switch until F operates (d18, h16, ZM1 or 2 and multiple wiring to BM and X10 to earth at tt5) when HS operates to switch the circuit through. If D has not pulled up switch A is stepped by SA until it reaches the marked line when M operates over YM and AM and switch B steps until it reaches contacts connected to the wipers of switch A when F operates. When both M and F have pulled up, HS operates and switches through as before. Release. When relay H pulled up A releases followed by B, but E and T are held over the test circuit YT or ZT by earth from the succeeding selector. When this is removed E and T release followed by MH and TT. Switches R1, R2 and R3 return to normal and then battery is reconnected to the test wire over YC and ZC. Spark-quenching circuits are connected to R1, R2 and R3 and common spark-quenching circuits are multipled to all the SA and SB magnets.