Patent GB-915971-A (GB)
Title: Improvements in or relating to circuit arrangements utilising crossbar switches
Inventor: DENBY JAMES FREDERICK
IPC: H04Q3/00
Filed: 1958-12-18
Abstract: 915,971. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Nov. 30, 1959 [Dec. 18, 1958], No. 40877/58. Class 40 (4). A cross-bar switch has a plurality of inlets 1RS1-1RS10 (Fig. 1), each multipled to moving contact members of corresponding cross-points of a plurality of bridges 1BM-5BM and a plurality of outlets R1-R10, each individually terminated upon the moving contact members of another cross-point of one of these bridges so that a connection from any of the inlets to any of the outlets terminated on a particular bridge may be established over the one set of bridge commons of that bridge. As shown, each inlet is associated with one of the select magnets 1SM-10SM of the 12 x 10 switch and each outlet with one of the auxiliary magnets 1AM, 2AM. Second groups of inlets 1RS11- 1RS20 and outlets R11-R20 are also provided. Register-connector (Figs. 2, 3).-Of the twenty incoming relay sets served only 1RS1 is shown and this, like relay sets 1RS2 to 1RS10, is multipled over the first five bridges BR1 to BR5 of the register-connector RC. Two of the twelve cross-points of bridge BR1 are shown, the upper one controlled by 1SM being associated with 1RS1 and the lower, controlled by 1AM, with register R1. A by-path control circuit, such as BPC1, serves for each register appearance on the cross-bar switch. Three electronic high-speed hunting circuits, preferably of the type described in Specification 765,929, are provided; one 1RSH having twenty stages, one per incoming relay set, and the other two RH1, RH2 each having ten stages, the stages of the former being individually associated with the registers R1 to R 10 and by-path control circuits BPC1 to BPC10 and those of the latter with R11 to R20 and BPC11 to BPC20. A single multi-conductor by-path BP is used in setting up each connection to establish a " pre-dialling " path to the register pending operation of the cross-bar switch, and for transmitting class-of-service signals between the incoming relay set and the register. On seizure of 1RS1 the operation of relay A applies H.T. to lead MK in the relevant stage S1-S20 of the hunter 1RSH, and to the common start lead ST of that hunter and to lead M of each of the stages of RH1 and RH2. Idle registers are indicated by H.T. on the leads MF of the corresponding stages of BH1 and RH2, which stages are conditioned by the marking of their M leads preparatory to possible seizure of a register. Hunter 1RSH hunts stage-by-stage for the first marked stage, in this case S1, and the SZA lead of that stage is marked, thus energizing the start lead ST of hunter RH1. RH1 hunts for the first free register, say R1 and a pulse is produced on lead SZ of the corresponding stage, S1, to operate relay BP in the circuit BPC1. Lead SZ also extends to a conductor common to all stages of RH1 leading to the SZB leads of the first ten stages of 1RSH. The operated stage S1 responds, producing a positive potential on its lead OR to operate 1BP in the calling relay set 1BS1. In the circuit 1BPC operation of BP operates 1AM and relay CS and removes the free potential from stage S1 of RH1; while in the relay set 1RS1 operation of 1BP diverts the incoming loop from the A relay to the + and - conductors of bridge BR1 and over the by-path to relay AA in the register, holds A in a local circuit, connects H.T. to the class-of-service terminals COS1, COS2 which are extended to the relevant two of the terminals V to Z, and thence to the register, disconnects the demand lead for the hunting circuits, and operates 1SM. With 1AM and 1SM operated ground is extended over contacts 1AMC and 1SMC to a common operating lead and thence over front BP to operate the bridge magnet 1BM. In the meantime, AA has pulled up to the loop extended over the by-path, and fired VK1, whereupon B operates. AA repeats incoming dialled digits to storage means in the register. Each release of AA extends H.T. to the trigger of VK2 but the time constant of 1R1, 1C1 prevents firing during the impulse trains. Operation of 1BM completes a circuit over lead REL to effect resetting of the hunting circuits, whereafter BP is released, and effects the closure of the two cross-points to complete the relay set/register connection. In the relay set Z operates, holds over its second winding, releases 1SM, and disconnects the by-path. The release of BP deenergizes 1AM and CS. The register initiates its own release, a switch-through signal over lead OP effecting the disconnection of H.T. from 1BP, the release of which switches through to the first selector 1S Z is held, AA releases and VK2 fires, whereupon VK1 is doused, thus releasing B and 1BM in turn, whereafter VK2 is doused.