GB1192500A - Improvements in or relating to Time-Division Multiplex Telecommunications Exchange Systems - Google Patents

Abstract

1,192,500. Automatic exchange systems. SIEMENS A.G. 23 Aug., 1968 [24 Aug., 1967], No. 40403/68. Heading H4K. Substations such as T1 to T256 are concentrated over a two-stage cross-point network RK giving access to terminals such as AL1 to AL48 multiplexed by gates ZS on to a time division highway MS, the crosspoint network RK having a route-finding network RKS. Call originations are detected by a scanner comprised of address register AG, decoder TSD, and line circuits B1 which pass a signal to supervisory highway MY if a looped condition is encountered. The scan halts on a calling condition until a connection has been set up over RK and loop supervision is transferred to a tdm terminal circuit AS1 to AS48, changes of loop condition from that point being signalled over supervisory bus YM synchronously with highway gating as controlled by circulating store U. A number of subscriber groups may be governed by the same control circuit, an address generator GG associating each group such as TG1 with the control circuit S over gate SI1 and highway MYR and associating the corresponding route-finding network RKS over a gate SI2. A call origination halts scanner address register AG and presents the calling line address to register AR from which it is indicated, by way of decoder DB, which one of the 16, 16 x 6 first stage switches of RK serves the calling subscriber. Each first stage switch has a link to each of the 6, 16 x 8 second stage switches. A decoder BD marks one of six wires in turn indicative of a particular second stage switch. A decoder AD for each setting of decoder BD marks each of eight wires in turn corresponding to each of the eight outlets of each second stage switch. For each of the 16 outlets of decoder DB an array of six diode/relay contact cross-points connect the outlet to gates G1 to G6 if the corresponding interstage links are free. Similarly for each of the 8 outlets of decoder AD an array of six diode/relay contact cross-points connect the outlet to gates 1G to 6G if the corresponding outlet of any one of the second stage switches is free. The outputs of gates G1 to G6 and 1G to 6G are oommoned and taken as inputs to an AND gate GI. Thus for a given setting of BD indicating a particular second stage switch, if the corresponding gates Gn, nG both open, a free outlet from the second stage switch exists and a free link gives access to the switch from the first stage switch of the calling sub-station, gate GI opening to pass the identity of the accessible outlet to control S and thence to the register AR which sets up the connection across network RK. Call terminations are effected in the same fashion by supplying AR with the called sub-station identity. In searching for a free path the scanner decoder BD may cycle over all its outlets for each set of the decoder AD. The outlets of decoder AD may be employed to mark the sets of AND gates direct, in the fashion of BD as shown, while BD scans the gates over idle/busy contacts in the fashion of AD as shown.