GB561096A - Improvements in or relating to crossbar selector switching units - Google Patents

Abstract

561,096. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd., GILLINGS, C., and MURRAY, L. J. Jan. 8, 1943, No. 386. [Class 40 (iv)] In a system in which the outlets at a cross-bar group selector stage are tested by a common control circuit, the testing switch in the latter, instead of having separate leads to each of the (200) test wires as in the system described in Specification 560,732, has leads only to the (20) links of the cross-bar. When a selection is to be made, the prepare magnet of the wanted group is operated and then the hold magnets of all idle links. The common control switch then tests outlets in the wanted group over the crossbar contacts, the hold magnet of the selected outlet remaining energized and the remainder being released. Details operation. When the circuit shown is seized, the common control relays A, B, C, BB and the individual select relay 1GSP and relay 1GSR are operated as described in the prior Specification and the thousands digit is registered on switch TD which causes the operation of the corresponding select magnet such as 1GTP. In the present case, however, the relapse of C at the end of the digit energizes a relay NR which operates all the hold magnets such as 1GTH of idle link circuits. Switch OC then hunts under control of KR,<3> KRR over its bank 3 and contacts of the cross-bar switch for an idle outlet in the wanted direction and, when this is found, energizes over its bank 2 the corresponding hold magnet such as 1GSH at the incoming side of the selected link. This holds the outgoing hold magnet of this link, the others being released when NR is released by the relapse of N on the ensuing restoration of the switch TD.