Telephone exchange coupling field control matrix - has relays at intersections of row and column conductors and supervising and testing ccts.

摘要

The matrix has row and column conductors corresponding respectively to the inputs and outputs of the coupling field, so that the latter can be interconnected by operating the relay at each intersection of the appropriate row and column conductors. The matrix has a supervising circuit which detects a short circuit between the row or column conductors, or the failure of one or more of the coupling relays, associated with a testing circuit, for localising the fault. The testing circuit employs a current measuring network and is connected to the row and column conductors individually by operating an appropriate series contact, the series contacts for the remaining conductors being open.