Distribution system for telephone exchange - has control logic controlling one by one operation of terminal decoding and control circuits to ensure fault free signals

摘要

A distribution system for a centralised control such as a telephone exchange comprises a decoder (DC) to which the address code (AD) of a selected terminal circuit is applied. The decoder functioning is verified by a control circuit (C1) and the result from the control circuit is written in a first stage of a fault register (RF). The decoder delivers a row number to a first amplifier circuit (GAR) and the selection of an amplifier in the circuit is verified by a further control circuit (C2) whose output is written into a second stage of the register. The decoder also delivers a column number to a second amplifier circuit, this being verified by a further control circuit (C3) with the result written into the register. By verifying each stage of the operation as it occurs, a fault is immediately identified.