Telephone exchange with switching equipment in groups - has common control and monitoring circuit for each rack switched via AND logic from lines

摘要

A telephone exchange switching circuit has switching equipment connected in groups. The groups are allocated their own control equipment. There are sets of lines individually connected to control equipment related to a particular group. The control equipment is used to record, and process dialling instructions for establishing or monitoring calls. Each exchange assembly (L) has its own monitoring circuit (S). The monitoring element can be switched to either of two positions. This occurs when two control signals appear simultaneously, where one denotes that the transmitting control line is in the clear operating condition. The second represents successful recording of a characteristic signal derived from the control unit (P).