STD telephone exchange - has timing stage triggering alarm if not reset within given time due to fault in selection processes

摘要

The telephone exchange has each connection request issued by the request line from a register passed as control pulse to an output line shared by all groups of registers. A timing stage is started when the selector starts. This timing stage is reset at the end of each selection cycle and also by the control signal. The control signal prevents the timing stage being started for as long as it persists. The stage initiates the release of a fault/error message if it is not reset within a given time.