SIGNAL SENDING CIRCUIT OF A DISASTER PREVENTION SYSTEM.

摘要

A relay circuit (C1) in a disaster prevention system has a transmitter a receiver (Rx), a parallel-to-serial converter (62), a serial-to-parallel converter (63), a and a timer (TM). The transmitter sends a signal to a receiver terminal (10) when the timer is switched on. The timer is cleared off every time the relay receiver receives a correct signal from the transmitter. If the relay receiver fails, the timer keeps counting until a predetermined period of time (0.5 second) expires when the signal transmission is cut off. Thus the occupation of a signal line is prevented even if a failure occurs.