LINE CHANGEOVER DEVICE

PURPOSE: To avoid artificial mistake owing to line changeover device of a different communication system and to enhance the reliability by combining a timer and a monitor of a transmitter and switching the line automatically after awaiting stability of the transmitter just after application of power. CONSTITUTION: When a power supply monitor section 11 detects application of power, a timer 12 is operated and a line loopback section 13 loops back the line to disconnect a transmitter and a communication line. On the other hand, an alarm detection section 14 monitors the state of a multiplexer demultiplexer section 21 and line IFs 23, 24 and provides the output of an alarm signal in the case of a faulty clock or unestablished synchronization to suppress the changeover of a line changeover control section 15. In this case, a time for the transmitter 2 to be made stable is set to the timer 12 and the output of the alarm detection section 14 is suppressed and released after the lapse of a prescribed time to release the line changeover and line loopback. Thus, after the transmitter is made stable after application of power, the line is surely and automatically switched.