PURPOSE: To continue to send a power cut-off alarm for a constant time even at the time of the power cut-off.

CONSTITUTION: An alarm circuit 1 is constituted of a power cut-off detecting circuit 11 and an alarm transferring circuit 12, the power cut-off detecting circuit 11 has a function to monitor the condition of the power supplied to the circuit and the power outputs the presence of the cut-off to the alarm transferring circuit 12. The alarm transferring circuit 12 adds the additional information to send the alarm based on the information from the power cut-off detecting circuit 11, prepares the serial information to transfer the alarm and sends to an alarm transmission line. A power holding circuit 4 is a circuit to supply the power to the alarm circuit 1, is constituted of a secondary battery or a capacitor, usually supplies the power from a power circuit 3 to the alarm circuit l, and when an input power is cut off, supplies the power to the alarm circuit 1 only for the time necessary to send an alarm by the alarm circuit 1. An alarm circuit 2 has a function to send an alarm necessary for a system except the power cut-off and is not operated at the time of the power cut-off.