PURPOSE: To reduce the number of part items and simplify a signal processing system by enabling alarms outputting alarm to be also used for display of trouble of an electric lock.

CONSTITUTION: Alarms 19, 20 giving the alarm when a transmitting signal is an unsuitable optical signal, are served in addition as alarm units 19, 20 giving the alarm at the trouble of an electric lock. A means is provided, which continues a trouble alarm by the alarm unit 20 giving the alarm for the trouble of the electric lock, and stops a crime prevention alarm in the case of an unsuitable transmitting signal after a prescribed time so as to return the unit in the initial condition. A reset switch 21 is provided, which stops a trouble alarm by the alarm uits 19, 20.