PURPOSE: To restrain a rush current to a condenser and to shorten a charging time by providing an electric current restriction circuit and a DC-DC converter between a signal processing part to process a multiple signal containing a control pulse and a lock drive voltage and a large capacity condenser for lock solenoid drive.

CONSTITUTION: An electric current restriction circuit 2 and a DC-DC converter 3 are provided between a signal processing part 1 and a large capacity condenser C. Then, the condenser C is charged by a constant current by way of a booster effect of the DC-DC converter 3. Consequently, it is possible to prevent generation of a rush current at the time of starting charge to the condenser C, and additionally, it is possible to shorten a charging time of the condenser C.