PURPOSE: To reduce manufacture cost by reducing the consumption and storage capacity of a battery, by disconnecting a battery support after the end of close operation.

CONSTITUTION: Once power supply 12 is turned OFF after the end of close operation or due to a fault of power supply 12 or power failure, power is supplied from battery 31 as a substitute for power supply 12, thereby starting battery support. By reading blank information in dynamic RAM14, decision circuit 21 decides on whether close operation has ended or not and when a decision on the end is made, FF24 is reset to reset to disconnect the battery support by relay circuit 25. In this way, the consumption of the battery is lessened and its capacity is reduced, thereby reducing manufacture cost.