If a power supply is provided to a circuit necessary to control a switch for switching a path after wakeup, or if a buckle switch is switched while a microcomputer is asleep, an electrical current necessary for reliable operation of the buckle switch cannot be supplied during sleep, so that the buckle switch will not operate normally. This creates the possibility that wakeup cannot be performed. To permit the electrical current necessary for reliable operation of the buckle switch to be secured if the buckle switch is switched while the microcomputer is asleep, an FET capable of being kept ON or OFF by a power supply acting during sleep, a resistor connected with the FET, and a resistor of large resistance for blocking excessive dark current if the buckle switch is connected are arranged in parallel. The combined resistance of the parallel combination of these elements is used as a pull-up resistance at the input of a control unit.