A power-on signal detector (191) detects an output pattern of a control signal from a magnetic switch (180) while the power is off. When the output pattern is identical with an on pattern, the power-on signal detector (191) outputs a detection signal to a power supply control unit (170). When the output pattern is identical with an off pattern, the power-off signal detector (193) outputs a detection signal to the power supply control unit (170). the power supply control unit (170) switches between the state where a drive power from a power unit (160) is supplied and the state where the drive power from the power unit (160) is cut off.
