When a stem switch (8) is pulled out, a switch signal forming unit 9 outputs a signal (RS) indicating that effect, a control unit (13) receives the signal (RS) and starts clocking by a timer (13a). The control unit (13) receives a signal (HS) output from an electricity-generation detecting unit (12) within the clocking period, detects the electricity generating operation of an electricity generating unit (10), and outputs a signal (CS) indicating that effect. A narrow pulse forming unit (7) forms a narrow pulse having a width of such a degree that the motor (5) is not driven based on the signal (CS), and outputs the narrow pulse to a motor driving circuit (4). The motor driving circuit (4) flows a fine current through a coil (4a) which drives the motor (5) based on the narrow pulse. An external device detects a variation of the narrow pulse, thereby confirming whether electricity is generated.