| 摘要 |
PROBLEM TO BE SOLVED: To enable a cooling fan, that sends air flow to a printed circuit board, to be properly controlled in rotation at a low cost. SOLUTION: Contact points 10 and 11, a series circuit composed of a light emitting diode 12 and one region 13b of a variable resistor 13, and a power loss detection circuit composed of a contact point 8 and a low resistor 9 which are connected in parallel are provided between a printed board 2 and a P electrode of a direct current power supply, and the other region 13c of the variable resistor 13 is inserted in a power supply circuit of a motor 5a. When the power loss of the printed board 2 is detected, the contact points 10 and 11 are closed and the contact point 8 is opened, a movable contact 13a of the variable resistor 13 is moved until the light emitting diode 12 starts emitting light, the contact points 10 and 11 are opened and in this state, the contact point 8 is closed to put the printed board in a normal operation state.
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