| 摘要 |
PURPOSE:To prevent a trouble from being caused when a power supply is connected to a polar signal line by judging the polarity on the side of the power supply by a microcomputer and, when a disagreement is present in polarities, closing a switch after operating a polarity inverting relay. CONSTITUTION:The input port P3 of a microcomputer 1 is connected to the side of a power supply and the polarity of a power supply line is judged. When the polarity disagrees with that of one of two polar signal lines 2, the microcomputer 1 outputs signals from an output port P1 to excite a relay coil X1 and changeovers relay contacts X1-1 and X1-2. Then the polarities are again judged and, when an agreement is obtained, signals are outputted from an output port P2 to turn on a transistor Q1, thus connecting the power supply to the polar signal lines 2.
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