| 摘要 |
The circuit detects erroneous polarity in a 3-pole cord, thereby preventing damages to the electronic components, i.e., the damages caused by erroneous wiring. The circuit includes: photo- diodes connected between a neutral pin (1), a hot pin (2) and a ground pin (3) for emitting visible light during a half period of an ac wave; and photo-transistors for being driven by the visible light emitted by the photo-diodes. The output voltages of the photo-transistors are flattened, and then, are supplied as detecting voltages A), (B) and (C).
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