| 摘要 |
PURPOSE:To detect the presence/absence of a disconnection in a detection coil with a high frequency oscillating type contactless switch composed of a DC bias circuit and the detection coil, which are connected in series, by detecting a DC bias voltage. CONSTITUTION:When a detection coil L1 is not disconnected, oscillating AC components around a voltage VB are overlayed around the base of a transistor Q3 one upon another, because the DC bias voltage of the transistor Q3 is the voltage component BB of a bias circuit 3. On the other hand, when the detection coil L1 is disconnected, no electric current flows to the bias circuit 3 and oscillation is stopped. Therefore, when the voltage shown on the B side of the figure is inputted to a detection circuit 9, the voltage exceeds a level discriminating value La. As a result, an integrated output, namely, the output (iii) of the detection circuit 9 rises to a prescribed value and is saturated and the output (iv) of a voltage discriminating circuit 10 becomes 'H' in level, and then, an 'H' level signal indicating a fault is outputted from a fault output circuit 11.
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