| 摘要 |
PURPOSE:To attain easy and sure fault check by bringing a detection circuit section into the state equivalent to the state that an object to be sensed comes in response to the check mode designation. CONSTITUTION:When a switch 32 of the mode designation section 30 is turned on or an L signal is impressed from an external terminal 31, the check mode designation is attained, a transistor (TR) Q41 is turned on and a node (a) goes to H. Then a TR Q42 is turned on, a TR Q42 is turned off to disconnect a parallel resistor R47, the adjusting resistor is increased, aud so long as no fault is caused, and the oscillation is stopped. A signal in response to the presence of the oscillation stop is outputted to a fault check output circuit 20 via a comparator 21, an integration circuit 22, a waveform shaping circuit 23 and a TR Q21 to check the presence of a fault of a detector for the proximity switch easily and surely.
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