| 摘要 |
<p>A contactless motion detector, including an oscillator and an amplifier, has an energizing circuit connected across a Zener diode in a section of a voltage divider also comprising a current-sensing resistor, another section of this divider comprising an output thyristor in parallel with a resistive branch which may be a constant-current unit. The voltage divider receives pulsating direct current from a supply circuit including a load; an ancillary thyristor has its gate and cathode connected across the current-sensing resistor so as to fire when the load current exceeds a certain limit, the two thyristors being so coupled to each other that conduction of the ancillary thyristor cuts off the output thyristor. Normally, the output thyristor is controlled by a switching transistor responding to an output signal from the motion detector; the ancillary thyristor, when conducting, may directly lower the gate potential of the output thyristor or may remove normal operating potential from a deactivating input of the detector to disable a switching transistor which controls the output thyristor in response to an output signal from the detector.</p> |
