| 摘要 |
PURPOSE:To provide a passive infrared human body detector which can immediately and automatically detect an 'interrupting action' which makes the human body detecting function of the detector incompetent by intercepting the light from a detecting area to a PIR sensor with a light shielding material when the action occurs. CONSTITUTION:A light emitting means 7, reflecting mirror 10, and such a discriminating means as the comparator, etc., which discriminates that the electric output of a light receiving element 9 is increased or decreased from that at ordinary time are provided at both ends of a shielding material detecting optical path crossing the front face of a light receiving window 3.
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