Passive remote photoelectric surveillance alarm with telescopic optics
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United States of America Patent
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Sep 10, 1991
Grant Date -
N/A
app pub date -
Apr 3, 1990
filing date -
Apr 3, 1990
priority date (Note) -
Expired
status (Latency Note)
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Abstract
An intruder alarm includes a circuit with a photoresistive cell located in a housing with a piezoelectric crystal sound generator and battery to power the circuit and sound generator. A telescope concentrates light from a distance in a limited field of view upon the photoresistive cell to trigger the piezoelectric crystal sound generator when light intensity on the cell changes sufficiently from an ambient light intensity level.
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