Passive infrared intruder detection system
First Claim
1. Radiation detection apparatus, comprising(a) first detector means (6-9) for detecting radiation of a first wavelength emitted by a radiation source;
- (b) indicating means (10) connected with said first detector means and operable when the detected radiation exceeds a first level; and
(c) reflection-responsive means operable when an obturating element (11) is positioned between the radiation source and said first detector means, said second indicating means including(1) transmitter means (14) adjacent said first detector means for transmitting a signal of a second wavelength in the general direction of the radiation source; and
(2) second detector means (15-17) adjacent said first detector means for detecting the signal of second wavelength when reflected from said obturating element (11) for operating an indicating means when the level of the reflected signal received by said second detector means exceeds a second level.
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Abstract
Radiation detection apparatus is disclosed including a first detector (6) for detecting radiation at a wavelength which is preferably in the infra-red region, and a device for sensing the presence of an obturating element (11), which element acts to prevent operation of the first detector. The sensing means includes a transmitter (14) which transmits a signal at a second wavelength, and a second detector (15) responsive to and arranged to receive the signal in the presence of the obturating element, preferably by reflection of the signal from the element. An alarm (10) may be activated in response to detection of radiation or of the transmitted signal.
43 Citations
9 Claims
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1. Radiation detection apparatus, comprising
(a) first detector means (6-9) for detecting radiation of a first wavelength emitted by a radiation source; -
(b) indicating means (10) connected with said first detector means and operable when the detected radiation exceeds a first level; and (c) reflection-responsive means operable when an obturating element (11) is positioned between the radiation source and said first detector means, said second indicating means including (1) transmitter means (14) adjacent said first detector means for transmitting a signal of a second wavelength in the general direction of the radiation source; and (2) second detector means (15-17) adjacent said first detector means for detecting the signal of second wavelength when reflected from said obturating element (11) for operating an indicating means when the level of the reflected signal received by said second detector means exceeds a second level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification