Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1985-11-22
1988-06-21
Orsino, Joseph A.
Communications: electrical
Condition responsive indicating system
Specific condition
250221, 250342, 250353, 340552, G08B 1318
Patent
active
047527684
ABSTRACT:
An apparatus for detecting intruders comprising a housing provided with at least one window, a passive infrared detector (for detecting the radiation emitted by an intruder around a wavelength .lambda..sub.1), and an anti-obscuring device (detecting by infrared radiation having a wavelength .lambda..sub.2 the presence of an obscuring of the appparatus for detecting intruders). The apparatus further includes an electronic circuit intended to operate an alarm when the presence of an intruder or an obscuring element has been detected. The apparatus for detecting intruders has a detector for detecting an obscuring element arranged at small and at large distances. It further includes a self-verification circuit. An obscuring element is detected, inter alia, by a mirror arranged at the end of the zone to be supervised, which returns radiation .lambda..sub.2 emitted by an emitter to a detector, both being situated very close to the detector of radiation having a wavelength .lambda..sub.1.
REFERENCES:
patent: 3858043 (1974-12-01), Sick et al.
patent: 4119949 (1978-10-01), Lindgren
patent: 4242669 (1980-12-01), Crick
patent: 4656462 (1987-04-01), Araki et al.
Hazan Jean-Pierre
Steers Michel
Briody Thomas A.
Haken Jack E.
Orsino Joseph A.
Tumm Brian R.
U.S. Philips Corp.
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