Passive infrared alarm device

Details Passive infrared alarm device Passive infrared alarm device

1978-07-13

1981-01-13

Caldwell, Sr., John W.

Communications: electrical

Condition responsive indicating system

Specific condition

250352, 250510, 350 16, 350290, G08B 1318, G02B 520

Patent

active

042452171

ABSTRACT:
A passive infrared alarm device evaluates the changes in infrared radiation level of a monitored room or a monitored portion of a room for alarm purposes. In accordance with the invention, an infrared sensing element is employed toward which an optical reflector directs infrared radiation emanating from one or more angles in a room to be monitored. An infrared filter is mounted in the path of the reflected infrared radiation before such radiation reaches the sensing element. The infrared filter is designed to absorb infrared radiation below a predetermined minimum wavelength, and additional means is provided for partially absorbing infrared radiation below the predetermined minimum at the reflector.

REFERENCES:
patent: Re29082 (1976-12-01), Schwarz
patent: 3473864 (1969-10-01), Garbuny
patent: 3766080 (1973-10-01), Swinehart et al.
patent: 4087689 (1978-05-01), Asawa

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