Fire and intruder detection and alarm apparatus

Communications: electrical – Systems – Call station

Patent

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Details

340228R, 340258R, 340420, G08B 2100

Patent

active

040527166

ABSTRACT:
Improved apparatus is provided for monitoring a space under surveillance, for detecting the existence of a fire, the presence of an intruder or the occurrence of other abnormal conditions, and for providing a warning signal for actuating an alarm or the like in response thereto. The apparatus employs a plurality of sensors which respond by changes in the electrical characteristics thereof to the level of infrared, light or other radiations from the monitored space respectively sensed thereby. The apparatus significantly provides means for rendering the individual sensors directionally responsive to radiations from respectively corresponding portions of the space being monitored, for employing such sensors as output-affecting elements in more than a single arm of an electrical bridge circuit, for employing such sensors when desired in a plurality of operationally related electrical bridge circuits, for employing capacitative coupling between the output of a sensor-controlled bridge circuit and a differential amplifier to "mask" very slow changes in the output of the bridge circuit due to normal ambient variations while retaining high sensitivity in responding to more rapid changes of such output typical of fire, intruder or other abnormal conditions requiring alarm actuation, for employing such differential amplifier for converting changes in capacitatively coupled output from a sensor-controlled bridge circuit into direct current signals of polarity dependent upon the direction of change in such bridge circuit output, and for employing bridge type rectification for converting signals of either polarity from such differential amplifier into control signals of a single polarity for actuating an alarm activating switching component.

REFERENCES:
patent: 2871466 (1959-01-01), Vassil
patent: 3117311 (1964-01-01), LeMaire
patent: 3191068 (1965-06-01), Robb
patent: 3494196 (1970-02-01), Moussette
patent: 3636540 (1972-01-01), Harris
patent: 3725660 (1973-04-01), Doherty
patent: 3737886 (1973-06-01), Dinges

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