Optical smoke detector

Details Optical smoke detector Optical smoke detector

1979-05-18

1981-02-03

Caldwell, Sr., John W.

Communications: electrical

Condition responsive indicating system

Specific condition

250574, 356439, G08B 1710

Patent

active

042491690

ABSTRACT:
A reflected light optical smoke detector includes a thermistor in series with a light emitting diode connected in parallel to a photo-resistive cell. Alarm circuitry is connected to the photocell having a voltage output which is a function of the presence or absence of smoke in an examination zone illuminated by the light source and visible to the cell. The circuit is temperature-compensated automatically by the thermistor since the thermistor will increase the current to the LED in the event of an increase of ambient temperature. The increase in the LED light output will compensate for the loss of photocell sensitivity in the event of an increase in temperature.

REFERENCES:
patent: 3315244 (1967-04-01), Voigt et al.
patent: 3383670 (1968-05-01), Roberts
patent: 3555532 (1971-01-01), White et al.
patent: 3922655 (1975-11-01), Lecuyer

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