Smoke detection system and method

Details Smoke detection system and method Smoke detection system and method

1979-03-23

1980-12-02

Caldwell, Sr., John W.

Communications: electrical

Condition responsive indicating system

Specific condition

250574, G08B 1710

Patent

active

042374537

ABSTRACT:
A smoke detector is provided in which two light sources are employed in conjunction with a single photo responsive device and control circuit elements adapted for sequential operation of the light sources. One light source is directed at the photo responsive device to pre-bias the device while the other is directed at a smoke chamber to which the device is exposed. If smoke is present in the chamber, the light from the second source will strike the smoke particles and be reflected against the photo responsive device changing the output thereof. The light sources in one embodiment are timed to operate in a series of pulses and measurements are made on the declining output of the photo responsive device, such that the presence of smoke in the chamber will produce a longer decay time than will occur in the absence of smoke. A timer connected to the circuit measures the decay time and is adapted to generate a signal under the appropriate conditions.

REFERENCES:
patent: 3599195 (1971-08-01), Boyko
patent: 4151522 (1979-04-01), Yamauchi

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