Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1980-02-11
1981-09-08
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
Specific condition
250574, 356439, G08B 1710
Patent
active
042887917
ABSTRACT:
A smoke detector which responds to the presence of smoke or other aerosol particles within a smoke chamber. The detector includes a photocell and a pair of light sources, one light source aimed directly at the cell and the other light source shielded from direct illumination of the cell, but aimed at an inspection zone to which the cell is visible. The first light source shines in a generally steady state directly against the cell to bias the cell to a predetermined level. Cyclically, the first light source will be turned off and the second light source will be turned on to illuminate any smoke that may be present in the inspection zone. If smoke is present in excess of that which corresponds to the pre-bias of the cell, the output will rise due to reflection of light from the second light source against the smoke and onto the cell. The output will remain the same if the amount of smoke is equal to the pre-bias and the output will drop if the smoke is less than the pre-bias. Circuitry connected to the cell is adapted to respond to a change in the cell output and to actuate an alarm in the event that cell output is equal to or greater than a predetermined reference. A method for detecting the presence of smoke is also disclosed.
REFERENCES:
patent: 3524707 (1970-08-01), Hansen, Sr. et al.
patent: 3599195 (1971-08-01), Boyko
patent: 4186390 (1980-01-01), Enemark
Caldwell Sr. John W.
Myer Daniel
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