Smoke detector

Details Smoke detector Smoke detector

1979-12-19

1982-03-23

Caldwell, Sr., John W.

Communications: electrical

Condition responsive indicating system

Specific condition

250574, G08B 1710

Patent

active

043215955

ABSTRACT:
A smoke detector containing a radiation source operating in a pulsed mode and a scattered radiation receiver connected in a coincidence circuit. This circuit contains a counter which counts both the radiation pulses and the incoming scattered radiation pulses. With undisturbed operation this counter, following each radiation pulse, has an even numbered counter state. The appearance of an uneven numbered counter state is indicative of the presence of spurious pulses and leads to resetting of the counter to null, so that there is prevented attainment of a counter state adequate for tripping an alarm signal. On the other hand, with the presence of a predetermined even numbered counter state there is triggered an alarm. Such smoke detector is almost immune to spurious pulses and does not tend to trigger faulty alarm signals.

REFERENCES:
patent: 3316410 (1967-04-01), Meili et al.
patent: 3946241 (1976-03-01), Malinowski

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