Smoke detector with a radiation source operated in a pulse-like

Details Smoke detector with a radiation source operated in a pulse-like Smoke detector with a radiation source operated in a pulse-like

1982-06-08

1985-03-19

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

340630, G01H 1506

Patent

active

045061610

ABSTRACT:
A smoke detector contains a pulse-operated radiation source and a radiation receiver arranged externally of the region directly irradiated by the radiation source. The radiation receiver, in the presence of smoke in the radiation region, is impinged by scattered radiation and delivers output pulses. There is provided an evaluation circuit which generates a blocking pulse, and which inputs a resetting signal to a counter device in consequence of the difference of the blocking pulse and output pulse of the radiation receiver. The counter or counting device, in the absence of a resetting signal, is switched further and upon reaching a predetermined counter state triggers an alarm signal. High-frequency electrical disturbances which arise, as long as the radiation source delivers radiation pulses, at most can generate an additional resetting signal for the counter, so that the integrity of the smoke detector against triggering of false alarms is enhanced. If there is connected in parallel to the radiation receiver a NTC-resistor, then there is obtained a smoke detector which responds to a further combustion criterion (temperature).

REFERENCES:
patent: 3846773 (1974-11-01), Lintelmann
patent: 3922656 (1975-11-01), Horvath et al.
patent: 4260984 (1981-04-01), Honma
patent: 4297688 (1981-10-01), Kakigi
patent: 4321595 (1982-03-01), Tresch
"Electronics"--Optoelectronic Alarm Circuit is Time-sensitive, by Forrest M. Mims III, vol. 52, No. 14, p. 133, Jul. 1979.

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