Function test means of photoelectric type smoke detector

Details Function test means of photoelectric type smoke detector Function test means of photoelectric type smoke detector

1984-03-26

1987-03-03

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250205, 340630, G01N 1506

Patent

active

046477853

ABSTRACT:
A photoelectric smoke detector is provided with first and second radiation emitters and first and second radiation receivers. The first emitter emits pulsed radiation at a predetermined frequency. The second emitter emits pulsed radiation at twice this frequency. The first receiver receives the radiation of the second emitter directly and that of the first emitter by scattering only. When the first receiver receives alternate detection pulses reinforced by scattered radiation, an alarm is generated. The second receiver receives radiation directly from the first emitter and modulates the radiation output level of the second emitter proportionately. When the first receiver receives testing pulses between the alternating detection pulses, their level is discriminated to determine the functional state of the detecting elements and a corresponding function signal is generated.

REFERENCES:
patent: 3736431 (1973-05-01), Childs
patent: 4206456 (1980-06-01), Malinowsky et al.
patent: 4555634 (1985-11-01), Muggli et al.

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