Title: Light decrease type smoke sensor

Abstract: A smoke detector includes a light-emitting circuit, a light-receiving circuit, a smoke detecting space between the light-emitting and receiving circuits, and an amplifier circuit connected to the light-receiving circuit amplifying the output of the light-receiving circuit at an output terminal. An output comparison circuit is provided having an input terminal connected to the output terminal of the amplifier circuit and a voltage memory circuit is connected to another input terminal of the output comparison circuit. A detector circuit has one input terminal connected to the memory circuit and another input terminal connected to the output terminal of the comparison circuit, and a fire alarm circuit is connected to the detector circuit for operating an alarm when smoke from a fire fills such space between the light-emitting and receiving circuits, whereby contamination due to time and environmental factors has a minimal adverse effect on the detection of smoke in such space.

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Inventors: Yamauchi, Yukio (Kawasaki, JP)
Homma, Hiroshi (Tokyo, JP)

Application Number: 907466
Filing Date: 1978-05-19
Publication_date: 1980-05-13
Assignee: Hochiki Corporation (Tokyo, JP)
Primary Class(es): 340/630 250/573
Other Classes:
US Patent Ref:

3846772	Nov, 1974	Peberdy	340/630.
3919702	Nov, 1975	Hayes et al.	340/630.
4011458	Mar, 1977	Malinowski	340/630.

Other Refs:
Primary Examiner: Caldwell, Sr., John W.
Assistant Examiner: Myer, Daniel
Attorney: Jordan; Frank J.