Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1977-07-13
1978-11-14
Nelms, David C.
Communications: electrical
Condition responsive indicating system
Specific condition
250574, G01N 2126
Patent
active
041257790
ABSTRACT:
A smoke detector of the type utilizing a pulsing light source and photo-responsive means producing an output signal in response to the receipt of a pulse of light from said source reflected from smoke particles and means for amplifying said output signal to produce an alarm signal, which has exceptionally low current drain so as to be adapted for being powered by a battery, and exceptional immunity to false alarms even when operated at a high sensitivity. On each pulse, the amplifier is energized and allowed to achieve a stabilized condition, prior to energizing the light source, and after the light source is energized, the amplified output signal is not allowed to create an alarm signal until the circuit has again stabilized from transients caused by the energizing of the light, thereby preventing false alarms from circuit transients resulting from internal and external causes.
The circuit operation is controlled by a master clock which provides a slow pulse rate during stand-by operation and an increased pulse rate when an alarm signal is produced in response to the presence of smoke. The clock also causes the alarm to be energized by pulses, which provides a more attention-getting alarm signal than does a continuous alarm, and conserves the strength of the battery.
REFERENCES:
patent: 3874795 (1975-04-01), Packham et al.
patent: 3892485 (1975-07-01), Merritt et al.
patent: 4065759 (1977-12-01), Handing
Chloride Incorporated
Nelms David C.
Ross Robert E.
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