Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1980-08-11
1982-02-23
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
Specific condition
250565, 250573, 356438, G08B 1710
Patent
active
043171133
ABSTRACT:
In a photoelectric smoke sensor which produces a fire alarm signal when an amount of attenuation of received light exceeds a predetermined level due to smoke flowing into a space between light emitting and light receiving devices, the level of a receiving light signal from the light receiving device is converted by a converting level control signal. An initial value of the receiving light signal is converted into a digital quantity which is stored in a memory circuit. The digital content of the memory circuit is then converted into an analog quantity. The analog quantity is then compared with the level-converted receiving signal to produce a fire alarm signal. The analog quantity and the level-converted receiving signal are compared with each other at a predetermined period to correct the converting level control signal when there is a difference between the analog quantity and the level-converted receiving signal as a result of the comparison. With such a scheme, a change of an amount of received light due to dust or dirt of an optical system of the smoke sensor is automatically corrected. When the level correction reaches a limit, an alarm is issued for inspection and maintenance of the sensor.
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Caldwell Sr. John W.
Hochiki Corporation
Myer Daniel
LandOfFree
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