Communications: electrical – Systems – Call station
Patent
1975-01-29
1977-01-18
Caldwell, John W.
Communications: electrical
Systems
Call station
340248B, 340249, G08B 1710
Patent
active
040042880
ABSTRACT:
A battery operated fire detection unit that is capable of independent monitoring through sensing of smoke with the unit maintaining monitoring capabilities over long periods of time. A smoke detector senses the presence of smoke indicative of a fire and, when above a predetermined threshold, produces an electrical output signal that is coupled through latch circuitry and a logic gate to an audible alarm, such as a horn. An oscillator is also provided, the output of which is coupled through a differentiator to a logic gate, which gate also receives the output from the latch circuitry connected with the smoke detector. In the absence of a sensed fire condition, a light is periodically energized at a rate dependent upon the oscillator frequency to indicate that the system is operable, and the light is constantly energized to indicate the sensed presence of fire. An automatic battery, or low voltage, monitoring circuit is also provided to actuate the audible alarm when the sensed voltage drops below a predetermined minimum to indicate the need for battery replacement.
REFERENCES:
patent: 3717862 (1973-02-01), Sasaki
patent: 3842409 (1974-08-01), Mayer
patent: 3866195 (1975-02-01), Ried, Jr.
Caldwell John W.
Myer Daniel
Unitec, Inc.
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