Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1977-06-15
1979-04-24
Swann, III, Glen R.
Communications: electrical
Condition responsive indicating system
Specific condition
3403091, 340628, G08B 1700
Patent
active
041515226
ABSTRACT:
A fire detector senses the change in a physical parameter indicative of a fire such as smoke, heat or the like and produces detection pulses in synchronism with an oscillator circuit when the change in the physical parameter exceeds a predetermined amount. A counting means counts the detection pulses and produces an output which triggers an alarm circuit when a predetermined number of consecutive detection pulses are counted. The count of the counting means is reset by a reset means whenever the detection pulses are nonconsecutive, that is, whenever an oscillator pulse is received without receipt of a corresponding detection pulse. By this means intermittent changes in the physical parameter which indicate some false alarm signal rather than a real fire do not produce the required number of consecutive detection pulses and do not set off the alarm circuit. On the other hand when a real fire occurs the circuit always counts detection pulses from the beginning of the detection of a fire because the counting means is reset each time a series of consecutive detection pulses less than the predetermined number ends.
REFERENCES:
patent: 3621262 (1971-11-01), Lecuyer
patent: 4065758 (1977-12-01), Barbier et al.
Hochiki Corporation
Swann III Glen R.
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