Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1995-06-07
1996-09-17
Swann, Glen
Communications: electrical
Condition responsive indicating system
Specific condition
340522, 340529, 340577, 340628, G08B 1700, G08B 1706, G08B 1710
Patent
active
055572626
ABSTRACT:
A fire alarm system utilizes outputs from different types of fire sensors, such as photoelectric smoke sensors or ionization type smoke sensors and combines those outputs by subtraction so as to establish a delay interval during which one or both of the sensor output values must exceed a predetermined threshold value to cause the system to go into an alarm condition. Prior to subtracting the outputs from one another, each of the outputs can be raised to a predetermined exponential value so as to emphasize the effects of larger sensor output values. Where the two types of fire sensors each are generating outputs indicative of a fire condition, the calculated delays will be relatively short. In instances where only one of the two sensors is generating an output indicative of a fire condition, the calculated delay will be longer, so as to inhibit false alarms.
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Pittway Corporation
Swann Glen
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