Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1979-09-13
1982-06-15
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
Specific condition
179 1SM, 340692, 340628, G08B 1710
Patent
active
043353797
ABSTRACT:
An alarm system responsive to a predetermined concentration of gaseous hydrocarbon in an area. A gaseous hydrocarbon responsive variable resistance element having a heater has resistance characteristics that are relatively stable upon energization of the heater beyond an initial heating period, decrease from the relatively stable value as a function of the concentration of gaseous hydrocarbons in the vicinity of the sensor, and decrease to an initial action resistance value substantially below the stable value during the initial heating period. First and second switching devices connected in series with a power source produce an audible alarm signal with both in their conductive condition. A first trigger circuit triggers the first switching device into its conductive condition in response to the variable resistance element decreasing from the relatively stable value at least to a predetermined resistance value above the initial action resistance value to indicate a predetermined concentration of gaseous hydrocarbons in the vicinity of the resistance element. A second trigger circuit includes a capacitor connected to be charged to at least a predetermined charge level upon energization of the heater and triggers the second switching device into its conductive condition in response to the capacitor achieving the predetermined charge level. A third trigger circuit is connected to the first switching device to intermittently trigger the first switching device into its conductive condition in response to the occurrence of an abnormal condition of the sensor. The alarm circuit can synthesize and annunciate a predetermined spoken message in response to a sensed alarm condition.
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Figaro Gas Sensor TGS #109; 9-20-76, 8 page brochure of Figaro Engineering, Inc.
Figaro TGS Gas Sensor-General Catalogue, 9-20-76; 12 page brochure, Figaro Engineering, Inc.
Figaro Gas Sensor TGS #812; 9-20-76; 5 page brochure of Figaro Engineering, Inc.
Caldwell Sr. John W.
Myer Daniel
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