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Smoke, fire and gas alarm with remote sensing, back-up emergency power, and system self monitoring

  • US 4,088,986 A
  • Filed: 10/01/1976
  • Issued: 05/09/1978
  • Est. Priority Date: 10/01/1976
  • Status: Expired due to Term
First Claim
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1. A smoke, fire and gas alarm characterized by a plurality of remote sensors and a central control and alarm unit, comprising:

  • A. a plurality of remote gas sensing means which respond to the presence of carbon monoxide and the like by a lowered electrical resistance; and

    B. a centralized power supply operable for generating a D.C. supply voltage to each of said remote sensors, and for generating further distinct voltage levels VL1 and VL2, said power supply being characterized by a normal supply source and an alternate supply source, and including automatic means to switch therebetween; and

    C. centralized threshold circuits for each of said remote sensors, each threshold circuit being adapted to compare said voltage level VL2 with a voltage from its associated sensor to produce a sensor output voltage; and

    D. a centralized processing unit for receiving a sensor output voltage from each of said threshold circuits, said processing unit comprising logic element means for comparing each of said plurality of sensor output voltages with said voltage levels VL1 and VL2, said logic means further being adapted for generating an enabling processing unit output signal in response to either increase or a decrease of any of said sensor output voltages; and

    E. a centralized alarm power drive for receiving said processing unit output signal, said alarm drive comprising a oscillator for generating a variable alarm signal; and

    F. a centralized alarm, responsive to said alarm signal, and further comprising an interruptor device having means to prevent ignition of an explosive gas in the vicinity of said alarm.

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