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Fire detecting system

  • US 4,975,684 A
  • Filed: 06/09/1989
  • Issued: 12/04/1990
  • Est. Priority Date: 06/10/1988
  • Status: Expired due to Fees
First Claim
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1. A fire detector for protecting premises periodically occupied by workers and operating machinery, said fire detector comprising:

  • at least one first sensor for emitting a first output signal in response to a fire phenomenon,at least one second sensor for detecting a source of false alarm conditions, said false alarm conditions being detected from the presence and activities of said workers and operating machinery andan evaluating circuit,said evaluating circuit comprisingmeans for providing an alarm signal in response to a value of said first output signal exceeding a threshold value andmeans for changing said threshold value relative to said first output signal value in response to a second output signal from said second sensor.

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