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POINT SOURCE DISCRIMINATOR THERMAL ALARM

  • US 3,812,483 A
  • Filed: 05/26/1972
  • Issued: 05/21/1974
  • Est. Priority Date: 05/26/1972
  • Status: Expired due to Term
First Claim
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1. An alarm circuit for an infrared viewer utilizing a cathode ray tube (CRT) display with first and second terminals, respectively, for periodic linear horizontal and vertical sweep signals and a third terminal for an intensity modulation or video signal derived from an infrared detector comprising, at least one horizontal window pulse forming circuit means having an input coupled to said first terminal to generate a pulse of controlled width and having a controlled delay relative to the beginning of each of said periodic horizontal sweep signals, at least one vertical window pulse forming circuit means having an input coupled to said second terminal to generate a pulse of controlled width and having a controlled delay relative to the beginning of each of said periodic vertical sweep signals, an AND gate having at least first and second inputs respectively coupled to the outputs of each of said horizontal and vertical window pulse forming means, a gated amplifier having a first gate signal input coupled to the output of said AND gate and a second amplifier input coupled to said third terminal on the CRT display and a detector means coupled to the output of said gated amplifier to actuate an alarm device when the average signal output from said gated amplifier exceeds a preset threshold.

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