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GLASS BREAKAGE DETECTOR

  • US 3,863,250 A
  • Filed: 01/30/1973
  • Issued: 01/28/1975
  • Est. Priority Date: 01/30/1973
  • Status: Expired due to Term
First Claim
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1. In an alarm for sensing vibrations in a sheet of glass capable of breaking the glass, a vibration sensor comprising a piezoelectric element responsive to vibrations to generate an output signal, means for mounting said sensor directly on and adhered to the sheet of glass, mechanical filtration means interposed between said piezoelectric elemEnt and the sheet of glass for blocking from said piezoelectric element vibrations of a frequency and magnitude incapable of breaking the glass, and electrical circuit means coupled to said piezoelectric element for generating an alarm signal in response to an output signal from said piezoelectric element, said electrical circuit means being responsive to said output signal only when the latter reaches a voltage corresponding to mechanical vibration of the sheet of glass of a frequency and magnitude capable of breaking the glass.

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