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Intruder detecting system

  • US 3,109,165 A
  • Filed: 09/05/1958
  • Issued: 10/29/1963
  • Est. Priority Date: 09/05/1958
  • Status: Expired due to Term
First Claim
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1. A SYSTEM FOR DETECTING FOOTSTEPS OF AN INTRUDER UPON AN AREA OF GROUND WITHIN A BOUNDARY, SUCH FOOTSTEPS CAUSING SONIC ENERGY TO BE CONDUCTED THROUGH THE GROUND WHICH SYSTEM COMPRISES TRANSDUCER MEANS IN THE GROUND LOCATED A PREDETERMINED DISTANCE FROM THE BOUNDARY, SAID TRANDUCER MEANS BEING OPERABLE TO RECEIVE SONIC ENERGY CONDUCTED THROUGH THE GROUND AND OPERABLE TO PRODUCE ELECTRICAL ENERGY AT ITS OUTPUT CORRESPONDING IN FREQUENCY TO THE FREQUENCY OF THE SONIC ENERGY RECEIVED, THE AMPLITUDE OF THE SONIC ENERGY BEING ATTENUATED TO A DEFINITE RANGE OF LOW AMPLITUDE VALUES AT HIGH FREQUENCIES WITHIN A GIVEN BAND AFTER PASSING THROUGH THE GROUND FOR A PREDETERMINED DISTANCE, ELECTRO-RESPONSIVE RECEIVING MEANS HAVING ITS INPUT CONNECTED TO THE OUTPUT OF SAID TRANSDUCER MEANS INCLUDING A FREQUENCY AMPLIFIER TUNED TO SELECTIVELY DETECT ENERGY AT A PREDETERMINED FREQUENCY TO PRODUCE AN OUTPUT AND FILTER OUT ENERGY AT FREQUENCIES OTHER THAN THE PREDETERMINED FREQUENCY, AND ALARM MEANS CONTROLLED BY THE OUTPUT OF SAID RECEIVING MEANS.

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