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Underwater target detection apparatus

  • US 3,976,968 A
  • Filed: 11/19/1954
  • Issued: 08/24/1976
  • Est. Priority Date: 11/19/1954
  • Status: Expired due to Term
First Claim
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1. In an active acoustic underwater target detection system, in combination:

  • means for periodically transmitting pulses of acoustic energy, means for receiving reflected acoustic energy including reverberation and echo-pulses, means for automatically adjusting the carrier frequency of the transmitted pulses so that the frequency of the resultant reverberation as received has a predetermined fixed value, means for producing a first electrical signal when a reflected echo-pulse is received whose frequency differs from said predetermined fixed value, means for producing a second electrical signal when a reflected echo-pulse is received whose amplitude is above a predetermined magnitude, a coincidence circuit for producing a signal when said first and second signals occur simultaneously, and relay means controlled by the signal produced by said coincidence circuit.

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