#pinger  a pulse generator used for echo sounding in sonar
  supertype:  #pulse_generator__pulsegenerator  a generator of single or multiple voltage pulses; usually adjustable for pulse rate
  part of:  #sonar__echo_sounder__asdic  a measuring instrument that sends out an acoustic pulse in water and measures distances in terms of the time for the echo of the pulse to return (sonar is SOund NAvigation Ranging; asdic is Anti-Submarine Detection Investigation Committee)
     part of:  #pigboat__submarine__sub__uboat  a submersible warship usually armed with torpedoes

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