#pigboat__submarine__sub__uboat  a submersible warship usually armed with torpedoes
  supertype:  submersible_warship__submersiblewarship__submersible  a warship designed to operate under water
  subtype:  attack_submarine  auxiliary_research_submarine  fleet_ballistic_missile_submarine  nautilus
  part:  conning_tower__conningtower  a raised bridge on a submarine; often used for entering and exiting
  part:  escape_hatch  hatchway that provides a means of escape in an emergency
  part:  periscope  an optical instrument that provides a view of an otherwise obstructed field
  part:  snorkel_breather__snorkelbreather__snorkel__schnorchel__breather  air passage provided by a retractable device containing intake and exhaust pipes; permits a submarine to stay submerged for extended periods of time
  part:  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:  pinger  a pulse generator used for echo sounding in sonar
     part:  pulse_generator__pulsegenerator  a generator of single or multiple voltage pulses; usually adjustable for pulse rate

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