Research problem		Design a sonar system for a submarine.
	Keywords		navigational system, submarine, pulse generator, navigational system + water, echo ranging, sound navigation ranging
	Borader terms		detectors electronics in navigation ultrasonic equipment signals and signalling + submarine underwater acoustics pigboat submarine u-boat
	Narrower terms		measuring instrument measuring system navigational system acoustic pulse nautical engineering
	Synonyms		Synonyms for "sonar" asdisc echo ranging echo sounder sound navigation ranging Synonyms for "submarine" pigboat u-boat
	Different spellings		"sonar" = sound navigation ranging "asdisc" = anti-submarine detection investigation committee

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