Sonar
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Sonar is a technique that uses sound propagation to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.
French F70 type frigates (here, La Motte-Picquet) are fitted with VDS (variable depth sonar) type DUBV43 or DUBV43C towed sonars.
Sonar image of the Soviet Navy minesweeper T-297, formerly the Latvian Virsaitis, which was shipwrecked on 3 December 1941 in the Gulf of Finland
Bubble clouds shown under the sea. From ref.
Variable depth sonar and its winch
Reginald Fessenden
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Reginald Aubrey Fessenden was a Canadian-born inventor who received hundreds of patents in various fields, most notably ones related to radio and sonar.
Whitney Institute in Bermuda, founded in 1881, of which Fessenden was headmaster
Located near Fessenden's birthplace, this plaque was installed by the Historic Sites and Monuments Board of Canada
It reviews his telecommunications and submarine detection work