ASDIC
An active acoustic system for detecting submarines; the letters ASDIC were said to refer to "Allied Submarine Detection Investigating Committee", the part of the Admiralty responsible for the work, but this may have been a cover story spread around in 1939.
WWI Philip Vassar Hunter collaborated with Admiral W. W. Fisher and William Bragg in a three-man committee to guide the work done by the Admiralty on the development of methods of detecting, locating and destroying submarines. The best known and by far the most fruitful product of this association was ASDIC.
Early work on hydrophones was carried out at the Admiralty Experimental Station, first at Aberdour and later at Parkeston Quay where the active technique, involving sending acoustic signals to be reflected off a submarine, seems to have been developed and the term ASDIC seems to have been first used.
By 1921 there was an ASDIC Section of the Admiralty Signal School[1]
1927-40 the ASDIC Research and Development Unit was at Portland
1940-47 it was succeeded by the Anti-Submarine Experimental Establishment at Fairlie.
c.1944 There was discussion about substituting the term SONAR for ASDIC in the Admiralty's Hydrography unit but no decision was made[2]
1947 The Underwater Detection Establishment was set up at Portland, responsible for research into underwater detection and communications.
1960 The establishment was absorbed into the Admiralty Underwater Weapons Establishment.
The American name SONAR was later more widely used for this technique