Sonar

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Sonar was a detection system based on sound waves. It was considered a form of underwater radar which sent out regular sound signals, with the intention that they would reflect off any metal object. Sending and receiving reflected signals could each be detected by a 'ping' noise, heard through earphones, and the time between two 'pings' could be used to determine the distance between the sonar system and the metal object. (PROSE: Doctor Who and the Sea-Devils)

History

In 1941, the United States was in the process of developing sonar. (AUDIO: Dark Convoy)

A sea-fort in the English Channel was converted into a sonar testing centre. (TV: The Sea Devils)

A blind predator used "a kind of sonar" to find its victims. (AUDIO: See No Evil)

A signal transmitted by the Game Station masked the Dalek Fleet from sonar, radar and scanners. After he was taken to the Game Station in 200100, the Ninth Doctor cancelled this signal, revealing who was manipulating mankind. (TV: Bad Wolf)

The First Doctor used a sonar device called an echo-sounder to determine the depths of the marsh he, John and Gillian were walking through, enabling them to get to the Pied Piper's castle. He later used it to find the Piper after he turned himself invisible. (COMIC: Challenge of the Piper)

General Ironicus' Iron Legion could detect the heartbeats of humans and similar humanoid life forms with their sonar. (COMIC: Doctor Who and the Iron Legion)

By 2065, Astran flying saucers were equipped with long range sonar scopes. (COMIC: President Offers Peace...)