Indicator Loops were long lengths of cable laid on the seabed to detect enemy submarines. They were developed by the Royal Navy in the early 1900s and used in their ports both home and in the Dominions (Australia, Canada, New Zealand, Ceylon, Penang). They were further developed by the United States Navy from 1940 onwards. This page documents the Royal Navy's indicator loop history.
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Dr Richard Walding
Research Fellow - School of Science