metal detector

Electronic device for detecting metal, usually below ground, developed from the wartime mine detector. In the head of the metal detector is a coil, which is part of an electronic circuit. The presence of metal causes the frequency of the signal in the circuit to change, setting up an audible note in the headphones worn by the user.

They are used to survey areas for buried metallic objects, occasionally by archaeologists. However, their indiscriminate use by treasure hunters has led to their being banned on recognized archaeological sites in some countries.