Lots More Information Prev Next Related HowStuffWorks Articles How Radio WorksHow Oscillators WorkHow Iron and Steel WorkHow Airport Security WorksHow Telephones WorkHow Batteries WorkHow Speakers Work More Great Links U.S. Patent # 4,868,504: Apparatus and method for locating metal objects and minerals in the ground with return of energy from transmitter coil to power supplyU.S. Patent # 5,506,506: Metal detector for detecting and discriminating between ferrous and non-ferrous targets in ground
