Metal detector is an electro magnetic device, with lines passing through a metallic object. They use either static or pulsed magnetic field. Generating eddy current on a metal detector distorts the normal electro magnetic field. These eddy currents are measured and when they exceed a certain level audible or visual alarm goes off. Thus the operator intervenes to ascertain the presence or absence of a dangerous weapon or object. Metal detectors may be portal or wand. These instruments damage electronic equipments. No metal detectors can ever be expected to function at 100 percent efficiency. Metal detectors are used frequently to increase security at schools, transportation terminals, courts and prisons.