A metal detector is an electronic instrument which detects the presence of metal nearby. Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground. They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects
A Door Frame Metal Detector (DFMD) as the name suggests is a metal detector fitted in a door to detect metal that may be hidden on the body of the person passing through this door. This is also known as a "walk through" metal detector.