Metal detector is an electronic instrument used to locate lost or concealed metal. In the presence of metal, a metal detector gives off a sound, a visual signal, or a vibration. Prospectors, coin and relic hunters, and archaeologists use metal detectors to search for lost or hidden metals or metal objects. Police officers and security personnel use metal detectors to check people for concealed weapons. Manufacturers use detectors to screen packaged goods to ensure that metal objects have not accidentally entered products, especially food products.