RF field intensity meters are used measure the strength of an electromagnetic field. These instruments or receivers are used to detect buried or hidden piping, equipment, and ferromagnetic ores. They are also used to detect cellular phones, remote cameras, audio surveillance or bugging devices, and other products that use radio frequency (RF) transmissions. For example, RF field intensity meters that detect cellular phone transmissions are often used in hospitals, medical centers, military installations, and sensitive manufacturing facilities.