A wireless microphone, or cordless microphone, is a microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated. Also known as a radio microphone, it has a small, battery-powered radio transmitter in the microphone body, which transmits the audio signal from the microphone by radio waves to a nearby receiver unit, which recovers the audio. The other audio equipment is connected to the receiver unit by cable. In one type the transmitter is contained within the handheld microphone body. In another type, called a "lavalier microphone" or "lav", a small microphone clipped to the user's lapel is connected by wire to a transmitter unit concealed under his clothes. In a third type the transmitter is a headset, with a microphone on a boom extending in front of the user's mouth. Wireless microphones are widely used in the entertainment industry, television broadcasting, and public speaking to allow public speakers, interviewers, performers, and entertainers to move about freely while using a microphone to amplify their voices.