Wireless microphones have been around since the 1940s in virtually the same format as they are today. They consist of a mic fitted with a radio transmitter which sends radio waves to a nearby receiver. This device then decodes and distributes the audio information to the sound system.
There are three general wireless microphone types. 'Handheld' are dedicated units that look similar to a standard mic, though usually with a larger body to house the transmitter and battery. 'Plug-in' models can be fitted to any standard mic, while 'bodypack' units have a clip-on box containing the transmitter and battery attached to a wired headset, lapel microphone, or even an instrument such as a guitar.