How Does a Cordless Microphone Work?

What Are Cordless Microphones and What Are They Used For?

Cordless microphones, also called wireless microphones, are composed of two basic components: the microphone/transmitter and the receiver. They are used for many types of video production, including talk shows, documentaries and news programs. Cordless microphones are also used in many concert performances so the performers can move about the stage without dragging cords behind them. There are two basic types of wireless microphones.

The Self-Contained Cordless Microphone

A self-contained cordless microphone consists of a standard handheld microphone with a transmitter built into it, like the type used in concert performances or on many newscasts. The microphone picks up sound vibration and converts it to an electrical signal just like any other microphone; this signal is then relayed to a small battery-powered transmitter that converts it into a signal that is transmitted over the airwaves. The transmitter is built into the handle of the microphone.

Some wireless microphones have a small antenna extending from the bottom of the microphone handle. This is basically the same technology as that used by your cell phone, except that the electronics are of a much higher quality.

The Lapel Wireless Microphone

Another type of cordless microphone that is widely used on TV talk shows and to produce documentaries is the lapel wireless microphone. You may have seen the little microphone clipped to a television host's lapel and a small box clipped in back at the host's waist. Lapel wireless microphones allow the host to move around and have both hands free. They work the same way as the concert-type cordless microphone, except that the microphone and transmitter are separate and have a tiny wire connecting them.

Lapel-type microphones are more convenient for television production. When filming a panel discussion or talk show, each person is fitted with a wireless microphone. Each microphone is assigned a separate channel, allowing the director to adjust the volume of each microphone independently and switch the microphone off when a person leaves the stage. A special lapel-type cordless microphone is also used in undercover police work and referred to as "wearing a wire."

The Receiver

For the sound signal transmitted by the cordless microphone to be usable, it must be captured by another device--this is what the receiver does. The receiver is located near the auditorium sound amplifiers or the video recording equipment. Once this sound is received by the receiver, it must be put on videotape or, in the case of a concert, input into the auditorium sound system. So the receiver captures the transmission from the wireless microphone, converts that transmission to a signal that can be used by the audio or video equipment and provides an output that can be plugged into the amplifier or video camera.