There are many situations where the use of a microphone cable to connect a microphone to other audio equipment is undesirable or impractical. Microphone cables limit a performer's freedom of movement, take away from the visual appeal of a performance and can cause embarrassing incidents if they are stepped on or become caught. Sometimes, as in the theater, the distraction of trailing cables is simply not acceptable. In other situations, such as at major sporting events, news conferences and large public gatherings, using a microphone cable may not be practical.
Wireless microphones use radio transmissions to replace the microphone cable. A wireless microphone system consists of a microphone, a miniature radio transmitter and a radio receiver. The transmitter operates much like a tiny version of an FM radio station. Similarly, the wireless microphone receiver is somewhat like a component FM tuner or home FM radio. Usually, however, the receiver is designed so that it is only able to pick up the signal from one particular matching transmitter. In addition, wireless transmitters operate from batteries so that they will be completely portable.
There are two general types of wireless microphone transmitters, usually called handheld transmitters and body-pack transmitters. Handheld transmitters are somewhat similar in appearance to vocal microphones and include the microphone element, transmitter and battery in one package.
Body-pack transmitters are housed in small rectangular packages that are intended to go into a pocket, be worn on the belt or be concealed on the body. They include the transmitter, battery and a small microphone connector. Body-pack transmitters are generally used with miniature lavalier microphones that are attached to clothing or concealed near the mouth, or with headworn microphones. Musical instruments are often adapted for wireless operation by using body-pack transmitters and special microphones or instrument adapter cables.
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