In the world of wireless performance a body pack is the device a performer wears somewhere on his or her body that houses the electronics that handle sending a signal to a remote receiver or, as in the case of personal monitoring systems, receives a signal from a remote location. Typically body packs hold a battery and some combination of electronics that do the transmitting or receiving, and amplifying. Some wireless systems do not require a body pack as all of these electronics can be housed right inside of a microphone or a small plug that can be connected directly to a guitar or other musical instrument.