An audio-visual appliance is a device that displays, captures, transmits, or receives audio or video. They may be fixed in place or may be able to be moved from one space to another.
A microphone is an audio-visual appliance that is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. Microphone types include electromagnetic induction (dynamic microphones), capacitance change (condenser microphones) or piezoelectric generation to produce the signal from mechanical vibration.