Phantom power, in the context of professional audio equipment, is a method for transmitting DC electric power through microphone cables to operate microphones that contain active electronic circuitry. It is best known as a convenient power source for condenser microphones, though many active direct boxes also use it. The technique is also used in other applications where power supply and signal communication take place over the same wires.
Phantom power supplies are often built into mixing desks, microphone preamplifiers and similar equipment. In addition to powering the circuitry of a microphone, traditional condenser microphones also use phantom power for polarizing the microphone's transducer element. Three variants of phantom power, called P12, P24 and P48, are defined in the international standard IEC 61938.