(ab-powering) Some condenser microphones require a power supply in order to operate. If this supply is not from a battery within the microphone body, it is known as a phantom power supply. It is usually 48 Volts DC (can be 9 - 52 volts from most mics), and is supplied either by a separate battery pack, or by the sound desk. The supply is termed "phantom" because it is "invisibly" carried down the same microphone cable as the sound signals.