Phantom power is a method of remotely powering microphones that require electricity to operate. This applies mainly to condenser microphones. These microphones contain active electronic circuitry, such as a small internal preamplifier, and their condenser capsule needs electrical voltage to function properly. In contrast, dynamic microphones do not need an external power supply because they generate the necessary weak electrical signal themselves by moving a coil in a magnetic field. The power supply is referred to as "phantom" because it is invisible to the microphone signal and is sent over the same standard XLR microphone cable through which the audio signal travels. Specifically, it is a DC voltage, most commonly +48 volts, that is applied to both signal wires of the cable. Microphones that do not require this power supply, such as the dynamic microphones just mentioned, simply ignore it and it does not affect their function. The source of this power supply is usually the device into which the microphone is plugged, such as a mixing console, external sound card or microphone preamplifier, where a switch labeled "Phantom" or "+48V" is usually located to activate it.
