The XLR connector is a three pin electrical connector that is found professional audio, video, and stage lighting equipment. It is typically the type of connector found on microphones and is best used when plugged into a balanced input on a mixer. XLR connectors are designed to be mono and be electrically balanced. One pin is used for the ground cable then the other two pins are used for the audio. Two pins are used for the audio with the sound being 180 degrees out of phase on one of the wires. When plugged into a balanced input on a mixer, a differentiator detects any noise picked up on the cable and the noise is cancelled out.