This microphone plugs directly into the MIC jack of the DVR unit, and allows you to capture audio externally, instead of relying on the built-in microphone of the unit. It's a great addition for when the DVR is mounted far away from the sound source, or just to upgrade the standard mono recording to a 2-channel stereo sound. The standard cable length is 110cm (40 in.) and can be extended easily, using the LLE-XX extensions.