This clever little box allows you to send a baseband video signal and a pair of audio signals over a standard category 5 cable, without worrying about noise, hum, and other forms of interference. It takes two of these devices, one on each end, to send a signal. And it takes one pair in the Cat 5 cable for each of the video and audio signals. We don't really recommend creating a whole-house audio/video distribution system out of these devices...but when you get stuck, they can bail you out and get that signal from point A to point B. This item is sold in single and you will need two of them.