I have a Kenwood DDX 393 head unit which has a reverse wire on the back that I assume is to be tied into a reverse wire on my truck. My question is, since my camera is one that ties into the reverse light on the back of my truck then the video cable to the head unit, do I need to also hook up that wire on the back of the head unit as well? It seems to me that would be redundant but I guess it could also be the only way the head unit knows the car is in reverse. Any help is appreciated, Thanks!