Edit: I'm an idiot. On the opposite side of the instructions it specifically says "red wire is the same to provide power at either end. Insulate the unused wire." Derp. 

Rear view camera. Why does the RCA plug need power. Or is that an on-trigger for the head unit? (It’s an active unit so I have to hit the R.Cam button to activate.) I plan on wiring it to a constant 12v so I can turn it on while driving in case I’m towing and want to monitor or whatever. Anyways, why’s that RCA plug need power if the camera is getting it’s own power?