I’m not sure exactly how my rear cam is wired in cuz I had a shop do it, but’s wired to my reverse line so it automatically engages when I put my truck in reverse. But it’s also wired into another constant power source as my head unit has the option already to pull it up when reverse isn’t engaged. So when, for instance towing a jet ski trailer I can pull up my camera with my shortcut button, when I can’t see the jet ski tagging along in the mirror and make sure it’s where I want it. It’s quite the angst