307 reversing camera auto opening aid

Let's just go, I bought a Roadstar 9115N model tape, I installed the rear view camera at the weekend and got the electricity in the reversing lamp, so far there is no problem.

however, when I put it automatically in reverse, it does not appear on the screen, I can see the image if I enter the relevant screen from the menu, I have researched a little about the subject, I have read something like "trigger" but I can not say that I understand it very much.

Behind the tape, the camera cable was a coaxial cable, and there was a "Cam" input, I inserted it there, but next to the jack from the camera I installed, there is a red cable and it is now idle. Because I don't know where to hang.

as a result, I want the reversing camera to come automatically when I shift into reverse. I don't know if there is anybody.

There was a cable output called "Reverse" on the back of the tape, I connected the cable that was idle on the camera cable to Reverse. Now when I put it in reverse, no matter what is on at that moment, the view of the reversing camera is displayed.