Originally Posted by UCrewX5

The common way to do this is using a relay. When the vehicle is put into reverse you can sense the voltage to one of the back-up lights and use that to trigger a relay. The relay will take one of the leads in the video module wiring harness to ground, triggering the system to display the video signal from the backup cam. See page 21 on this document for more details - http://www.tvonnav.com/manuals/TVonN...anual%20v4.pdf