Schematic for how I wired my outside lights. I have two in the back above the dropdown door and two on each side up high front and back. I wanted the lights to function in three different modes. 1) Turn on and off individually when the trailer is free standing and powered by the internal 12v supply. 2) Turn on and off individually when the trailer is hooked to tow vehicle and use power from tow vehicle. 3) Turn on and off automatically when the the tow vehicle is placed in reverse, using vehicle power.