I purchased a 700IDT in-dash touchscreen, and I am wondering how to power it at home to test my computer. There are four pins on the power, and I'm not sure which color on a conventional power supply corresponds to which. The manual says "if you are connecting in house, please short yellow and red cable" but I'm not 100% sure which cable is which. There is already something plugged into the back of the head unit with a red wire going from one pin to the other (to form a loop) and a black wire sticking out. Should the black wire be connected to a black wire (ground) from the power supply and should the red "loop" be connected to both the red and yellow from the power supply? Any suggestions would be appreciated, thanks.