yah thats how is was originaly setup, but i have a, well lets say a bit above average stereo istalled, and when it all kicks in my voltage would drop for some reason, so the only way was to simulate a voltage or tach, so thats what we had to do. I finnaly wired my train horns in to the alarm wire, so if you loiter around the truck for to long you get a nice 130db train horn blast.