OK, well its takes an input from your speedo and tacho(pretty easy to locate if you've got a haynes or gregorys), as well as 12V from accessorys power. Its got a connection for reverse(12V of the reverse lamps) so when you go into reverse it displays an (r). When you either in neutral or at a complete standstill the unit displays (-). You then go out on a long stretch of road and go into each gear programing the unit, so it basically learns once and thats it. I works very well.
AU XR lookalike wagon