I bought a 48 volt horn from Amazon to use with the horn output wire on my MP-5. The more I read, though, the less straightforward it gets. First, the horn has only a simple diagram for wiring. It shows the "+" wire going directly (via a fuse) to the battery +, and the "-" wire running, through a button, to ground. The MP outputs (I assume) a +48 volt pulse when the green button is pressed. So how do I wire the horn, and is the fuse needed in this situation? Also, the drawing doesn't make clear which terminal is the + and which the -. They aren't interchangeable, are they...?