Fred Malibu

Yes, they plug into the back, but when you buy the horn, it doesn't just come with a wire and the little silver plug that goes in the back (3.5mm jack..). Normally, because the applications for this horn are so great in number, they are left with a small cord attachment where you have to sodder your own cord length (and 3.5mm jack). This was the case when I bought mine a couple months back. If you do not know how to sodder, I have a horn with the cord already done which I can sell to you. Otherwise, you can go to Radio Shack and buy the stuff and sodder it yourself (or buy a horn on Ebay that is presoddered, only down side is that you cannot choose your own length cord).. Also, you have to go through a hole to connect your horn into your engine bay (assuming it is being mounted under the hood..)
Any more ?s and I'll try my best to help.
Thanks, FM