Aux outputs from my alarm

I was wondering could I use my Aux output from my alarm to turn on my stereo system and turn it off it only puts out a has a .75second output of negative current and then when you let go it closes, I have a Avital Phoenix2, I know ayou have to use relays could someone make me a diagram. 

Thanks in advance

I called the local sound shops and that part is from 35 to 40 dollars.  I just bought one on e-bay for 4.99.  I hope this works. I eally appereciate it.

Thanks