trying 2 wire extra ir 2 alpine iva 505p

I have a customer who wants to add an extra IR emitter to his Alpine IVA-505P. The manual states that ther are 2 wires 1 in & 1 out that are for IR. Now, long ago I did this on my alpine nav unit bit i no longer own the truck nor do I remember how i did it. I know ir's come with 3 wires so i can't remember if the extra wire needs +/-12v  +/- 5v or ground. I have loads of ir's but don't remember how to wire it up. Hope someone can help

thanks in advance

paul