My X came with Sirius radio, which I don't want. So I removed the tuner and antenna (for sale now, $100, any takers?)

Anyhow, the Sirius box has an input/output that goes unused, and I don't know what it's for. There's the plug for the antenna, there's the harness that plugs it into the factory radio, and then there's a THIRD plug, that's unused, which is similar in shape to the radio-connect plug but slightly larger.

I've never heard of this tuner having another plug, and I can't figure what it's for, unless it's for adding another cd-changer or other auxiliary device while still keeping your satellite radio (since there is only one input on the back of the Rockford radio itself).

So here are the pictures:






Anyone have any thought as to what this extra plug is for?

Maybe it's a daisy chain setup so you can connect a trunk mount CD changer or something and it would connect to the stereo via the Sirius tuner? That's how it works with my Pioneer setup.