Handsfree kit

I just got a Motorola HF850 handsfree kit for my 02 TL-S w/nav. It has a wire to tap into the radios mute input. The nav mutes the radio but I have not been able to find any information on which wire is the correct one to tap into. Has anyone installed a handsfree kit in their TL and if so does it mute? Any info will be greatly appreciated.

Thanks, Mike