Originally Posted by Hark
Do you want to mute the sound, or also stop the song where it is, to continue later when you are off the phone. Also, I assume that your carputer plays through your car stereo.
If the first, you can do what I did. Connect the mute wire (it is a ground signal when it want to mute) to a relay, and put the relay in the accessory/ignition wire that leads to your stereo. In that way, when the CK3100 wants to mute, it flips the relay, breaking the connection to the stereo, turning it off. Then, when the call is done, the relay "un flips" and the stereo turns back on.
The advantage to doing it this way is if the car stereo is playing a tape of CD, the song stops where it is, and will continue when the call is over. Of course for radio, and/or the carputer, it will not stop the song in it's tracks, but at least it will mute.