I inherited a GN Netcom 9120 headset at work. This also meant that I didn’t get a manual so I had no idea on how to use it. With a lot of playing around and some long google searches, I was able to finally figure out how to mute the wireless headset. Hopefully this finding will help others out there.

To mute the 9120 wireless headset, you press the middle (on/off button) twice in under 1 seconds. This will mute the headset. To unmute it you do the same thing; hit the middle button twice in less than 1 second. Its that simple!