The 9120 operates on the same principles as the CS50 or other wireless headsets, the cords are simply in a little different location.
Begin by removing the charging stand (the silver and black base) off of the black stand.
At the very bottom of the charging stand, you’ll see 3 jacks from left to right:
Lef t- an RJ11 “AUX” jack
Middle - an RJ9 jack with a telephone icon below it and an RJ9 cord already connected
and a second RJ9 jack that has a handset icon below it.
The curly cord from the handset plugs into the handset jack on the far right.
The RJ9 cord that’s already connected to the jack with the phone icon below plugs into the phone, where the curly cord was.
The DCA power supply plugs in on the far left in a very small round hole.
Replace the headset on the stand and you should see the power indicator light on the front of the stand (the narrow black portion that says GN Netcom)
Let it charge for an hour and a half and try it out!