It is possible to operate the headset "stand alone" or to pair the headset with a handset registered at the base station. The headset will get the ame extension number as the handset, and you can assign its former extension number to another terminal.
On the extension page, click on the IPEI of the handset. The handset page opens.
Click Save. The headset is now registered with the same extension number as the handset and can also be used to call numbers dialed on the handset's keypad.