Barge is enabled for shared lines only.
The Barge feature enables phone users who share a directory number to join an active call on the shared line. Barge uses the built-in conference bridge on the target phone (the phone that is being barged) which limits the number of users allowed to barge. A barge conference supports up to three parties. When the initiator barges into a call, a conference is created between the barge initiator, the target party, and the other party connected in the call. Parties see the call information on their phones. If a phone that is using the shared line has Privacy enabled, call information does not appear on the other phones that share the line and the call cannot be barged.
Connected parties hear the barge tone (single beep) after the conference is set up. When a party leaves the conference, a barge leave tone is played to the remaining parties.
Cisco Partners or Customer Administrators can enable “Barge” softkey on end users phone. Check the Enable Barge Softkey under “Shared Line Settings” section of the Additional Settings page under Manage Site > Phone > Add Phone and Manage Site > Phones > Modify Phone.