AASTRA 4422 IP Office (SIP) for MX-ONE User Guide - Manual (Page 46)

During Calls
Dialog 4422 IP Office 46
3
Press
or Ô
Conference press to establish a conference.
Repeat the procedure to add more conference members. d
Replace the handset to leave the conference.
Note: When the conference leader leaves the conference,
the conference will continue with the other included parties.
The conversation is changed back to a normal two party
connection when there are only two parties left.