Panasonic 2001 - Manual (Page 48)

Talking with more than one person
48
To answer a Group Call:
Note: When you answer a Group Call, three 10-second tones notify
you that there is a group call on your extension.
To end a Group Call:
Lift the
handset.
(Goodbye)
Press the
Goodbye key.
Note: When the person who made the
group call disconnects, the call
terminates for all members of the group.
However, the members of the Group Call
can disconnect from the call and not
affect other members on the call.