Copied from the analog phone manual.
Conference- LINK *3
Allows you to establish a three-way conference between yourself, one
external call and one internal call, or two internal calls. Line pool access
allows you to establish a conference between yourself and two external calls.
To establish a conference:
1.Make or answer the first call.
2. Press LINK,"2". The first call is automatically put on hold.
3.Make or answer the second call.
4. Press LINK *3 to complete the conference.
Note: If the second call is busy, replace the handset and press LINK, "2" to return to
the first call.
To put a conference on hold:
Press LINK '2".The other two callers can still talk to each other.
To return to the conference call: Press LINK "2" again.
To split a conference:
1. Press LINK, #, "3". This allows you to put one caller on hold and to consult
with the other caller.
2. Press LINK, "2" to alternate between callers.
To re-establish the conference: Press LINK,* "3".
To disconnect one party:
1. Press LINK,# "3" . This allows you to put one caller on hold.
2. Press LINK,"2" to alternate between callers.
To end a call: Finish your conversion then replace the handset.
To retrieve the held call: Press LINK,"2".