Comdial 8312S System Reference Manual page 56

Conferencing Calls
To retrieve a line from hold and bring that party back into the
conference,
1. Press TRANSFER/CONFERENCE.
2. Press line button.
3. Press TRANSFER/CONFERENCE.
NOTE: If all the conference circuits are busy, you will not be able to
add a party to the conference.
To drop out of a conference call you initiated involving outside
lines (creating an unsupervised conference),
1. Dial
#
(lines remain lighted and in use until one or both outside
parties disconnect; when only one party drops out of an
unsupervised conference, the other party remains on hold until he
hangs up or the line is answered).
To rejoin an unsupervised conference between two outside lines,
1. Press TAP.
NOTE: Conference volume levels depend upon the quality of the
external lines.
6 – 2 LCD Speakerphone Reference Manual
GCA70–250