AT&T 2255 - Manual (Page 15)

Conference Calling
1 If one handset is already on a call, you can connect the second
handset to the call by pressing
P.
2 Disconnect either or both handsets by pressing
P.
Mute
1 During a telephone conversation, mute the handset microphone by
pressing
. The other party
will by unable to hear anything on your
end. The screen displays
You will hear a reminder tone while the handset is muted. The
other party will not hear this tone.
2 To return to two-way conversation, press again.
13
TELEPHONE OPERATION
MIC MUTE