AT&T Definity ISDN 7507 - Manual (Page 7)

Call appearance/feature
buttons
Redial button
Select button
Mute button
Speaker button
Volume button
Transfer button
At least 2 of these buttons are devoted to handling
incoming and outgoing calls (call appearances) and are
labeled with an extension number; the remainder are
call appearances or access features (feature buttons)
and are labeled with a feature name. Each button has a
red light and a green light.
For redialing the last voice number dialed.
Used to access a second level of features on the

Redial
, 
Drop Test
, 
Transfer Clock
,
and

Conference Ring

and
secondary feature buttons.
Press to have a conversation at your end without the
person at the far end hearing. Mute works with both
the handset and the Speakerphone.
If your terminal is programmed with a Speakerphone
or SPOKESMAN® loudspeaker, this button is used to
turn the speaker on or off.
When on a call, used to decrease or increase the
volume of the handset speaker, Speakerphone
loudspeaker, or the SPOKESMAN loudspeaker. When
not on a call, used to decrease or increase the ringer
volume.
For transferring a call to another voice terminal.