AT&T 7406BIS - Manual (Page 8)

Mute button For turning off the microphone of the built-in speakerphone
or the handset so that the caller cannot hear you. Note: If
your voice terminal is set for the Speaker (listen only) feature,
pressing the Mute button will affect only the handset.
Feature button For accessing a feature, labeled with a feature name and
equipped with a green light.
Transfer button For transferring a call to another voice terminal.
Hold button For putting a call on hold.
Shiftable feature For accessing each, two features, labeled with feature names;
buttons features on the top of the label are accessed when [
Shift
] is
activated.
Speaker volume- For adjusting the volume of the speaker or the built-in
control button
Dial pad
Volume control (under
voice terminal)
speakerphone.
For dialing the telephone numbers and accessing features
(12-button pad).
For adjusting the volume of the tone ringer.