AT&T 7406BIS - Manual (Page 7)

Starting at the upper left of Figure 1 and continuing clockwise:
Handset For placing and answering calls. In most cases, you must lift
the handset (go off-hook) before you can use a feature. Also
known as the receiver.
Call appearances/
feature buttons
Display
Select Ring
button
Shift button
Display-viewing
adjustment
Speaker button
For handling incoming and outgoing calls (call appearances),
labeled with extension numbers. For accessing features
(feature buttons), labeled with feature names.
For showing information (2-line, 48-character display).
For accessing the Select Ring feature.
For accessing the top-labeled features on shiftable buttons.
For adjusting the viewing angle of the display.
For accessing the speaker or the built-in speakerphone and
microphone combination. Note: Your voice terminal can be
set for either the Speaker (listen-only) feature or the
Speakerphone (listen and talk) feature. Check with your
System Manager to see how your Speaker button is to be
used.