AT&T MERLIN LEGEND Installation & Maintenance Manual page 636

General Feature Use
Follow these general instructions to use features on MLX, analog
multiline, and single-line telephones. To use a feature:
press a dedicated feature button
press a programmed button
dial a feature code
select a feature from the display (MLX display telephones
only)
Dedicated Feature Buttons
All multiline telephones have a group of dedicated feature
buttons that are programmed and labeled at the factory. The
functions of these buttons, which include Conference, Transfer,
and Speakerphone, cannot be changed. Press the button for
the feature you want to use.
Programmed Buttons
See Appendix E, "General Telephone Programming," for more
information on programming features onto line buttons.
General Feature Use F-1