Aastra 9143i Series Administrator's Manual page 30

Keys Key Description
Programmable keys - Allows you to use the feature configured for that
key. You can program up to 7 keys with a specific function. By default, there
are no functions configured on the programmable keys (keys are
configured as "None").
Note: For more information about configuring the programmable keys 1
through 7 to perform specific functions, see Chapter 5, "Configuring
Operational Features" the section, "Softkeys/Programmable Keys/Feature
Keys/Expansion Module Keys" on page 5-142.
Mute key - Mutes the microphone so that your caller cannot hear you (the
light indicator flashes when the microphone is on mute).
Mute
*See the Aastra 9143i User Guide for more information about each of these keys.