Texas Instruments 4000M - Manual (Page 24)

Volume Control
To control speaker volume, use the following key combinations:
T
Ctrl-Alt-D - decreases the speaker volume
T
Ctrl-Alt-U - increases the speaker volume.
To control microphone volume, use Pocket Mixer, refer to Chapter 3 of this
manual. For more detailed information, refer to your TM4000 User's Reference
Guide.
Note: To prevent feedback from the internal microphone and speaker, select
Mute from Pocket Mixer.
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