Dell Projector 2200MP - Manual (Page 21)

Degamma can be adjusted between 1 and 7. Default setting is 3 (Recommended).
Adjustment of the setting will change the color performance of the display.
Audio Menu
Audio
Volume
Press to decrease the volume.
Press to increase the volume.
Treble
Control the higher frequencies of your audio source.
Press to decrease the treble.
Press to increase the treble.