Symbol Technologies MC9000-K - Manual (Page 483)

Keypad Maps B-73
Table B-17. MC9000-S: 28-Key Functions
Local Function Key Sequence
Display Backlight On/Off <Func><#>
Keypad Backlight On/Off <Func><0>
Contrast + <Func><1>
Contrast - <Func><4>
Volume + <Func><3>
Volume - <Func><6>