Altina A600 - Manual (Page 15)

3. System Settings
Your device is supplied with default settings. You may also customize the settings
to suit your personal needs. Once you change settings, your new settings will
remain until either you change them again, or until battery cutoff switch is turned
off and then back on again, which resets the unit to factory defaults.
3.1 Using System Settings
Tap the Setup button on the Main screen.
The Setup screen contains six buttons as shown below. The following sections
describe these six buttons and their functions.
3.2 Brightness
1. Tap Setup on the Main screen.
2. Tap the Brightness button on the Setup screen.