Display backlight, Display backlight -3, The resolution is 240 x 320; see – Hand Held Products DOLPHIN 7600 User Manual
Page 19: Display, Backlight

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Display Backlight
The touch screen display has a backlight that is programmed to turn off after a specified period of time that the device is idle.
To change the default timeout parameters, tap Start > Settings > Control Panel > Display > Backlight tab.
To adjust the intensity of the backlight, tap Start > Settings > Control Panel > double-tap Backlight .
Move the slider to adjust the backlight.