Juniper Allegro CE Owner's Manual page 90

The Backlight tab allows you to select the length of time you want the
backlight to remain on while the Allegro is in an idle state. The
Backlight tab also allows you to set the brightness of the backlight.
The Options tab is used to set the display heater and contrast. The
heater options are Auto and Off. Auto is the default setting, which
turns on the heater automatically. Adjust the display contrast by
moving the slide bar left or right.
❖ Note: The display heater cannot be used if you are using alkaline
batteries. The Auto option is not available.
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