Cortelco 2757 User Manual
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2. Press ‘Up’ or ‘Down’ until ‘3. Settings’ is selected, then press ‘Select’.
3. Press ‘Up’ or ‘Down’ until ‘3. Contrast’ is selected, then press ‘Select’.
4. Press ‘Up’ to make the displayed messages darker. Press ‘Down’ to make the displayed
messages lighter. Press ‘Save’ keep the new settings.