AASTRA DT590 for MX-ONE User Guide EN - Manual (Page 88)

Settings
DT590 88
Key sound
When you have entered the Toolbox menu: º
Navigate to Sound & Alerts and then Key sound.
Use the Navigate key to select None, Click or Tone. Ь Ы
Press to confirm.
The selected key sound will be heard when a key is pressed.
Display settings
Backlight setting
When you have entered the Toolbox menu: º
Navigate to Display and then Backlight.
Use Navigate key to select On, Off or Automatic.
When set to Automatic, the backlight will switch off after a time
out, and switch on when you press a key or when you receive an
incoming call or message, or when an alarm sounds. Ь Ы
Press to confirm.
Contrast
When you have entered the Toolbox menu: º
Navigate to Display and then Contrast.
Use Navigate key to increase or decrease the contrast level. Ь Ы
Press to confirm.