Settings > Display and Backlight > Display Backlight

Display Backlight
The display backlight on the telephone can be adapted according to individual work place requirements.
automatically: As soon as a key is pressed, the receiver is picked up or the telephone is called, the backlight is switched on (brightness max.) and remains in this state afterwards for short transitional period. Otherwise, the backlight remains on a standby level (brightness min.).
Permanently switched on during a call: In addition to the times available in the automatically selection, the backlight remains switched on for the entire duration of a call and afterwards for a short transitional period.
Proceed as follows:
Using COMfortel Set (page Settings/functions > Display, list field Display backlight)
Using the telephone (menu settings > display > display light)

COMfortel 1400 - Firmware V2.2 - COMfortel Set V3.16 - Advanced Information V07 02/2019