Why does my display illumination switch off?

If the handset is in the base station or the charging cradle, the display is dimmed. If you take the handset from the base/charger the illumination switched off completely after 60 seconds, if you not press any key.You can switch off or on this function with: 

 Menu Settings (8)  Display (3)  Backlight (4)
Select Without charger and press ( = on).
 

Press and hold (idle status).

NOTE: If the illumination is switched on outside the charging cradle, the standby time for the handset is considerably reduced!