To charge the battery, insert the handset into the charging shell with the keypad facing forwards. 

Caution:  Only use the approved C39280-Z4-C373 power supply unit provided for operating the charging shell.

The charging status is indicated by the charge status display. This flashes during charging: 

Note:    Initial charging: Charge the battery for at least 16  hours, regardless of the charging status icon. Without replacing it in the charging shell, use the handset until the "battery low" beep is heard. This action aligns the charge status display with the battery operating times. To attain full operating and charging times (): Without replacing it in the charging shell, use the handset until the "battery low" beep is heard. For future charging: you can place your handset in the charging shell each time it is used. Charging is electronically controlled which ensures that the battery is charged optimally.