Yes, but you will have to do a "Firmware restore" first.
Follow the steps below to do a firmware restore.
- Remove power from the unit.
- Hold the MENU/settings-button (middle button on top row) during while you power on the unit.
- Keep holding the button until you see the "Recovery menu" in the display, then you can release the button.
- Select option 3 (by pressing digit 3) "Firmware restore".
- Let the unit restore factory firmware it could take up to 3 minutes.
- After the process is done, the unit will reboot with factory firmware.
(same for Konftel 300IP and Konftel 300IPx)