I use the phone with a Fritz box 7390. The phone is installed quickly and easily. Important to me was that it has access to a phone book Fritzbox. This works perfectly. However, it is not the internal phone book, but the Google Phonebook. So Individual are mobile, Fritz box and Grandstream always at the same level. MP3 ringtones and screen saver images can import and install via USB stick. From the browser interface of the phone I did not get. Install the latest firmware is required! The can be found on the manufacturer's site. The firmware file is installed on the browser Oberfläches. Under the menu item maintenance, upgrade and change the point upgrade via the pulldown menu of TFTP on manual upload and select the firmware. Those looking for a phone for its LAN Fritzbox, for I can recommend it.