The D7 expansion module features 18 multi-coloured LED keys which can be programmed to provide a wide choice of functions, these keys can be can be easily configured and labelled via the phone's web interface or directly from the phone itself. The D7 has a large high quality display which provides a perfect visual interface. The D7 is simply connected via the USB cable and is ready to use. Up to three D7 expansion modules can be daisy-chained to add up to 54 function keys to your phone. The D7 Expansion Module is compatible with all Snom 7 and D7-series phones that have a USB port and is available in grey, black or white.