The D3 expansion module features 18 multi-colour 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 D3 has a large high quality display which provides a perfect visual interface. The D3 is simply connected via the USB cable and is ready to use. Up to three D3 expansion modules can be daisy-chained to add up to 54 function keys to your phone. The D3 Expansion Module is compatible with the Snom D315, D345 and the D765 and connect via the phones USB port.