The D7 expansion module features 18 multicolor LED keys which can be programmed with all functions available known to Snom phones like line, speed dial, busy lamp field, presence indication, and many more. 18 highly configurable self-labeling LED keys High-resolution black & white display with backlight Daisy chain up to 3 modules  Plug and play Power supplied by phone via USB port 

18 Configurable MultiColour LED keys, High-Res Graphic Display, Daisy-chain up to 3 modules