RME offers several Expansion Boards, that add more or other I/O ports to the internal cards of the Hammerfall, HDSP, HDSPe and DIGI96 series. The OPTO-X replaces the standard coaxial MADI I/O of the HDSPe MADI FX by an optical MADI I/O. The AI4S-192 AIO and AO4S-192 AIO add additional analog inputs and outputs of true studio quality to the HDSP 9632 and the HDSPe AIO. The Word Clock Module WCM adds a word clock input and two outputs in professional quality to the HDSP 9632, HDSPe RayDAT and the HDSPe AIO.