CP-RIO3-04S Rear I/O module for CP305, CP307, CP308, CP3002 and CP3003 The CP-RIO3-04S is a Rear Transition Module designed for usage with CP305, CP307, CP308, CP3002 and CP3003 3U CompactPCI CPU board. The Module can be used to access the I/O's from the back of the system.