CP-RIO3-923 Rear I/O module for CP3923 - Managed Layer2/Layer3 3U CompactPCI Switch The CP-RIO3-923 is a Rear Transition Module that enables access to the CP3923 management and switch uplink ports. Management access is either possible via a serial RS232 interface or Gigabit Ethernet. For both, a RJ45 connector is provided. Furthermore the RTM provides access to eight Gigabit Ethernet ports.