The Arcon Communications Node TRAM (or CommNode) is a transputer which routes ct.packet protocol messages between various other transputers. Two flavors of CommNode program run in the CommNode TRAM. The simpler generic communications node may be used between any four transputers which speak standard ct.packet protocol (for example it may be used to multiplex other CommNodes). The specialized optical communications node program (depicted) is used between the NEXUS TRAM, and SEQUENCER TRAM, to route CCD control information from the user to the CCD, and between the output of the CCD (and other hardware, such as the VTT card) and the NEXUS TRAM to format and return data and diagnostic information.