New IEEE Standard - Inactive-Reserved. A serial highway (SH) system using byte-organized messages and configured as a unidirectional loop, to which are connected a system controller and up to sixty-two CAMAC crate assemblies, is defined. In the primary application, the controlled devices are CAMAC crate assemblies with serial crate controllers that conform to a defined message structure. In other applications, some or all of the controlled devices connected to the SH can be equipment that conforms to a subset of the full specification and is not necessarily constructed in CAMAC format or controlled by CAMAC commands.