The "Media Oriented System Transport" bus (MOST) is a serial bus system for the transmission of multimedia data. Audio, video, voice and data signals are transmitted via optical fibres or electrical conductors. In motor vehicles, the MOST bus is used for multimedia applications and is nowadays used by almost all car manufacturers. From a physical point of view, the network is always a ring topology, although in practice other structures are possible. With the UniTrain course, a self-contained MOST system with optical fibre can be put into operation. Likewise, if several modules are present, it is possible to expand the MOST network accordingly and realise a complete ring topology.