Method of operating a data bus system and a transmitter station

A data bus system, comprising a plurality of stations (10-15), including at least two transmitter stations (11, 12, 15), each transmitter station (11, 12, 15) being switchable to an active mode in which the relevant transmitter station (11, 12, 15) digitally transmits a respective data stream, bus means (17, 18a, 18b) which interconnect the stations (10-15) of said plurality, resource control means (11) for controlling which transmitter stations (11, 12, 15) simultaneously operate in the active mode. The resource control means (11) are arranged to assign different data stream identifiers, via the bus means (17, 18a, 18b), to different transmitter stations (11, 12, 15) wishing to operate in the active mode. The transmitter stations (11, 12, 15) are arranged to subdivide their own data stream into message frames (42), to digitally transmits each time a frame (42) per period (40) and to provide each message frame (42) of its respective data stream with the identifier assigned to the relevant transmitter station (11, 12, 15).