Abstract: A characteristic message exchange procedure is performed by a set of contler units at separate stations and of functionally identical design. The combination of a controller unit and a utilization unit that characterizes the application of the station constitutes a complete station. Among other things, the controller units provide sequencing of the transmitting privilege among the stations one by one. All message data are classified into four basic message models representing the applications of the stations. The stations are interconnected by a single common transmission channel and the controllers are equipped to be sensitive to only four basic message models. No central control unit is required for monitoring transmissions between stations. All active stations receive all messages essentially simultaneously.