A head station including at least two identical processing units supplied respectively with at least one identical input datastream in order to generate an output datastream, and an output bus system connected to the processing units for the exchange of output datastreams and status data generated in each of the processing units is provided. Additionally, within the head station, several decision circuits connected to the output bus system are provided for the selection of the output datastream to be transmitted in each processing unit in each case to a transmitter system.