The invention relates to a method for transmitting a data telegram from a non-real-time domain to a real-time domain, comprising the following steps: generation of a non-real-time data telegram comprising a useful data zone, the data telegram containing a real-time or a non-real-time identifier in addition to a data telegram identifier (identifier i) in the useful data zone thereof when the real time identifier is provided; monitoring of the non-real-time data telegram for the presence of a real time identifier by the coupling unit if the real-time identifier is provided; transmission of the useful data and real-time identifier (identifier i) from the useful data zone of the non-real-time data telegram to a user interface of the coupling node; storage of the useful data in a storage zone of a communication memory which is associated with the identifier.