This European Standard applies to the on board and on board to ground communication services, i.e. it covers the data communication using digital interfaces: between functions implemented within the EMS; between EMS function and other on board subsystems; between EMS and ground communication services. The on board data communication services of the EMS are covering the data exchange between functions of the EMS and the data exchange between EMS and other on board units, where data is exchanged using a communications protocol stack over a dedicated physical interface or a shared communication network. The on board to ground communication services are covering the wireless data communication between the DHS and the on ground server. Furthermore, this document includes conformity assessment requirements.