This European Standard gives general guidelines and recommendations to ensure interworking between HBES devices made by different manufacturers. It also contains design guidelines for the design of Functional Blocks and new datapoint types, the building blocks of HBES interworking. In this way, the standard can be used as a basis to design application specifications relative to an Application Domain. If designed and supported by a large group of manufacturers, such application specifications will ensure to end customers a high degree of interoperability between products based on the HBES Communication System of different manufacturers. This European Standard is used as a product family standard. It is not intended to be used as a stand alone standard.