This European Standard defines the mandatory and optional requirements for the medium specific Physical and Data Link Layer of Radio Frequency for HBES products and systems, a multi-application bus system where the functions are decentralised, distributed and linked through a common communication process. This European Standard is used as a product family standard. It is not intended to be used as a stand-alone standard. Data Link Layer interface and general definitions, which are medium independent, are given in EN 50090-4-1.