This Part 1 of the European standards series EN 50121 outlines the structure and the content of the whole set. It specifies the performance criteria applicable to the whole standards series. Clause 4 provides information about the EMC management. This part alone is not sufficient to give presumption of conformity to the essential requirements of the EMC-Directive and is intended to be used in conjunction with other parts of this standard. Annex A describes the characteristics of the railway system which affect electromagnetic compatibility (EMC) behaviour. Phenomena excluded from the set are Nuclear EM pulse, abnormal operating conditions (e. g. fault conditions) and the induction effects of direct lightning strike. Emission limits at the railway system boundary do not apply to intentional transmitters within the railway system boundaries. Safety considerations are not covered by this set of standards. The biological effects of non-ionising radiation as well as apparatus for medical assistance, such as pacemakers, are not considered here.