The harmonized standard EN 50121-3-2

The EN standard 50121-3-2 regards electromagnetic compatibility aspects of the equipment installed on board of railway vehicles.

In it are specified the requirements that these products must satisfy in terms of emissions and immunity, taking into account the railway environment and interference generated by other equipment present on board.

The EN standard 50121-3-2 It is prepared and issued by CENELEC (European Committee for Electrotechnical Standardization) which it is the European Committee for Electrotechnical Standardization.

Field of application: the rule applies to the aspects of emissions and immunity of electromagnetic compatibility for electrical and electronic equipment intended to be used on rolling stock and with a frequency range up to 400 Ghz.

Examples of equipment for installation on railway vehicles are:

  • devices for recording and storing data (data logger);
  • Emergency telephones;
  • signaling display;
  • speakers.


The railway infrastructure has an electromagnetic environment complex formed by many signaling systems, traction, telecommunications and radio communications.

The electromagnetic compatibility (EMC) between electrical and electronic systems is an essential requirement for the safe and reliable operation of the equipment. It is all too evident that the interference caused by traction systems may disturb the signaling equipment, with potentially dangerous consequences.

The main problem of electromagnetic compatibility environment rail is the differentiated function of the rails. Originally the rails were solely a mechanical guidance system, but the advent of electricity and technological growth have made the railway infrastructure a complex system in which interact with different equipment. The presence of technologically advanced equipment and the "historical" makes the problem of interference an extremely important issue.



The specific harmonized rules for the rail sector to EN 50121 that regulate the electromagnetic compatibility aspects both within the railway environment both between the rail and the external environment.

These standards are directly referred to by the harmonized standard for i to test 50155, concerning the environmental stresses typical of the railway environment. This together with the norm for i to test 45545, concerning fire behavior, are the main specific rules of the railway environment to which electronic equipment installed on trains must comply, subways and trams.

The family of EN standards 50121 It is divided into 6 parts covering different areas:

  • ON 50121-1 Generality
  • ON 50121-2 Emission of the whole railway system to the external environment
  • ON 50121-3-1 Rolling stock - Train and complete vehicle
  • ON 50121-3-2 Rolling stock — Equipment
  • ON 50121-4 Emission and immunity of the signaling and telecommunications apparatus
  • ON 50121-5 Emission and immunity of equipment and fixed power supply installations

At electrical and electronic equipment installed on board the norm EN applies 50121-3-2 that takes into account both the internal environment railway infrastructure is the external environment.

The standard also considers any interference from portable radio transmitters used on board, such as walkie-talkie.

The goal of the standard is to define the limits and the test methods to meet emission and immunity requirements in relation to conducted and radiated disturbances.

The emission requirements are intended to ensure that the noise generated by the apparatus during its normal operation do not exceed a level that would prevent other equipment to function properly.

Similarly, the immunity requirements are intended to ensure that the devices installed on board are not too susceptible to disturbances generated by other devices.

The verification of the railway equipment can be complex for certain parts, so it is good to rely on an expert workshop as Sicom Testing that, thanks to his many years of experience in to test 50155 and to test 45545 , It can provide all the necessary support to assess and verify the electromagnetic compatibility aspects of these products.

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2 comments on "Harmonised standard EN 50121-3-2”

  1. hi I'm a ustif official, I have to approve with NOT the installation of magnetic validators on some tram cars .
    as you advise me to proceed ?

    • Good morning.
      In this case it is necessary to hear the indications of a notified body for the railway interoperability directive. Preferably the same one who has already certified the tram.
      Greetings from Sicom Testing


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