This Standard applies to signalling and telecommunication apparatus which is installed in the railway environment. Signalling and telecommunication apparatus mounted in vehicles is covered by EN 50121-3-2. This standard specifies limits for emission and immunity and provides performance criteria for signalling and telecommunications (S&T) apparatus which may interfere with other apparatus in the railway environment, or increase the total emissions for the railway environment beyond the limits defined in the appropriate standard and so risk causing Electro-Magnetic Interference (EMI) to apparatus outside the railway system. Apparatus which complies with the emission levels of EN 61000-6-4 will meet the emission requirements of this standard provided that emissions from any d.c. power port are within the emissions limits specified for a.c. power ports. The immunity levels of EN 61000-6-2 will also be adequate except for the special case of apparatus as defined in note 1 of Table 1. This standard provides the immunity requirements for such apparatus. The immunity levels given for the apparatus will in most cases allow the apparatus to perform as intended in the railway environment (see note). The immunity level establishes a common reference for evaluating the performance of the apparatus when subject to interference resulting from direct exposure of the apparatus and associated cables to a radio frequency field, or by coupling of the interference from a remote source. If a port is intended to transmit or receive for the purpose of radio communication (intentional radiators. e.g. transponder systems), then the emission and immunity limits in this standard at the communication frequency do not apply. The standard does not specify basic personal safety requirements for apparatus such as protection against electric shock, unsafe operation, insulation co-ordination and related dielectric tests. The requirements were developed for and are applicable to this set of apparatus when operating under normal conditions. Fault conditions of the apparatus have not been taken into account. The requirements and test methods also apply to telecommunications and signalling data and power lines connected to the equipment under test (EUT). The frequency range considered is from d.c. to 400 GHz. No measurements need to be performed at frequencies where no requirement is specified. For products in the scope of EN 61000-3-2 or EN 61000-3-3, the requirements of those standards apply. Testing methods are given in the basic standards listed in Clause 2, Normative references. These specific provisions are to be used in conjunction with the general provisions in EN 50121-1. NOTE – The immunity and emission levels do not of themselves guarantee that the integration of apparatus will necessarily be satisfactory. The standard cannot cover all the possible configurations of the apparatus, but the test levels are sufficient to achieve satisfactory EMC in the majority of cases.