In telecommunication systems with peripheral equipment powered directly from mains, the system is earthed via all protective conductors (PE) and via the functional earth conductor (FE). This arrangement fulfils the requirements against electrical shock. But for functional purposes a special earth system has to be provided in such a way that between earth reference conductors no voltage difference occurs which disturbs the prober system function. Therefore, additionally to the earthing arrangement for electrical installation of buildings prescribed in the IEC publication 364-5-54 one or more of the following requirements have to provided. 1. Connection of a telecommunication system to the supply system (mains) with separated protective conductor (PE) and neutral conductor (N). 2. Application of a local supplementary equipotential bonding 3. Installation of a reference earth network 4. Using of combined functional and protective conductors (FPE) DIN VDE 0800, part 2 “Telecommunications: Earthing and equipotential bonding” prescribes the requirements for these earthing arrangements.
