Contact line (called CL) is a part of stable installations of electric traction, which are used for the quality supply of electric-traction stock with electric energy, and on the electrified railway lines. The electrification of the railways on the Serbian Railways begun in 1986 with mono-phase, alternating current system 25kV, 50Hz. Untill now, 2000 km of track was electrificated, which is 1/3 of all the railways built. In the Contact Line there are supporting frameworks and contact line equipment. Supporting frameworks are: catenary support, portal constructions. Contact line equipment is: catenary holder equipment, catenary, return cable, supply and sectioning equipment.

The contact line installed is catenary-compensated line for the speed under 120 km/h, in fact 160 km/h, and it was constructed according to the valid international and Yugoslavian regulations and standards.

Main characteristics: catenary type: catenary-compensated catenary height: min. 5,00m; 5,5m; max. 6,5m poligonation: ± 300 mm system height: 1 600 mm electric cable section: 150 mm2 rated voltage: 25 kV, 50 Hz maximum speed: 120 km/h; 160 km/h Contact line supply is done by electro-traction substations (EVP) 110 / 25kV 7,5 MVA, which are grouped along the railway, on the internal spacing of 60 km. Managing and controlling of the equipment and electric-traction installations is done form the Remote control Center, in which energy dispatchers are working. Maintenance of the contact line is being done through Contact line Maintenance Sections, which are located along the railway and maintain, generally, 120 km of contact line. The sections are equipped with guided vehicle, spare parts and tools. In this way they are enabled to do the regular and investment maintenance, interventions on extra events and disturbances and provide the works of other sections, on the electrified railway lines.