This European Standard is applicable to single-pole and two-pole alternating current (a.c.) disconnectors, earthing switches and switches which are:- designed for indoor or outdoor fixed installations in tractions systems, and - operated with an a.c. line voltage and frequency as specified in EN 50163.NOTE 1 EN 50163 specifies the a.c. traction systems 15 kV 16,7 Hz and 25 kV 50 Hz.NOTE 2 As rails of a.c. traction systems are connected to earth and included in the return current path all phase to earth voltages will be within the tolerances as specified in EN 50163. Nevertheless phase to phase voltages are sometimes higher, e.g. in autotransformer systems.NOTE 3 The two poles of a switch can be connected in series to provide secure isolation (i.e. two breaks in series).