This Technical Specification provides the requirements for compatibility of systems defined and good practice for three phase AC 400 V/50 Hz shore (external) supply systems. It focuses on describing the defined interfaces regarding electrical power supply in stations, depots/workshops and stabling points into the rail vehicle. This Technical Specification provides recommended characteristics of power supply and its connectors. The electrical characteristics relate to 3 AC 400 V/50 Hz. Sensing of phase rotation is outside the scope of this standard but it is assumed that phase sequence between the external supply and the railway vehicle is synchronised. Annexes have been provided for National Systems, using three phase 400 volt / 50 Hertz shore supply systems, where full information is available.