IEC 61851-1 is the general part of the electric vehicle conductive charging system series. It defines the architecture of a charging system that transfers energy to a vehicle through a conductive connection, and it establishes the vocabulary and the interface requirements that all the subsequent parts build upon. Central to the document are the charging modes, which are distinguished by the power source, the cable arrangement and the communication between the vehicle and the supply equipment, and which range from a domestic socket outlet with a mode 1 or mode 2 connection through to a dedicated mode 4 d.c. charging station. The standard defines the signalling that is exchanged over the pilot conductor between vehicle and charging point, the control functions that guard against the connection of a vehicle with an incompatible supply, the protection against electric shock that the interface must provide in both normal and fault conditions, and the requirements for the connectors and for the vehicle inlet. Requirements for the supply equipment and for the on-board equipment are set out separately so that each may be tested independently.