installation (or some part of it) as a whole. Earth/ground rod A long rod placed into the ground, bonding, with low impedance, the installation to earth potential. Usually made from copper-clad, galvanised or stainless steel or copper, for corrosion prevention. There are other types of earth bond, such as: earth plate, earth mesh, or earth ring. Circuit terminology Circuit Means used to connect a distribution board or consumer unit to devices that will receive power from it (typically cable and accessory components). Final circuit Circuit that supplies electricity to end-user devices (lighting, heating, sockets, appliances, etc.). Radial and loop A circuit where each load is supplied by a single cable; i.e., the cables branch, or radiate, outwards from a single supply point. Loop wiring is radial wiring in lighting circuits where junctions are made at ceiling roses with line and switched line wires. Ring, or ring final circuit (RFC) A ring circuit is a UK standard means for wiring domestic and other light commercial premises, not often seen elsewhere in the world; in effect it is a radial circuit whose final termination is made back to the originating distribution board, rather than at the last outlet or device serviced. De-energized circuit Circuit that is isolated from power and not at a potential different from earth. Note the difference to permit to work. Spur A branch supplying a side-socket or outlet, especially from a ring circuit. Wiring colours Conductor colours The standard wiring colours in the UK are () the same as elsewhere in Europe and follow international standard IEC 60446. This colour scheme had already been introduced for appliance flexes in the UK in the early 1970s, however the original red/black colour scheme recommended by the IEE for fixed wiring was retained until 2006, albeit with change to a green/yellow striped earth in 1976. As a result, the international standard blue/brown scheme is as of 2006 found in most appliance flexes. In fixed wiring, the blue/brown scheme is only found in newer (post-2004) installations, and the old IEE red/black scheme is likely to be encountered in existing installations for many more decades. The standard colours in fixed wiring were harmonised in 2004 with the regulations in other European countries and the international IEC 60446 standard. For a transitional period (April 2004 – March 2006) either set of colours were allowed (but not both), provided that any changes in the colour