pre-1976: solid green). Steel-wire armoured Steel wire protected cable, mandatory for outdoor or buried use unless equivalent protection provided via trunking. Trunking Protective conduit, typically made of plastic or metal, used to protect and hold cables, and allow access and maintenance, as they pass through the installation premises. Meter tails (or, tails)Separated core cables used to connect the incoming power supply to a premises with the distribution board. Typically in a domestic environment, connects the electricity meter (which is owned by the supplier and treated as the incoming source) to the consumer unit. Twin/2, 3 or 4 core and earth Flat cable, usually insulated by a polyvinyl chloride sheath, used for fixed wiring. The name comes from the fact that it contains line and neutral conductor cores with individual insulations (twinned), and an uninsulated earth core. 3- and 4- core are identical but contain further conducting cores, each individually insulated. This type of flat cable is a type of cable which is used in houses (although out of sight) and has a standard colour of grey and it supplies sockets, lighting and appliances etc. Voltage and phases Low voltage Where the peak voltage does not exceed 600 volts. In practice this means DC supplies that do not exceed 600 volts and AC supplies that do not exceed 425 volts. Almost all domestic; light commercial (e.g., offices) and industrial (for three phase machinery) power is low voltage for regulation purposes. High voltageAny voltage in excess of low voltage; usually found in industrial processes and electricity transmission and distribution networks. Extra-low voltage (ELV) 50 V AC or 120 V ripple-free DC, or less. Separated extra-low voltage (SELV) Extra-low voltage system that is also electrically isolated. Single phase, 3 phaseAt low voltage electricity may be supplied by the distributor (DNO) as either single or 3 phase. A single phase supply will comprise a single live conductor and a neutral conductor. A 3 phase supply will comprise three live conductors each pair with a phase separation of 120 degrees and (optionally) a neutral conductor. A separate earth conductor will normally be supplied in both cases but may not be present depending on the connection type. Earthing (bonding) Bonding (including main bonding, supplementary bonding and equipotential bonding) Connection made to earth, for protective purposes, either for individual components, for other metal objects in the premises (such as gas, water, or oil piping), or for the