7721 LV distribution (0) The distribution of low voltage electricity from and including the building main switchgear panel to and including all distribution boards and sub-distribution boards 7722 General LV power distribution (2) Sub-circuit power installations from sub-distribution boards, terminating with socket outlets or connection to appliances and other power users 7723 Special low voltage power distribution (0) The distribution of low voltage electricity to socket outlets and other user points 7724 Extra low voltage supply (0) The distribution of extra-low voltage electricity from local transformers to specialised equipment 7725 Non-standard frequency power (0) The distribution of power at a frequency greater or less than the standard power supply including protection and earthing systems 7726 Emergency/standby power (0) The distribution of emergency electricity from the site electricity generating plant or from standby batteries and associated charger, to distribution boards and sub-distribution boards, to changeover from the supply authority's supply to site-generated electricity and/or standby battery supply, in the event of failure of the authority's supply 7727 Power factor correction (0) Power factor correction unit (PFC) to control the electrical installation power factor to usually 0.95 or higher lagging power factor under all load conditions.