Explanation

Lighting circuits often use a system where each lighting point is fed with a Live, Neutral and Earth (CPC). These are then extended to give the next light its Live, Neutral and Earth (CPC). Each light is then switched on & off using a switch or combination of switches that are appropriate to that lights use.

The simplest switching arrangement is the one way lighting system where a cable usually a twin & CPC is taken from the light fitting to the switch. This cable is then connected as follows.

• The brown is connected to the permanent live at the light fitting and the common or C terminal in the light switch.
• The bare core has green & yellow sleeving attached to it and connected to the earth terminal at the light and at the light switches backbox and or frontplate if decorative metal.
• The blue is connected to the switched live terminal in the light fitting (ceiling rose) which connects to the 2 core flex going to the lamp holder whilst at the switch it is connected to the L1 terminal at the light switch. As blue indicates a neutral and we are now using the blue core as a switched live we indicate this change of use by applying a small piece of brown sleeving over the blue core at both ends of the cable (note the brown dots in the interactive tool).

NB One way switches have terminals marked Common and L1 and switching the switch switches its mode from open to closed. There is a slightly more complex switch known as a 2 way switch that has common and L1 and L2 terminals that is slightly more expensive that can be used for both 1 way and 2 way switching purposes.. If a 2 way switch is to be used the wires should connect between Common and L1 again and attention paid to a marker in the switch that says TOP. Whilst the switch will still work if you use Common and L2 or fit the switch upside down it may cause confusion to users as switches with the bottom part of the switch flush to the switch plate indicates on in the UK on 1 way switches.

NB CPCs are not shown in the interactive tools for clarity (plus drawing green/yellow striped lines is ricky in this software).