Wiring two way switches for lighting
(See this page for the 2004 changes in colours)
Sometimes, a light circuit needs to be controlled from two positions - across a room, at each end of a corridor or at the top and bottom of a stairway. Such lighting circuits are commonly known as 'two way' light circuits and are quite easy to install.
The two switches need to be of a 'change-over' type. These have three terminals, a common terminal and one for each of the switch positions.
The cable to the switches needs to be 4 core lighting cable, 3 insulated cores and earth.
The circuit is shown below, the live feed is fed through both switches to the light and the switches are cross connected so that when a switch is operated, the state of the light is changed.
Because of the number of wires involved, it is easier to use a separate junction box (minimum of 6 terminals) rather than trying to make the connections in the ceiling rose.
An alternative method (contributed by Mike Pheysey)
Where space in the conduit to the switch allows, a simpler circuit can be used, this removes the need for the 5 terminal junction box but requires both a three core and a four cable to be connected to one of the switches. The circuit is shown below (thanks for your contribution mike):