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 changeover type. These have three terminals, a common terminal and one for each of the switch positions. 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 with minimum of 5 terminals rather than trying to make the connections in the ceiling rose.

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.

In case of two-way lighting circuit all connections between cables are made at switch contacts. Adding more switches can be easily done. Use a special intermediate switch that has four terminals. This breaks into the red and blue cores and either connects them as normal, or connects incoming red to outgoing blue, and vice versa. With care, yellow core can be left untouched. So a connector block need not be used here either.

Tips:

• Arrange the wiring so that the lamp is off if all switches are up. This makes it easy to be sure that the lamp holder is not live when changing bulbs.
• As with all wiring, use green and yellow sleeving around bare earth conductors.
• As with all wiring, put a ring of red tape around exposed cable cores which are not red, but are nevertheless live: yellow and blue cores of triple and earth cable, and black cores of twin and earth switch feeds.