This is the mostly used switch on the bottom and top of stairs. Two way switches can appear difficult at first but if you take your time and study the images/diagram below, it ought to be pretty straight forward.
You have to a 2way light switch for this, they can be identified by looking on the terminals on the back of the switch.
E.g. com (common) L1 terminal and L2 terminal.
6 Diagrams – Click on the desired colours and difficulty to point out diagram
Brown sleeving or tape would of been placed on the wires as shown to show the blue is live.
_There are other methods of wiring a two gang two way switch but that is the most typical way and is the best by far_ – Jamie Vernon of Online Electrical Services LTD.
How to convert a 1 gang 1 way (single switch) to a 1 gang 2 way switch system?
For 1 gang two way switching you will need 3 core and earth cable to succeed in out of your new intended light switch to your old existing light switch via the best route. Click here for permitted cable routes.
Upon getting run the 3core + earth cables from A to B you will need to position it in the appropriate system. Click here for various back boxes and containment.
Below there may be 3 pictures listed per stage. The rationale being there is different cable colours and this is to ensure that your colour is listed here! (Only considered one of the photographs per stage will apply for you).