3 Way Wiring Diagram. You must completely forget about the notion of a switch being a simple openclosed circuit and look at the diagram of the circuitry of this modern alternative. The black hot wire connects to the far right switchs common terminal.
This cable consists of three cores - brown grey and black which are all Line colours and an Earth wire. If you are trying to troubleshoot a 3-way switch operation you will need to identify the function of each wire. Here coloured wires indicate the permanent mains supply to the boiler and programmer.
Wiring a three-way switch happens with the use of the 3 CoreEarth cable.
Other wires are shown in pale grey. All three switches are connected together by a three core and earth control cable. Take a closer look at a 3 way switch wiring diagram. Most likely to be found with wires in conduit.