Breaking down the Wiring Diagram: Current enters through the black wire towards the 1 st switch box, attached to the common terminal.; Down position of the 1 st switch means exiting through the red wire and then visiting through traveler terminal into 2 nd switch.; Down position of the 2 nd switch means again exiting but this time through 3 way switch common wire black and enters the light.. The diagrams for 3-way switch wiring I broke down into the following sections (see below): Light after switches. The power source is coming to a light switch first. Light before switches. The power source is coming to light fitting first. The electricity source and light fixture are connected to the same switch.
Three-way switch wiring diagram with the LINE and the LOAD inside separate switch boxes. LINE power is delivered to the first switch by using a two conductor cable with a bare or green equipment grounding conductor. The LINE wire is connected to the "Common" terminal on the 3-way switch. A three conductor cable goes from one switch box to the.. A 3-way switch allows you to turn a light on or off from two different switches. 3-way switches are useful for large rooms with multiple entrances but require a bit more wiring than a standard, single-pole switch. The wiring method will depend on whether your power goes to the switch first or the light first.