Installing A 3-way Switch With Wiring Diagrams - The Home Three-way switches require a three-wire cable: the power wire, the neutral wire, and the traveller or switch wire. The cable should also have a ground wire, or a total of four wires in the cable. The system also requires three-way switches.Installing a 3 · Method 2 · Power Through Switch · 5 - Canada · 4 - Canada Wiring Diagrams for 3-Way Switches - Ask the Electrician Eight 3 Way Switches Diagram Variations. First my easy to understand chart helps to identify the 3-way switch system for the application: 3-Way Switching provides switching from two locations . Diagram #1 above, shows the electricity source starting at the left 3-way switch. Wiring Diagrams for 3-Way Switches. 3-way switch diagram #2 above, shows the electricity source starting at the fixture.