Another way to wire a three-way switch is when supply comes at the switch, goes to the fixture, and terminates at the other switch. In this wiring diagram, the fixture is connected to the switches with three-wire cables. You can create a detailed diagram like this one or create a simple outline of the layout.
In building wiring, multiway switching is the interconnection of two or more electrical switches to control an electrical load from more than one location. A common application is in lighting, where it allows the control of lamps from multiple locations, for example, in a hallway, stairwell, or large room.
In contrast to a simple light switch, a single-pole, single-throw (SPST) switch, multiway switching uses buttons with one or more additional contacts, and two or more wires are run between the switches. When the load is controlled from only two points, single-pole, double-throw (SPDT) switches are used. Double pole, double throw (DPDT) switches allow control from three or more locations.
In alternative designs, low-voltage relay or electronic controls can switch electrical loads, sometimes without the extra power wires.