In building wiring, multiway switching is the interconnection of two or more electrical switches to control an electrical load (often, but not always, lighting) from more than one location. For example, this allows lighting in a hallway, stairwell, or large room to be controlled from multiple locations. While a "normal" light switch needs to be only a Single Pole, Single Throw (SPST) switch, multiway switching requires the use of switches that have one or more additional contacts and two or more wires must be run between the switches. When the load is controlled from only two points, Single Pole...