Switches open and close electrical circuits, allowing power to flow through lights and appliances. At one time, they were pretty simple—just a toggle you flipped on and off. But things have changed.
Switches should match the amperage and voltage ratings for the electrical circuit they serve. If your home has aluminum wiring, be sure the switches attached to that wiring are designated “CU-AL” for compatibility—otherwise, they can present a fire hazard.
The simplest and most common light switch is actually referred to by hardware dealers and electricians as a “single-pole light switch.” With a single-pole light switch, flipping the lever up completes the circuit, turning lights or appliances on, and flipping it down breaks the circuit, turning lights or receptacles off.
A single-pole switch has two brass terminal screws on the side that receive the black wires of the circuit—one black wire from the power source and the other going to the light(s). (The number of terminal screws identifies the type of switch.) Modern single-pole switches also have a green grounding screw (not shown) that connects to the circuit’s ground wire.
The type of switch that will operate hallway lights from either end of the hallway is called a three-way switch; it has an extra terminal.