A single switch can control two lights through a wiring configuration called a "single-pole, double-throw" (SPDT) switch or a "three-way switch." This setup allows you to independently control two separate lights from a single switch location.
Here's a simplified explanation of how it works:
Power supply: The circuit begins with a power source, typically a breaker panel or a fuse box, which provides electrical power to the lights.
Switch: The switch used in this configuration is a three-way switch, which has three terminal screws. Let's call them A, B, and C.
Light connections: Let's assume you have two lights, Light 1 and Light 2, that you want to control using a single switch.
Light 1: Connect the positive (hot) wire from the power source to the common terminal screw (let's say, A) on the switch. Connect the positive wire from Light 1 to one of the traveler screws (B).
Light 2: Connect the positive wire from Light 2 to the other traveler screw (C) on the switch.
Neutral wires: Connect the neutral wires (typically white) from the power source, Light 1, and Light 2 together.
Ground wires: Connect the ground wires (typically green or bare copper) from the power source, Light 1, and Light 2 together.
- Switch operation: Now, when you flip the switch up or down, it toggles the connection between the common terminal (A) and either traveler terminal (B or C). Depending on the switch position, either Light 1 or Light 2 will receive power.
For example, if the switch is in one position, the common terminal (A) will be connected to traveler terminal (B), and power will flow to Light 1. If you flip the switch to the other position, the common terminal (A) will be connected to traveler terminal (C), and power will flow to Light 2.
In summary, a single switch can control two lights by utilizing a three-way switch configuration. The switch allows you to alternate the power supply between the two lights, providing independent control over their illumination.