Motion sensor switches can automatically turn the lights on or off, or both. Occupancy switches turn the lights on when you enter the room; when you leave, the switch waits a preset time before turning the lights off automatically.

How does a sensor switch work?

An active sensor sends out sound waves that bounce off people and objects in the room and then returns them to the switch. If the returning waves identify a change in the pattern of the objects in the room—because someone has entered or is moving in the room—the sensor triggers the switch that turns on the light.

What is the purpose of a sensor light?

Light sensors measure illuminance, which can be used to measure more than the brightness of a light source. Because the illuminance decreases as the sensor moves away from a steady light, the light sensor can be used to gauge relative distance from the source.