Optical switches (also known as opto-switches) are electronic switches that are activated by light. They are useful for triggering events, detecting the presence of objects and measuring their position or distance. Optical switches are commonly used in industrial automation and safety systems, as well as consumer electronics. Transmissive optical switches use an infrared beam that is transmitted from an LED and reflected off an object or surface. When the beam is blocked or interrupted, the optical switch is triggered. Photo IC output optical switches are used for position sensing and measuring changes in light and shadow. They include a light sensor, usually a photosensitive transistor, and use a light source, usually an LED. When the light hits the phototransistor, it generates a voltage that is used to turn on the switch. This type of switch is often used in consumer electronics and industrial machine controls.