LEDs, (Light Emitting Diodes) are small semi-conductor devices which emit bright light in a range of colors.  They are available in a variety of sizes and brightness levels, and are very energy-efficient. They can be engineered for extended battery life through the use of PIR (passive infra-red), also known as a motion sensor, or through sound detecting sensors to achieve long shelf life requirements.

LED light arrays can be diffused to create an even lighting area instead of single points of light, and can be animated in sequence to create a sense of motion.  LEDs can be used in Edge-lit and Back-lit displays. The edge-lit display version is lighter and thinner, but typically offers less brightness than a back-lit diffused  LED signs.  LED displays are ideal for use in areas where ambient light mandates a higher brightness, such as the new Domino's signs below: