Gentex Corporation manufactures automatic-dimming rear-view mirrors, camera-based driver assistance systems, and the HomeLink Wireless Control System for the global automotive industry. The company also provides commercial smoke detectors and signaling devices to the North American fire protection market, as well as dimmable aircraft windows for the commercial, business and general aviation markets. The company is based in Zeeland, Michigan and was founded in 1974. Their mirrors use electrochromism to dim in proportion to the amount of light reaching them from following vehicles' headlamps. The mirrors are available with added electronic features. About 98 percent of the company's net sales are derived from the sale of auto-dimming mirrors to every major automaker in the world.