French engineer and former priest who invented the first mechanical optical telegraph, or semaphore. During the French Revolution, Chappe proposed a visual signaling line between Paris and Lille, near the frontlines of battle. The idea was to transmit messages using light between distant points. Chappe's brother, a member of the Legislative Assembly, strongly supported the concept. With the assembly's backing, the two constructed a series of hilltop towers equipped with a pair of telescopes, each pointed in a different direction, and a semaphore with adjustable arms that could assume seven clearly visible angular positions. The device was capable of displaying 49 combinations that were assigned to the alphabet and a number of other symbols. Using this system, it only took 2 to 6 minutes to transfer a message, whereas riding couriers would have needed 30 hours.