Optical telegraphy refers to techniques of transmitting messages across distances by visual means ( News). Its history runs from forms of simple signaling (e.g. beacons) to large-scale, systematic networks of mechanical telegraph apparatuses. The invention of the telescope in the 17th century inspired the first discussions of long-distance communication. In a 1616 treatise, Franz Kessler proposed using a telescope to read code numbers off a “number plate” (“Ziffer Täffelein”) at a distance […