Optical telegraphy. Historical illustration of an optical (also called visual or aerial) telegraphy system used by the British in the early 19th century. Before the advent of electrical telegraphy using wires, a number of semaphore or shutter-type telegraph systems were developed to send signals. Opening and closing the shutters according to a set code would transmit messages between telegraph stations that formed a chain between cities. Artwork from 'Electricite' (1911) by Max de Nansouty, part of the 'Les merveilles de la science' series of 1867-1891 by Louis Figuier.