Visual Telegraphy

Foundation of Communication > Visual Telegraphy

Telegraphy is the long distance transmission of written messages without physical transport of letters. The first telegraphs were Visual Telegraphs, they used visual signals such as smoke signals and beacons. These have existed since ancient times, but they were unreliable and very susceptible to being garbled in transit.

In 1793, a Frenchman, Claude Chappe invented the Semaphore Telegraph, which is a visual signaling system. Chappe’s telegraphs were installed on towers built roughly 10 to 15 km apart. Each apparatus was composed of 2 movable wooden arms connected by a crossbar. The operator on the tower moved the arms and crossbar to different positions and angles to indicate different letters and symbols, which were observed by the operator of the next tower with a telescope. He then made the same signals to the next tower. In this way, the message was transmitted from tower to tower.

This first Chappe’s Semaphore Line was established between Paris and Lille. In August 1794, Chappe’s semaphore system delivered to Paris the message of the capture of Condé-sur-l’Escaut from the Austrians in less an hour. This success led to more semaphore telegraph lines being built. The semaphore network in France was the first telecommunications network in Europe.

The six-flap Visual Telegraph, exhibited in the Museum, is a replica based on the design, of 1795, of an Englishman, George Murray. By turning the flaps to either horizontal or vertical positions, 64 different letters and symbols (26) could be formed.

Visual Telegraph was affected by weather, and could not be used during the night. It was replaced by Electrical Telegraph in the mid of 19th century.

Foundation of Communication > Visual Telegraphy