Optical telegraph

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[edit] Development

Claude Chappe is credited with creating the first practical means of sending information over great distances. On March 2, 1791 at 11 A.M., Chappe and his brother sent the message “si vous reussissez, vous serez bientot couvert de glorie” (If you succeed, you will soon bask in glory) between Brulon and Parce, a distance of ten miles. The first means used a combination of black and white panels, clocks, telescopes, and codebooks to send their message.

Later, Chappe designed a system that consisted of two rotating arms on the end of a longer rotating bar. The bar, also known as the regulator, could be alligned horizontally or vertically. Each arm, or indicator, could be rotated to one of seven positions in forty-five degreen increments. The arms were from three to thirty feet long, black, and counterweighted, moved by only two handles. Lamps mounted on the arms proved unsatisfactory for night use. The relay towers were placed from 12 to 25 km (10 to 20 miles) apart. Each tower had a telescope pointing both up and down the relay line.

[edit] Implementation

Claude's brother, Ignace Chappe (1760-1829) was a member of the Legislative Assembly during the French Revolution. With his help, the Assembly supported a proposal to build a relay line from Paris to Lille (fifteen stations, about 120 miles), to carry dispatches from the war.

In 1792, the first messages were successfully sent between Paris and Lille. In 1794 the semaphore line informed Parisians of the capture of Condé-sur-l'Escaut from the Austrians less than an hour after it occurred. Other lines were built, including a line from Paris to Toulon. The system was widely copied by other European states, and was used by Napoleon to coordinate his empire and army.