Semaphore Telegraph (Edited from Wikipedia)

SUMMARY

A semaphore telegraph is a system of conveying information by means of visual , using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a fixed position.

The most widely used system was invented in 1792 in France by , and was popular in the late eighteenth to early nineteenth century. They were much faster than post riders for conveying a message over long distances, and also had cheaper long-term operating costs, once constructed.

Semaphore lines were a precursor of the , which would replace them half a century later, and would also be cheaper, faster, and more private. The distance that an can bridge is limited by geography and weather; thus, in practical use, most optical telegraphs used lines of relay stations to bridge longer distances. This also prevented the optical telegraph from crossing wide expanses of water, unless a convenient island could be used for a relay station.

HISTORY

Optical dates from ancient times, in the form of hydraulic telegraphs, torches and smoke signals. Modern design of semaphores was first foreseen by the British scientist Robert Hooke, who gave a vivid and comprehensive outline of visual telegraphy to the Royal Society in an 1684 submission in which he outlined many practical details. The system was never put into practice.

Sir Richard Lovell Edgeworth's proposed optical telegraph for use in Ireland. The rotational position of each one of the four indicators represented a number 1-7 (0 being "rest"), forming a four-digit number. The number stood for a particular word in a codebook.

Credit for the first successful optical telegraph goes to the French engineer Claude Chappe and his brothers in 1792, who succeeded in covering France with a network of

1 556 stations stretching a total distance of 4,800 kilometres (3,000 mi). Le système Chappe was used for military and national until the 1850s.

During 1790–1795, at the height of the French Revolution, France needed a swift and reliable system to thwart the war efforts of its enemies. France was surrounded by the forces of Britain, the Netherlands, Prussia, Austria, and Spain, the cities of Marseille and Lyon were in revolt, and the British Fleet held Toulon. The only advantage France held was the lack of cooperation between the allied forces due to their inadequate lines of communication.

In the summer of 1790, the Chappe brothers set about devising a system of communication that would allow the central government to receive intelligence and to transmit orders in the shortest possible time. On 2 March 1791 at 11am, they sent the message “If you succeed, you will soon bask in glory” between two cities separated by 10 miles. The first means used a combination of black and white panels, clocks, telescopes, and codebooks to send their message.

The Chappes carried out experiments during the next two years, and on two occasions their apparatus in Paris was destroyed by mobs who thought they were communicating with royalist forces. However, in the summer of 1792 Claude was charged with establishing a line of stations between Paris and Lille, a distance of about 143 miles. It was used to carry dispatches for the war between France and Austria.

The first symbol of a message to Lille would pass through 15 stations in only nine minutes. The speed of the line varied with the weather, but the line to Lille typically transferred 36 symbols, a complete message, in about 32 minutes. Another line of 50 stations was completed in 1798, covering 300 miles.

MEANING OF THE WORD

The word “semaphore” was coined in 1801 by the French inventor of the semaphore line itself, Claude Chappe. He composed it from the Greek words sêma , "sign"; and from phorós , "carrying.” Chappe also coined the word “telegraph.” The word semaphoric was first printed in English in 1808: "The newly constructed Semaphoric telegraphs", referring to the destruction of telegraphs in France.

The word semaphore was first printed in English in 1816: "The improved Semaphore has been erected on the top of the Admiralty", referring to the installation of a simpler telegraph. Semaphore telegraphs are also called "optical telegraphs", "shutter telegraph chains", "Chappe telegraphs" or "Napoleonic semaphore".

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