বাঁকুড়ার জয়পুর জঙ্গলে ইংরেজ আমলের টেলিগ্রাম টাওয়ার খুঁজে পেলাম | simafore tower

A semaphore telegraph is a system of conveying information by means of visual signals, 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 Claude Chappe, and was popular in the late eighteenth to early nineteenth century.[1][2][3] They were much faster thanpost 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 electrical telegraph, which would replace them half a century later, and would also be cheaper, faster, and more private. The distance that an optical telegraph can bridge is limited bygeography 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. Modern derivatives of the semaphore system include flag semaphore (a flag relay system) and the heliograph (optical telegraphy using mirror-directed sunlight reflections).

Etymology and terminology

The word semaphore was coined in 1801 by the French inventor of the semaphore line itself, Claude Chappe.[4] He composed it from the Greek elements σῆμα (sêma, "sign"); and from φορός (phorós, "carrying"),[5] or φορά (phorá, "a carrying") from φέρειν (phérein, "to bear").[6] 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.[7] 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 invented by Sir Home Popham.[citation needed]Semaphore telegraphs are also called "optical telegraphs", "shutter telegraph chains", "Chappe telegraphs" or "Napoleonic semaphore".

History

Early designs
Illustration showing Robert Hooke's proposed system. At top are various symbols that might be used; ABCE indicates the frame, and D the screen behind which each of the symbols are hidden when not in use.

Optical telegraphy dates from ancient times, in the form of hydraulic telegraphs, torches (as used by ancient cultures since the discovery of fire) andsmoke signals. Modern design of semaphores was first foreseen by the British polymath 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 (which was motivated by military concerns, following the recent Battle of Vienna in 1683) 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 indicaters represented a number 1-7 (0 being "rest"), forming a four-digit number. The number stood for a particular word in a codebook.

One of the first experiments of optical signalling was carried out by the Anglo-Irish landowner and inventor, Sir Richard Lovell Edgeworth in 1767.[10] He placed a bet with his friend, the horse racing gambler Lord Marsh, that he could transmit knowledge of the outcome of the race in just one hour. Using a network of signalling sections erected on high ground, the signal would be observed from one station to the next by means of a telescope.The signal itself consisted of a large pointer that could be placed into eight possible positions in 45 degree increments. A series of two such signals gave a total 64 code elements and a third signal took it up to 512. He only returned to his idea in 1795, after hearing of Chappe's system.

Chappe system
Demonstration of the semaphore

Credit for the first successful optical telegraph goes to the French engineer Claude Chappe and his brothers in 1792, who succeeded in covering Francewith a network of 556 stations stretching a total distance of 4,800 kilometres (3,000 mi). Le système Chappe was used for military and national communications until the 1850s.

Development

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