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Optical Telegraphs

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Since the late 1500s, Europe had been a breeding ground for fantastical rumours of the existence of a magical communication machine. Such an invention, whereby messages could be sent instantly over long distances, was but a dream in those days. Until a generation of amateur inventors developed several methods of sending instant messages, no one could produce evidence that such a communications device was possible.

Claude Chappe was among these pioneers. When his ecclesiastical ambition became a casualty of the French Revolution in 1789, Chappe turned his attention to the sciences, and began tinkering with the idea of an electric messaging system. He and his four brothers, Ignace, Pierre, René, and Abraham set up a shop in Brûlon, France to continue work on telegraph technology. When their initial endeavours failed—the electric telegraph being still decades away—Chappe turned his attention instead to simpler methods of distance communication.

The earliest of these experiments relied on the transmission of sound through striking a metal dish. However, Chappe reasoned that sight messages could be sent much further and more quickly.

Before this breakthrough, the world had relied upon messengers, even as it had for thousands of years. Beyond this, developments were of a low-tech variety, limited to communicating through visual means using flags and smoke signals.

Chappe merely enhanced these visual methods by creating his first optical telegraph. His "far writer" consisted of a long pivoting board, which was painted black on one side and white on the other. By using synchronized clocks and a simple telescope, Chappe and his brother René exchanged messages by flipping the board from black to white and back again at set times in accordance with the letters they wished to convey.

In 1791, he enlisted his brothers René and Pierre to help him conduct experiments using several varieties of the tachygraphe that he had invented. These early versions of an optical telegraph were tested by sending messages between Brûlon and the town of Parsé—about 16 kilometres away. On 2 March of that year, he demonstrated the invention in the presence of local officials, and while initially it was met with great enthusiasm, that quickly waned in the face of the Napoleonic Wars. His second official demonstration, in Belleville in 1792, ended in disaster when a mob attacked him on the belief that he was sending coded messages to the Royalists.

Chappe had better luck with his second optical telegraph—or semaphore—system, which consisted of two black wooden arms joined by a crossbar and mounted atop a tower. By using a pair of ropes and a system of pulleys and levers, each counterweighted arm was capable of seven different positions, whereas the crossbar could move into four different positions, for a total of 196 different positions in combination.

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