Semaphore line

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This article is about the communication system using towers with pivoting shutters. For the now closed railway in Adelaide, Australia, see Semaphore railway line. For other uses, see Semaphore (disambiguation).


The system was invented in 1792 in France by Claude Chappe, and was popular in the late 18th to early 19th century.[1][2][3]


Modern derivatives of the semaphore system include flag semaphore (a flag relay system) and the heliograph (optical telegraphy using mirror-directed sunlight reflections).


The word semaphore was coined in 1801 by the French inventor of the Semaphore line, Claude Chappe, who also coined the word "telegraph".[4]

The word "semaphoric" was first printed in English in 1808: "The newly constructed Semaphoric telegraphs" referring to the destruction of telegraphs in France.[5] 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. The word was derived from "sémaphore", coined in French from Greek σῆμα (sêma, "sign") and φωρος (phoros, "bearer").[6]


Early designs[edit]



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.[7][8]

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.[9] 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 the high ground the signal would be observed from one station to the next by means of a telescope.[10] 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 256. He only returned to his idea in 1795, after hearing of Chappe's system.

Chappe system[edit]

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


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 “si vous réussissez, vous serez bientôt couverts de gloire” (If you succeed, you will soon bask in glory) between Brulon and Parce, a distance of 16 kilometres (9.9 mi). The first means used a combination of black and white panels, clocks, telescopes, and codebooks to send their message.


Diagram showing the Chappe system, as used simple for signalling letters and numbers (though it could also be used in an encoded form)

The Chappe brothers determined by experiment that it was easier to see the angle of a rod than to see the presence or absence of a panel. Their semaphore was composed of black movable wooden arms, the position of which indicated alphabetic letters. With counterweights (named forks) on the arms, the Chappe system was controlled by only two handles and was mechanically simple and reasonably robust. Each of the two 2-metre-long arms showed seven positions, and the 4.6-metre-long cross bar connecting the two arms had four different angles, for a total of 196 symbols (7x7x4). Night operation with lamps on the arms was unsuccessful.

To speed up transmission and to provide some semblance of security a code book was developed for use with semaphore lines. The Chappes' corporation used a code that took 92 of the basic symbols two at a time to yield 8,464 coded words and phrases.



Use in various countries[edit]


The Chappe Network in France

After Chappe's initial line, the Paris to Strasbourg with 50 stations followed soon after. By 1824, the Chappe brothers were promoting the semaphore lines for commercial use, especially to transmit the costs of commodities. Napoleon Bonaparte saw the military advantage in being able to transmit information between locations, and carried a portable semaphore with his headquarters. This allowed him to coordinate forces and logistics over longer distances than any other army of his time. However because stations had to be within sight of each other, and because the efficient operation of the network required well trained and disciplined operators, the costs of administration and wages were a continuous source of financial difficulties. Only when the system was funded by the proceeds of its own lottery did costs come under control.

A Chappe semaphore tower near Saverne, France




At the same time as Chappe, the Swedish inventor Abraham Niclas Edelcrantz experimented with the optical telegraph in Sweden. In 1794 he inaugurated his telegraph with a poem dedicated to the Swedish King on his birthday. The message went from the Palace in Stockholm to the King at Drottningholm.



United Kingdom[edit]


In Ireland, Richard Lovell Edgeworth returned to his earlier work in 1794, and proposed a telegraph there to warn against an anticipated French invasion; however, the proposal was not implemented. Lord George Murray, stimulated by reports of the Chappe semaphore, proposed a system of visual telegraphy to the British Admiralty in 1795.[3] He employed rectangular framework towers with six, five feet high octagonal shutters on horizontal axes that flipped between horizontal and vertical positions to signal. [12] The Rev. Mr Gamble also proposed two distinct five element systems in 1795: one using five shutters, and one using five ten foot poles.[3] The British Admiralty accepted Murray's system in September 1795, and the first system was the 15 site chain from London to Deal.[13] Messages passed from London to Deal in about sixty seconds, and sixty-five sites were in use by 1808.[13]


Chains of Murray's shutter telegraph stations were built along the following routes: LondonDeal and Sheerness, London—Great Yarmouth and London—Portsmouth and Plymouth. The shutter stations were temporary wooden huts, and at the conclusion of the Napoleonic wars they were no longer necessary, and were closed down by the Admiralty in March 1816.[14]


Subsequently the Admiralty decided to establish a permanent link to Portsmouth and built a chain of semaphore stations. Work started in December 1820[14] and the line was operational from 1822 until 1847, when the railway and electric telegraph provided a better means of communication. The semaphore line did not use the same locations as the shutter chain, but followed almost the same route with 15 stations -


The Board of Port of Liverpool obtained a Private Act of Parliament to construct a chain of Popham optical semaphore stations from LiverpoolHolyhead in 1825.[15]

A semaphore-based successor for the London to Plymouth shutter telegraph chain, branching much closer to London, at Chatley Heath in Surrey, was started but abandoned before completion.

Many of the prominences on which the towers were built (telegraph hills) are known as 'Telegraph Hill' to this day. As in France the network required lavish amounts of money and manpower to operate and could only be justified as a defence need.

Other countries[edit]

Optical telegraph in the harbour of Bremerhaven, Germany.





The Kingdom of Prussia began with a line 750 kilometres (470 mi) long between Berlin and Coblenz in 1833, and in Russia, Tsar Nicolas I inaugurated a line between Moscow and Warsaw of 1,200 kilometres (750 mi) length in 1833; it needed 220 stations manned by 1,320 operators.

In the United States the first optical telegraph was built by Jonathan Grout. It was a 104 kilometres (65 mi) line connecting Martha's Vineyard with Boston, and its purpose was to transmit news about shipping. One of the principal hills in San Francisco, California is also named "Telegraph Hill", after the semaphore telegraph which was established there in 1849 to signal the arrival of ships into San Francisco Bay.

The semaphores were successful enough that Samuel Morse failed to sell the electrical telegraph to the French government. However, France finally committed to replace semaphores with electric telegraphs in 1846. Electric telegraphs are both more private and almost completely unaffected by weather; they also work at night. Many contemporaries predicted the failure of electric telegraphs because "they are so easy to cut."[19] The last stationary semaphore link in regular service was in Sweden, connecting an island with a mainland telegraph line. It went out of service in 1880.

In popular culture[edit]


The Chappe telegraph appeared in contemporary fiction and comic strips. In "Mister Pencil" (1831), comic strip by Rodolphe Töpffer, a dog fallen on a Chappe telegraph's arm and its master attempting to help provoke an international crisis by involuntarily transmitting disturbing messages. In "Lucien Leuwen" (1834), Stendhal pictures a power struggle between Lucien Leuwen and the prefect M. de Séranville with the telegraph's director M. Lamorte. In Chapter 60 ("The Telegraph") of Alexandre Dumas' The Count of Monte Cristo (1844), the title character describes with fascination the semaphore line's moving arms. "I had at times seen rise at the end of a road, on a hillock and in the bright light of the sun, these black folding arms looking like the legs of an immense beetle."[20] He later bribes a semaphore operator to relay a false message in order to manipulate the French financial market. Dumas also describes in details the functioning of a Chappe telegraph line. In the Hector Malot's novel Romain Kalbris (1869), one of the characters—a girl named Dielette, describes her home in Paris as " to a church near which there was a clock tower. On top of the tower there were two large black arms, moving all day this way and that. [I was told later] that this was Saint-Eustache church and that these large black arms were a telegraph."[21]

The system was referenced in later works such as C. S. Forester's Hornblower and the Hotspur (1962), where the destruction of a French semaphore tower and a shore battery is a key plot point. A similar event is also the focus of the seventh episode of the television series. In the young adult fiction book Death Cloud by Andy Lane (2010), Mycroft Holmes tells 14-year-old Sherlock Holmes about semaphore stations, commenting about his school beforehand, saying "All the Latin a boy can cram into his skull, but nothing of practical use."

Fictional versions of the telegraph appear in literature. In the alternative history novel, Lest Darkness Fall (1939), by L. Sprague de Camp, the protagonist, a 20th Century man who falls into Dark Age Rome, develops a semaphore system to warn of invasion. To make it practical he also invents the telescope. Pavane (1968), an alternate history novel by Keith Roberts, features a society where long distance communication is by a network of semaphores operated by the powerful Guild of Signallers, and Terry Pratchett's Discworld novels (1983) describe a system of 8-shutter semaphore towers, known as Clacks which occupy a similar role to that of the Internet. Using advanced clacks coding it is possible not only to send very fast telegrams, but also to encode pictures and send them long-distance, and shopping and banking via the clacks is also mentioned. In David Weber's Safehold series (2007), a world-wide Semaphore system is used by the Church to help them maintain their dominion over the world. In Alastair Reynolds' Terminal World (2010), the distant-future terrain is criss-crossed with semaphore lines relaying information between the one remaining city, Spearpoint, outlying communities and the airborne community Swarm.

See also[edit]


  2. ^ a b c Telegraph Vol 10, Encyclopaedia Britannica, 6th Edition, 1824 pp. 645–651
  5. ^ 500 Years of New Words, Bill Sherk
  6. ^ Oxford English Dictionary
  8. ^ "History of the Telephone part2". Retrieved 2013-06-17. 
  9. ^ Rees, Abraham, ed. (1802–1820). "Telegraph". Cyclopædia 35. London: Longman, Hurst, Rees, Orme & Brown. Unpaginated work: pages 9-11 of the article entry. 
  14. ^ a b c Military Signals from the South Coast, John Goodwin, 2000
  19. ^ Holzmann, Gerard. "Data Communications: The First 2,500 Years". Retrieved 28 June 2011. 
  20. ^ Page 84 in
  21. ^ See second paragraph in

Further reading[edit]


External links[edit]