Editing Optical telegraph (section)

===France===
[[File:Chappe semaphore.jpg|thumb|upright|19th-century 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 {{convert|4,800|km}}. ''Le système Chappe'' was used for military and national communications until the 1850s.<!-- Another source says 534 stations and more than 5,000km. https://www.bbc.co.uk/news/magazine-22909590 -->

====Development in France<!-- "France" required to avoid repeated heandin name per [[MOS:HEAD]] -->====
During 1790–1795, at the height of the [[French Revolution]], France needed a swift and reliable [[military communications]] 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 [[History of the Royal Navy#Wars with France, 1690–1815|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 mid-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. Chappe considered many possible methods including audio and smoke. He even considered using electricity, but could not find insulation for the conductors that would withstand the high-voltage [[electrostatic generator|electrostatic sources]] available at the time.<ref>Patrice Flichy, ''Dynamics of Modern Communication'', p. 33, SAGE, 1995 {{ISBN|144622712X}}</ref><ref>Holzmann & Pehrson, p. 53</ref>

Chappe settled on an optical system and the first public demonstration occurred on 2 March 1791 between [[Brûlon]] and [[Parcé-sur-Sarthe|Parcé]], a distance of {{convert|16|km}}. The system consisted of a modified pendulum clock at each end with dials marked with ten numerals. The hands of the clocks almost certainly moved much faster than a normal clock. The hands of both clocks were set in motion at the same time with a synchronisation signal. Further signals indicated the time at which the dial should be read. The numbers sent were then looked up in a [[codebook]]. In their preliminary experiments over a shorter distance, the Chappes had banged a pan for synchronisation. In the demonstration, they used black and white panels observed with a telescope. The message to be sent was chosen by town officials at Brûlon and sent by René Chappe to Claude Chappe at Parcé who had no pre-knowledge of the message. The message read "si vous réussissez, vous serez bientôt couverts de gloire" (If you succeed, you will soon bask in glory). It was only later that Chappe realised that he could dispense with the clocks and the synchronisation system itself could be used to pass messages.<ref>Holzmann & Pehrson, pp. 53–55</ref>

The Chappes carried out experiments during the next two years, and on two occasions their apparatus at [[Place de l'Étoile]], [[Paris]] was destroyed by mobs who thought they were communicating with [[Chouannerie|royalist]] forces. Their cause was assisted by Ignace Chappe being elected to the [[National Legislative Assembly (France)|Legislative Assembly]]. In the summer of 1792 Claude was appointed ''Ingénieur-Télégraphiste'' and charged with establishing a line of stations between Paris and [[Lille]], a distance of 230 kilometres (about 143 miles). It was used to carry dispatches for the war between France and Austria. In 1794, it brought news of a French capture of [[Condé-sur-l'Escaut]] from the Austrians less than an hour after it occurred.<ref>[https://www.bbc.co.uk/news/magazine-22909590 How Napoleon's semaphore telegraph changed the world], BBC News, Hugh Schofield, 16 June 2013</ref><!-- Note: this BBC source tells this story well, and supports the Lille and Conde statements, but was not used for the whole section, which remains 'unreferenced' --> 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 488&nbsp;km between Paris and [[Strasbourg]].<ref>{{Cite web|url=https://ethw.org/w/images/1/17/Dilhac.pdf|title = Engineering and Technology History Wiki}}</ref> From 1803 on, the French also used the 3-arm Depillon semaphore at coastal locations to provide warning of British incursions.<ref name="Burns2004"/>

English military engineer [[Sir William Congreve, 1st Baronet|William Congreve]] observed that at the [[Battle of Menin (1793)|Battle of Vervik]] of 1793 French commanders directed their forces by using the sails of a prominent local windmill as an improvised signal station. Two of the four sails of the mill had been removed to resemble the arm of the new telegraph.<ref>{{cite book |last1=Gamble |first1=John |author1-link=John Gamble (priest) |title=An essay on the different modes of communication by signals |date=1797 |publisher=[[William Miller (British publisher)|William Miller]] |location=London |oclc=495253065 |page=66}}</ref><ref>{{cite journal |last1=ffoulkes |first1=Charles |author1-link=Charles ffoulkes |title=Notes on the Development of Signals Used for Military Purposes |journal=Journal of the Society for Army Historical Research |date=1943 |volume=22 |issue=85 |pages=20–27 |jstor=44219957 |url=https://www.jstor.org/stable/44219957 |issn=0037-9700}}</ref>

====Chappe system technical operation====
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 two black movable wooden arms, connected by a cross bar; the positions of all three of these components together indicated an alphabetic letter. 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 could display seven positions, and the 4.6-metre-long cross bar connecting the two arms could display four different angles, for a total of 196 symbols (7×7×4). Night operation with lamps on the arms was unsuccessful.<ref>Holzmann & Pehrson, p. 213</ref> 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.

The revised Chappe system of 1795 provided not only a set of codes but also an operational protocol intended to maximize line [[throughput]]. Symbols were transmitted in cycles of "2 steps and 3 movements."

*'''Step 1, movement 1 (setup)''': The operator turned the indicator arms to align with the cross bar, forming a non-symbol, and then turned the cross bar into position for the next symbol.
*'''Step 1, movement 2 (transmission)''': The operator positioned the indicator arms for current symbol and waited for the downline station to copy it.
*'''Step 2, movement 3 (completion)''': The operator turned the cross bar to a vertical or horizontal position, indicating the end of a cycle.

In this manner, each symbol could propagate down the line as quickly as operators could successfully copy it, with [[Acknowledgement (data networks)|acknowledgement]] and [[Flow control (data)|flow control]] built into the protocol. A symbol sent from Paris took 2 minutes to reach Lille through 22 stations and 9 minutes to reach Lyon through 50 stations. A rate of 2–3 symbols per minute was typical, with the higher figure being prone to errors. This corresponds to only 0.4–0.6 [[wpm]], but with messages limited to those contained in the code book, this could be dramatically increased.<ref>Holzmann & Pehrson</ref><ref>{{cite web |url=http://chappe.ec-lyon.fr/message.html |title=Les dépêches |website=chappe.ec-lyon.fr |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20140202183712/http://chappe.ec-lyon.fr/message.html |archive-date=2 February 2014 |url-status=dead}}</ref> An additional benefit is that, if the code is kept secret, the content of transmitted messages can be concealed from both onlookers and system operators, even if they are aware that a message is being transmitted. This has remained an important feature of encrypted communications even as the technology for transmitting data has evolved.<ref>{{Cite news |date=2013-06-16 |title=How Napoleon's semaphore telegraph changed the world |url=https://www.bbc.com/news/magazine-22909590 |access-date=2024-11-08 |work=BBC News |language=en-GB}}</ref>

====History in France====
[[File:Reseau chappe77.png|thumb|right|The Chappe Network in France]]
After Chappe's initial line (between Paris and Lille), the Paris to [[Strasbourg]] with 50 stations followed soon after (1798). [[Napoleon Bonaparte]] made full use of the telegraph by obtaining speedy information on enemy movements. In 1801 he had Abraham Chappe build an extra-large station to transmit across the English Channel in preparation for an invasion of Britain. A pair of such stations were built on a test line over a comparable distance. The line to [[Calais]] was extended to [[Boulogne]] in anticipation and a new design station was briefly in operation at Boulogne, but the invasion never happened. In 1812, Napoleon took up another design of Abraham Chappe for a mobile telegraph that could be taken with him on campaign. This was still in use in 1853 during the [[Crimean War]].<ref>Holzmann & Pehrson, pp. 71–73</ref>

The invention of the telegraph was followed by an enthusiasm concerning its potential to support [[direct democracy]]. For instance, based on [[Jean-Jacques Rousseau|Rousseau]]'s argument that direct democracy was improbable in large constituencies, the French Intellectual [[Alexandre-Théophile Vandermonde]] commented:

{{Blockquote|Something has been said about the telegraph which appears perfectly right to me and gives the right measure of its importance. Such invention might be enough to render democracy possible in its largest scale. Many respectable men, among them Jean-Jacques Rousseau, have thought that democracy was impossible within large constituencies.… The invention of the telegraph is a novelty that Rousseau did not expect to happen. It enables long-distance communication at the same pace and clarity than that of conversation in a living room. This solution may address by itself the objections to large [direct] democratic republics. It may even be done in the absence of representative constitutions.<ref>{{Cite journal|last=Mattelart|first=Armand|date=1999|title=La communication et la promesse de rédemption|url=https://www.persee.fr/doc/quad_0987-1381_1999_num_40_1_1428|journal=Quaderni|volume=40|issue=1|pages=69–78|doi=10.3406/quad.1999.1428}}</ref>}}

The operational costs of the telegraph in the year 1799/1800 were 434,000 [[franc]]s ($1.2 million in 2015 in silver costs<ref name=Edvinsson>Rodney Edvinsson, [https://www.historicalstatistics.org/Currencyconverter.html Historical Currency Converter, accessed 8 January 2021.]</ref>). In December 1800, Napoleon cut the budget of the telegraph system by 150,000 francs ($400,000 in 2015)<ref name=Edvinsson/> leading to the Paris-Lyons line being temporarily closed. Chappe sought commercial uses of the system to make up the deficit, including use by industry, the financial sector, and newspapers. Only one proposal was immediately approved—the transmission of results from the state-run lottery. No non-government uses were approved. The lottery had been abused for years by fraudsters who knew the results, selling tickets in provincial towns after the announcement in Paris, but before the news had reached those towns.<ref>{{multiref|Shelby T. McCloy, ''French Inventions of the Eighteenth Century'', p. 46, University Press of Kentucky, 2015 {{isbn|0813163978}}.|Rollo Appleyard, ''Pioneers of Electrical Communication'', pp. 271–272, Books for Libraries Press, 1968 (reprint of Macmillan, 1930) {{oclc|682063110}}.}}</ref>

[[File:Tour du telegraphe Chappe Saverne 02.JPG|thumb|left|A Chappe semaphore tower near [[Saverne]], France]]
In 1819 [[Norwich Duff]], a young British Naval officer, visiting [[Clermont-en-Argonne]], walked up to the telegraph station there and engaged the signalman in conversation. Here is his note of the man's information:<ref>{{usurped|1=[https://web.archive.org/web/20070624023608/http://www.kittybrewster.com/images/Norwich_Duff_Journal_Intro.htm Commander Norwich Duff's European Tour Journal, 1819]}}, www.kittybrewster.com, archived 24 June 2007.</ref>

{{Blockquote|The pay is twenty five ''[[Solidus (coin)#France|sous]]'' per day and he [the signalman] is obliged to be there from day light till dark, at present from half past three till half past eight; there are only two of them and for every minute a signal is left without being answered they pay five ''sous'': this is a part of the branch which communicates with Strasburg and a message arrives there from Paris in six minutes it is here in four.<ref>{{usurped|1=[https://web.archive.org/web/20050123042146/http://www.kittybrewster.com/images/Norwich_Duff_Journal_pages022.htm Journal of Norwich Duff]}}, 13 July 1819.</ref>|Norwich Duff}}

The network was reserved for government use, but an early case of [[wire fraud]] occurred in 1834 when two bankers, François and Joseph Blanc, bribed the operators at a station near [[Tours]] on the line between Paris and [[Bordeaux]] to pass Paris stock exchange information to an accomplice in Bordeaux. It took three days for the information to travel the 300 mile distance, giving the schemers plenty of time to play the market. An accomplice at Paris would know whether the market was going up or down days before the information arrived in Bordeaux via the newspapers, after which Bordeaux was sure to follow. The message could not be inserted in the telegraph directly because it would have been detected. Instead, pre-arranged deliberate errors were introduced into existing messages which were visible to an observer at Bordeaux. Tours was chosen because it was a division station where messages were purged of errors by an inspector who was privy to the secret code used and unknown to the ordinary operators. The scheme would not work if the errors were inserted prior to Tours. The operators were told whether the market was going up or down by the colour of packages (either white or grey paper wrapping) sent by [[mail coach]], or, according to another anecdote, if the wife of the Tours operator received a package of socks (down) or gloves (up) thus avoiding any evidence of misdeed being put in writing.<ref>{{cite book |last= Berloquin|first= Pierre|date= 2008|title= Hidden Codes & Grand Designs|publisher= Sterling|page= 25|isbn=978-1-4027-7300-6}}</ref> The scheme operated for two years until it was discovered in 1836.<ref>Holzmann & Pehrson, pp. 75–76</ref><ref>{{cite web|last1=Holzmann |first1=Gerard J. |url=https://www.inc.com/magazine/19990915/13554.html |title=Taking stock |publisher=Inc |date=15 September 1999}}</ref>

The French optical system remained in use for many years after other countries had switched to the [[electrical telegraph]]. Partly, this was due to inertia; France had the most extensive optical system and hence the most difficult to replace. But there were also arguments put forward for the superiority of the optical system. One of these was that the optical system is not so vulnerable to saboteurs as an electrical system with many miles of unguarded wire. [[Samuel Morse]] failed to sell the electrical telegraph to the French government. Eventually the advantages of the electrical telegraph of improved privacy, and all-weather and nighttime operation won out.<ref>{{cite web|last=Holzmann|first=Gerard|title=Data Communications: The First 2,500 Years|url=http://spinroot.com/gerard/pdf/hamburg94b.pdf|access-date=28 June 2011}}</ref> A decision was made in 1846 to replace the optical telegraph with the [[Foy–Breguet telegraph|Foy–Breguet electrical telegraph]] after a successful trial on the [[Rouen]] line. This system had a display which mimicked the look of the Chappe telegraph indicators to make it familiar to telegraph operators. [[Jules Guyot]] issued a dire warning of the consequences of what he considered to be a serious mistake. It took almost a decade before the optical telegraph was completely decommissioned. One of the last messages sent over the French semaphore was the report of the [[Siege of Sevastopol (1854–1855)|fall of Sebastopol]] in 1855.<ref>Holzmann & Pehrson, pp. 92–94</ref>