Optical telegraphs
Jan. 4th, 2025 10:02 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
glaurungI wrote this a while ago on Facebook and utterly forgot to crosspost it here.
American history classes usually peg the start of the telegraph to 1844, with Morse sending "what hath god wrought" from Washington to Baltimore. Actually a bunch of people in Europe and America had been mucking around with sending electrical signals over wires for three decades by that point: Morse's system was merely the first to have great success and go on to be used all over the world.
But the first long distance telegraph networks were not even electrical. Starting in the early 1790's, first France, then Sweden and England built extensive *optical* telegraph networks. Unlike the later electrical telegraphs, which were largely commercial operations from the get go, the early networks were entirely government funded and non-official communications were forbidden. By the early 1800's, countries all over Europe were using optical telegraph systems for sending long distance messages - this being the Napoleonic wars, the networks were mainly used for military dispatches. With Napoleon's defeat, some networks fell into disuse, but others switched to carrying shipping news and other government traffic.
Each network consisted of long series of towers, preferably on hills, with a direct line of sight from one to the next. The first tower would deploy its signals, and someone at the next tower, looking through a telescope, would see them and duplicate them on his own tower for the next tower in line to copy. Each country jingoistically implemented its own bespoke signalling system, even when that meant adopting a slower, harder to use method instead of some other nation's superior system. Nearly all of these networks were for government use only, and paid for out of military budgets.
The idea of an optical signalling system was old - Robert Hooke read a paper to the Royal Society suggesting a system in 1684, but no government saw the need for such a thing until the 1790's. After the revolution, France found itself at war with all its neighbours, and rapid communication became essential. Claude Chappe's semaphore system was just what the revolutionary government needed. It used two vanes on a movable arm. Varying the angles of the vanes and the arm itself allowed a lexicon of 194 signs. Later that was pared down to 94 semographic signs, which were used in pairs to create a code book of 8,000-ish words. During daylight, on days without fog or rain, messages could be sent from Paris to Lyon (500 kilometers away) in 9 minutes. The first line of towers was built in 1792, and within 4 decades France had a vast network of telegraph towers (that leads to a map on Wikipedia). Napoleon loved the system, and built signal lines in conquered territories as well as commissioning portable towers which he brought with him on campaign. Chappe called his invention the semaphore, but the name that stuck was télégraphe.
In Dumas's novel the Count of Monte Cristo, Dantes bribes an optical telegraph operator to transmit false information as part of his scheme to bankrupt his enemy Danglars. In real life, the first ever case of wire fraud occurred in France in 1834 when two bankers bribed telegraph operators to insert some stock market data into their official transmissions, disguised as coding mistakes. The telegraph was also used to prevent fraud, sending out news of the results of the French lottery, closing the gap between the drawing in Paris and the news reaching the provinces, during which fraudsters had long suckered people into buying worthless tickets.
Inspired by France's system, Sweden's Abraham Edelcrantz came up with a binary encoding system that was harder to see, but faster and simpler to operate than Chappe's semaphore signals. Each telegraph tower held a grid of 10 large black shutters which could be open (horizontal/invisible) or closed (vertical/visible). One offset shutter indicated an "A" prefix, and 3 groups of 3 indicated a 3 digit octal code, allowing a code book of 1024 words. By putting lights inside boxes with the shutters at either end, it was possible to transmit messages at night. A mechanical control panel enabled the operator to program the next code group in advance, then one press of a pedal moved all the shutters at once to display the next code group. Sweden's network was the largest after France's, but I haven't been able to find a map. :(
Sweden's network covered 200km in 1809. Most of it went into disuse with the end of the Napoleonic wars, but it was put back into service in the 1830's and continued to be expanded until 1854, when electrical telegraph systems began to take over. The country's fractured coastline and many islands made converting the optical network to an electrical one quite challenging, and Sweden's telecommunications system was a hybrid of optical and electrical from the 1850's through the 1870's. The last pair of optical stations were not shut down until 1881.
In England, George Murray devised a six shutter binary system. The first line was built in 1795, and the network encompassed sixty-five towers by 1808. As in Sweden, the system went into disuse after Napoleon's defeat, but in 1822 the Royal Navy rebuilt one line (from the Admiralty in London to Portsmouth), and after studying the matter, switched from binary shutters to a more easily seen system devised by Home Riggs Popham that, somewhat like the French system, used two semaphore signalling arms attached to a vertical pole. The line remained in service until it was replaced with an electrical telegraph in 1847.
Also in the 1820's, one of the few commercially owned and operated optical telegraph systems started up in the UK, with a line running from Holyhead in Wales to Liverpool, to enable news of incoming ships to reach the Liverpool stock market hours before the ships arrived in port.
Spain's first optical telegraph line went into service in 1800, and by the 1840's the country had three lines connecting Madrid to border and port cities - Barcelona, Cadiz, and Irun (the last is a town on the north coast at the border with France). Spain's very hilly landscape made running electrical lines difficult, and while the first electrical telegraph line began operating there in 1855, the last optical lines continued to be used until 1876.
Prussia came to the game very late, with a single Berlin-Koblenz line opening in 1833 and being replaced by an electrical system in 1849. Two other commercial lines carrying shipping news opened in Germany in 1837 and 1847: both shut down in the early 1850's. Prussia used a binary system like Sweden's, but with 12 shutters.
All of these systems paved the way for later electrical telegraph networks, as the operators of the time had to invent and implement data transmission protocols that are now taken for granted - things like error control, rate control, message priority, and so on.
The incredible speed with which the later electrical telegraph networks were built can at least partly be credited to the earlier optical networks making everyone aware of just how useful fast communication could be. Once a much faster, all-weather, and much more private and secure system came along, governments and industry were all on board despite the high up front costs.
Two last bits: Today's flag semaphore signals are adaptations of the those used by the British Admiralty in their 1830's optical telegraph. And, the many hills in England, Europe, and even parts of America which are today named the local equivalent of "telegraph hill," were all once places where an optical telegraph tower once stood.
American history classes usually peg the start of the telegraph to 1844, with Morse sending "what hath god wrought" from Washington to Baltimore. Actually a bunch of people in Europe and America had been mucking around with sending electrical signals over wires for three decades by that point: Morse's system was merely the first to have great success and go on to be used all over the world.
But the first long distance telegraph networks were not even electrical. Starting in the early 1790's, first France, then Sweden and England built extensive *optical* telegraph networks. Unlike the later electrical telegraphs, which were largely commercial operations from the get go, the early networks were entirely government funded and non-official communications were forbidden. By the early 1800's, countries all over Europe were using optical telegraph systems for sending long distance messages - this being the Napoleonic wars, the networks were mainly used for military dispatches. With Napoleon's defeat, some networks fell into disuse, but others switched to carrying shipping news and other government traffic.
Each network consisted of long series of towers, preferably on hills, with a direct line of sight from one to the next. The first tower would deploy its signals, and someone at the next tower, looking through a telescope, would see them and duplicate them on his own tower for the next tower in line to copy. Each country jingoistically implemented its own bespoke signalling system, even when that meant adopting a slower, harder to use method instead of some other nation's superior system. Nearly all of these networks were for government use only, and paid for out of military budgets.
The idea of an optical signalling system was old - Robert Hooke read a paper to the Royal Society suggesting a system in 1684, but no government saw the need for such a thing until the 1790's. After the revolution, France found itself at war with all its neighbours, and rapid communication became essential. Claude Chappe's semaphore system was just what the revolutionary government needed. It used two vanes on a movable arm. Varying the angles of the vanes and the arm itself allowed a lexicon of 194 signs. Later that was pared down to 94 semographic signs, which were used in pairs to create a code book of 8,000-ish words. During daylight, on days without fog or rain, messages could be sent from Paris to Lyon (500 kilometers away) in 9 minutes. The first line of towers was built in 1792, and within 4 decades France had a vast network of telegraph towers (that leads to a map on Wikipedia). Napoleon loved the system, and built signal lines in conquered territories as well as commissioning portable towers which he brought with him on campaign. Chappe called his invention the semaphore, but the name that stuck was télégraphe.
In Dumas's novel the Count of Monte Cristo, Dantes bribes an optical telegraph operator to transmit false information as part of his scheme to bankrupt his enemy Danglars. In real life, the first ever case of wire fraud occurred in France in 1834 when two bankers bribed telegraph operators to insert some stock market data into their official transmissions, disguised as coding mistakes. The telegraph was also used to prevent fraud, sending out news of the results of the French lottery, closing the gap between the drawing in Paris and the news reaching the provinces, during which fraudsters had long suckered people into buying worthless tickets.
Inspired by France's system, Sweden's Abraham Edelcrantz came up with a binary encoding system that was harder to see, but faster and simpler to operate than Chappe's semaphore signals. Each telegraph tower held a grid of 10 large black shutters which could be open (horizontal/invisible) or closed (vertical/visible). One offset shutter indicated an "A" prefix, and 3 groups of 3 indicated a 3 digit octal code, allowing a code book of 1024 words. By putting lights inside boxes with the shutters at either end, it was possible to transmit messages at night. A mechanical control panel enabled the operator to program the next code group in advance, then one press of a pedal moved all the shutters at once to display the next code group. Sweden's network was the largest after France's, but I haven't been able to find a map. :(
Sweden's network covered 200km in 1809. Most of it went into disuse with the end of the Napoleonic wars, but it was put back into service in the 1830's and continued to be expanded until 1854, when electrical telegraph systems began to take over. The country's fractured coastline and many islands made converting the optical network to an electrical one quite challenging, and Sweden's telecommunications system was a hybrid of optical and electrical from the 1850's through the 1870's. The last pair of optical stations were not shut down until 1881.
In England, George Murray devised a six shutter binary system. The first line was built in 1795, and the network encompassed sixty-five towers by 1808. As in Sweden, the system went into disuse after Napoleon's defeat, but in 1822 the Royal Navy rebuilt one line (from the Admiralty in London to Portsmouth), and after studying the matter, switched from binary shutters to a more easily seen system devised by Home Riggs Popham that, somewhat like the French system, used two semaphore signalling arms attached to a vertical pole. The line remained in service until it was replaced with an electrical telegraph in 1847.
Also in the 1820's, one of the few commercially owned and operated optical telegraph systems started up in the UK, with a line running from Holyhead in Wales to Liverpool, to enable news of incoming ships to reach the Liverpool stock market hours before the ships arrived in port.
Spain's first optical telegraph line went into service in 1800, and by the 1840's the country had three lines connecting Madrid to border and port cities - Barcelona, Cadiz, and Irun (the last is a town on the north coast at the border with France). Spain's very hilly landscape made running electrical lines difficult, and while the first electrical telegraph line began operating there in 1855, the last optical lines continued to be used until 1876.
Prussia came to the game very late, with a single Berlin-Koblenz line opening in 1833 and being replaced by an electrical system in 1849. Two other commercial lines carrying shipping news opened in Germany in 1837 and 1847: both shut down in the early 1850's. Prussia used a binary system like Sweden's, but with 12 shutters.
All of these systems paved the way for later electrical telegraph networks, as the operators of the time had to invent and implement data transmission protocols that are now taken for granted - things like error control, rate control, message priority, and so on.
The incredible speed with which the later electrical telegraph networks were built can at least partly be credited to the earlier optical networks making everyone aware of just how useful fast communication could be. Once a much faster, all-weather, and much more private and secure system came along, governments and industry were all on board despite the high up front costs.
Two last bits: Today's flag semaphore signals are adaptations of the those used by the British Admiralty in their 1830's optical telegraph. And, the many hills in England, Europe, and even parts of America which are today named the local equivalent of "telegraph hill," were all once places where an optical telegraph tower once stood.
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Date: 2025-01-04 04:53 pm (UTC)(no subject)
Date: 2025-05-15 11:20 pm (UTC)