The term optical telegraphy is generally understood to mean telegraphy over long distances using optical or a combination of optical and acoustic devices. Means for this are z. B. simple flashing mirrors (see indicators ) and more complex levels telegraph ( heliograph ), Morse lamps , Winkzeichen ( "WigWag" or nautical) and flag signals .
With optical telegraph that of is specifically Claude Chappe installed in the late 18th century in France System optical-mechanical telegraph lines indicated that until the advent of the electric telegraph across the middle of the 19th century also in the whole of Europe was used.
Smoke and fire signals were used to convey messages even in ancient times . The Greek poet Aeschylus described in his drama Agamemnon how the news of the Greek victory over Troy in 1184 BC. BC reached with a fire string from Troy to Argos , 555 km away . The historian Thucydides reported the use of fire signals in the Peloponnesian War (431–404 BC). The Romans set up watchtowers along the borders of the Imperium Romanum , which communicated with each other via fire signals, as in Germania along the Limes from the Rhine to the Danube .
However, this simple optical telegraph could only transmit previously agreed messages. The Greek historian Polybios first described the idea of conveying freely formulable messages with the help of fire sign telegraphy: Behind a large sign stood two "telegraph operators" who positioned torches at a certain position to the left or right of the sign according to the letters to be sent.
Optical telegraphs of the modern age
The starting point for modern optical telegraphy was the development of the telescope in 1608 by Dutch eyeglass makers, with which the range of human vision increased considerably. As early as 1684, Robert Hooke presented his idea to the Royal Society in London for the transmission of "Thoughts over great distances", the technical implementation of which, however, proved to be problematic. Large boards described with letters should be set up on a mast system with the help of cables and read with the help of a telescope.
Little is known about the first attempts by Christoph Ludwig Hoffmann . In a letter to Count Ludwig, son of Count Karl von Bentheim Steinfurt, it says:
“During his reign I invented telegraphy in Burgsteinfurt. In Munster I had an abbreviated message printed about this matter in 1782, ten years earlier than the French made something known to the world. "
In an article entitled Description d'un télégraphe très simple et à la portée de tout le monde. A Paris et Amsterdam, 1800 one finds the following note (translated here): "During the Seven Years' War it was carried out in Schönbusch on the hill near Burghorst (Borghorst)." These experiments were not continued and were forgotten.
Only the French technician Claude Chappe succeeded at the time of the French Revolution with a technically practicable, optical telegraphy device, based on the transmission of characters with the help of swiveling signal arms (also wing telegraph or semaphore ). On a high mast there were two swiveling crossbars with two further swiveling bars at each end, so that, depending on the position, different letters could be signaled using a code.
Building on the ideas of the physicist Guillaume Amontons , who carried out the first experiments on signal transmission as early as 1690, Chappe was able to convince the legislative national assembly in 1792 to set up a 70 km test route between Ménilmontant (now a Parisian quarter), Écouen and Saint-Martin-du-Tertre convince. The year before, he had successfully demonstrated the semaphore to the public with his brothers in Parcé-sur-Sarthe and Brûlon .
Several series of tests showed that the system was easy to use and robust. In 1794, for example, the first regular telegraph line between Paris and Lille could be set up, bridging 270 km with 22 semaphore stations. The time it took to transfer a single letter was an impressive two minutes at the time. Above all, the flexibility and speed convinced the military of the rapid establishment of a nationwide optical-mechanical telegraph network.
When transmitting messages, the crossbar had to be horizontal, vertical or diagonal. The signal arms could each protrude at an angle of 45 °, 90 °, 135 °, 225 °, 270 ° and 315 ° or be folded back onto the crossbar. In total, this resulted in 7 * 7 * 4 = 196 signals. Of these, 104 were used for transmission control and 92 for message transmission. A code word consisted of two consecutive signals, so that 92 * 92 = 8464 code words were available.
The telegraph stations were between nine and twelve kilometers apart, depending on the nature of the terrain and the visibility, so that the signs of the neighboring station could still be seen with a telescope. Two “telegraph operators” worked in each station, reading the characters from one of the two neighboring stations, setting them up at their station themselves and thereby passing them on to the neighboring station.
Napoléon Bonaparte made use of the system, and it enabled him to communicate better between the various units than any other army of the time. The disadvantage that the signal masts could be seen by everyone and the military messages could therefore also be read by unauthorized persons was overcome by the introduction of secret codes .
By 1845, a nationwide telegraph network originating from Paris had been established in France, connecting the capital with all the major cities in the country. However, optical telegraphy always had to contend with weather-related communication problems. Storms, poor visibility or the onset of twilight caused irregular and unreliable operation. The attempt to attach lamps to the signal arms did not prove successful.
The system was adopted in many other European countries and, due to the military importance of fast communication, was mainly operated by the states. Lines were also implemented in the USA, for example from New York to Philadelphia, albeit on a modest scale. Under Muhammad Ali Pasha , an opto-mechanical telegraph was also set up between Alexandria, Cairo and Suez in Egypt.
Prussian optical telegraphy
The first optical telegraph line on what is now German territory was the French optical telegraph line Metz – Mainz from 1813. The next was not added until 1830 between Berlin and Potsdam . However, this was soon no longer enough. Since Prussia had received the Rhineland and was supposed to guard the border with France, a stationary system on a large scale was required for rapid communication.
This was under the direction of the major in the General Staff Franz August O'Etzel (1783-1850) and the developer of the telegraph, the Privy Postal Councilor Carl Philipp Heinrich Pistor (1778-1847), who was also responsible for equipping the stations with signal transmitters and telescopes , created.
The Prussian optical telegraph led from the observatory in Dorotheenstrasse in Berlin via the Dahlem village church to Telegrafenberg near Potsdam, on via Magdeburg , Oschersleben, Veltheim, Liebenburg, then between Hahausen near Seesen and Bevern near Holzminden through Brunswick to the Köterberg west of the Weser to Prussian Westphalia via Paderborn to Cologne and from there to Koblenz . Between 1832 and 1852 this line existed for a length of almost 550 km. A reconstructed station of this telegraph line can be viewed in Cologne- Flittard , complete with a reconstructed pointer device on the roof. The stations Neuwegersleben near Oschersleben and Oeynhausen near Nieheim / Westf. and the Straßenhauser station in the Neuwied district were also reconstructed and set up as a museum. The tower of station 28 on the Burgberg near Bevern (Holzminden district) is still standing.
Due to military secrecy, only a few code books have survived . The Prussian bar telegraph followed roughly the system of the Englishman Barnard L. Watson. At the top of a mast boom six wings were mounted, which were connected to an observation room by cords running over pulleys and could be swiveled from there. With a total of 4096 wing positions, a complex transmission system was thus possible. The messages were observed and passed on from station to station and were many times faster than messengers on horseback, on which one had previously been dependent.
Optical telegraphy in Northern Germany
The Hamburg optical telegraph between Hamburg and Cuxhaven was opened on March 18, 1838 . In 1836, Johann Ludwig Schmidt received a concession from the Senate of the Free and Hanseatic City of Hamburg to operate this line. In 1847 the connection to Bremerhaven and Bremen was added. Around 1850 the optical telegraph gradually ceased its service because it was economically inferior to the Bremen – Bremerhaven electrical telegraph line, which was also opened in 1847 . Noteworthy is Friedrich Clemens Gerke , who worked in both companies and played a prominent role, especially later on when the electric telegraph was introduced on the same route.
The optical telegraph in Hamburg and Bremen was the first German publicly accessible communication medium of its kind, founded and used by merchants. In contrast, the Prussian system (like the French system at first) served only the administration and the military.
Optical telegraphy in southern Germany
At the beginning of October 1808 one of the first telegraphic posts was set up in Augsburg : signs in white, blue and red flags were given from the tower of the Ulrichskirche . At the beginning of the 19th century there were systems for a few years, for example on the Ammersee from Dießen to Andechs and Seefeld by the dean P. Michael Rummelsberger.
Structural remains and replicas of the optical telegraph
The Metz – Landau optical telegraph line dates back to 1793. In 1998, two reconstructions of optical telegraphs were built in Saarland at their presumed historical location in the southern Saarpfalz district in the municipality of Mandelbachtal near Neuhof near Bebelsheim and in the town of Blieskastel in Biesingen by a support group chaired by local historian Günter Wolf. Another reconstruction was created in Cadenbronn in France. When the weather is clear, the three systems have visual contact so that they can communicate with each other using optical telegraphy.
On the Kochersberg in Alsace there is an immovable monument on the site of a former telegraph tower on the Paris – Strasbourg line.
At Saverne in the Haut-Barr in Alsace a historical, partly reconstructed station can be visited.
Late military use
On the British Mark V tank , which was introduced in spring 1918, there was a sliding, rotating semaphore with two beeper trowels for transmitting messages.
Signal system of the railways
From the optical telegraph system of the transmission of a message from one place to another place, the signaling of the railways was differently derived around 1850 by each railway company, which is still valid today when modernized. A message or instruction is transmitted by means of optical signal images between a dispatcher or train driver or shunter and a train driver and vice versa by means of the signal images at the top of the train "peak signal" and at the end of the train "final signal" by colored lamps or by boards to a stationary dispatcher . The optical signal system of the railways has not been replaced, but only supplemented by electronic signals such as linear train control , cellular telephony and remote-controlled operation.
A greatly simplified form of communication was also the transfer of a staff or ring, which allowed the driver who owned it to use the route alone, as on English railways or trams.
Until 1907, each railway company had its own rules. Each standardization was recommendatory and developed only piecemeal, with one country, one company, one supplier being more progressive than another. The Kingdom of Prussia had played a certain pioneering role, on the one hand in the amalgamation of many small principalities, on the other hand in the nationalization of private railway companies, especially because progressive company founders set up their production in Prussian Berlin , such as Werner von Siemens in 1847, the "Telegraphen Bau-Anstalt von Siemens & Halske in Berlin".
A major advantage of signaling in railway operations is that only a relatively short line of sight has to be covered, a maximum of 1,000 meters in a straight line in front of a main signal. If the unobstructed view is obstructed by a curve or a building or if the braking distance of a train is longer at the maximum permitted speed, the signal aspect of the main signal is sent ahead by an advance signal with its own signal aspect. In this way, a train driver can prepare for the message at the place where a signal is set up, even when visibility is poor.
The successive technical improvements in Morse code from the 1830s onwards heralded the end of the era of the opto-mechanical telegraph. Morse code telegraphy was many times faster (higher symbol rate ), easier and cheaper to build and maintain than the optical telegraph, less susceptible to interference and not dependent on the weather or time of day. The detachment did not take place abruptly, but gradually. Both systems coexisted for almost two decades. In 1853, the last optical telegraph line in France ceased; in Sweden , optical telegraphs continued to operate until 1880.
In 1859 Martha Coston (1826–1904) received a patent (No. 23,596) for the system of pyrotechnic signals that she had developed over a decade and that is still an integral part of communication at sea and on land in the United States Navy . Martha Coston founded her own companies, the Coston Signal Company and the Coston Supply Company, which were in operation until 1985. Their invention played an important role, especially in the Civil War .
Laser connections for data occasionally represent modern means of communication in competition with radio connections.
Telegraphy and Time
The effects of telegraphy are of epoch-making importance for the general awareness of space and time. Until then it had been taken for granted that a greater distance could only be overcome in a correspondingly long time. Telegraphic communication required strict adherence to agreed normal times so that signals could be observed on time. In Prussian telegraphy, for example, the Berlin time applied everywhere, which differs from the West German true solar time by up to 20 minutes. Every day at 7 p.m. a time signal was sent from Berlin to Koblenz, which arrived there after a few minutes.
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