The Prussian Semaphore System was a telegraphic communications system used between

Berlin Berlin ( , ) is the capital and largest city of Germany by both area and population. Its 3.7 million inhabitants make it the European Union's most populous city, according to population within city limits. One of Germany's sixteen constitue ...

and the

Rhine Province The Rhine Province (german: Rheinprovinz), also known as Rhenish Prussia () or synonymous with the Rhineland (), was the westernmost province of the Kingdom of Prussia and the Free State of Prussia, within the German Reich, from 1822 to 1946. It ...

from 1832 to 1849. It could transmit administrative and military messages by optical signal over a distance of nearly . The telegraph line comprised 62 stations each furnished with a signal mast with six cable-operated arms. The stations were equipped with telescopes that operators used to copy coded messages and forward them to the next station. Three dispatch departments (telegraphische Expeditionen) located in

Cologne Cologne ( ; german: Köln ; ksh, Kölle ) is the largest city of the German western States of Germany, state of North Rhine-Westphalia (NRW) and the List of cities in Germany by population, fourth-most populous city of Germany with 1.1 m ...

and

Koblenz Koblenz (; Moselle Franconian language, Moselle Franconian: ''Kowelenz''), spelled Coblenz before 1926, is a German city on the banks of the Rhine and the Moselle, a multi-nation tributary. Koblenz was established as a Roman Empire, Roman mili ...

handled the coding and decoding of official telegrams. Although

electric telegraph Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems ...

y made the system obsolete for military use, simplified

semaphore Semaphore (; ) is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arra ...

s were still used for

railway signals A railway signal is a visual display device that conveys instructions or provides warning of instructions regarding the driver’s authority to proceed. The driver interprets the signal's indication and acts accordingly. Typically, a signal mi ...

Historical background

At the time of construction of the

Prussia Prussia, , Old Prussian: ''Prūsa'' or ''Prūsija'' was a German state on the southeast coast of the Baltic Sea. It formed the German Empire under Prussian rule when it united the German states in 1871. It was ''de facto'' dissolved by an em ...

n semaphore system, the technology had already been known for thirty years. It was based on earlier designs by

Claude Chappe Claude Chappe (; 25 December 1763 – 23 January 1805) was a French inventor who in 1792 demonstrated a practical semaphore system that eventually spanned all of France. His system consisted of a series of towers, each within line of sight of ...

and his brother which were in use in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

on many telegraph lines from 1794. Soon

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Danish Realm, Kingdom of Denmark ...

, and

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also had working optical telegraph systems while couriers remained in use throughout Germany. The states that existed in German-speaking areas at the end of the 18th century were uninterested in a communications system that crossed multiple borders and the political conditions did not exist to put the necessary treaties and agreements in place among these states. Countries such as Sweden, England and France had the necessary centralized control for such a project, and they confronted political, military and economic challenges such as securing long coastlines, and controlling sea routes. They were therefore far more motivated to build an advanced communications network. Prussia was at that time the second largest German state in terms of area and it saw no structural or political necessity for the introduction of telegraphy after the

Congress of Vienna The Congress of Vienna (, ) of 1814–1815 was a series of international diplomatic meetings to discuss and agree upon a possible new layout of the European political and constitutional order after the downfall of the French Emperor Napoleon B ...

of 1814-1815. Plans for the construction of a first telegraph line were delayed by resistance from the conservative Prussian military, even when the usefulness of mobile telegraphy in war is taken into account. It was exactly this technology that was used with success by

Napoleon Bonaparte Napoleon Bonaparte ; it, Napoleone Bonaparte, ; co, Napulione Buonaparte. (born Napoleone Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French military commander and political leader who ...

and this at least awakened the interest of the Prussian military. However, Prussia was confronted with a fragile domestic political situation in its western provinces at the beginning of the 1830s. Nobles and liberals from the

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region were opposed to the administration in Berlin. They were strengthened in their movement for a national constitution by the

July Revolution The French Revolution of 1830, also known as the July Revolution (french: révolution de Juillet), Second French Revolution, or ("Three Glorious ays), was a second French Revolution after the first in 1789. It led to the overthrow of King ...

in France and the revolution in Belgium in 1830. In this time of turmoil, urgent official messages traveled slowly by courier on horseback. This was unsatisfactory to the Prussian military, therefore, the proponents of a telegraph network could finally execute a plan for a line from Berlin to Koblenz via Cologne. The technical idea and the initiative to build the then longest telegraph line in central Europe came from the Geheime Postrat Carl Philipp Heinrich Pistor. Pistor wrote a

memorandum A memorandum ( : memoranda; abbr: memo; from the Latin ''memorandum'', "(that) which is to be remembered") is a written message that is typically used in a professional setting. Commonly abbreviated "memo," these messages are usually brief and ...

to the

Prussian General Staff The German General Staff, originally the Prussian General Staff and officially the Great General Staff (german: Großer Generalstab), was a full-time body at the head of the Prussian Army and later, the German Army, responsible for the continuou ...

in December 1830 which laid out a draft proposal for a telegraph line within the Royal Prussian States. Pistor’s ideas were inspired by the Englishman Bernard L. Watson whose designs were based on the "Second Polygrammatic Telegraph" of

William Pasley William is a male given name of Germanic origin.Hanks, Hardcastle and Hodges, ''Oxford Dictionary of First Names'', Oxford University Press, 2nd edition, , p. 276. It became very popular in the English language after the Norman conquest of Eng ...

. The design went back to 1810 and consisted of a mast with six telegraph arms. Pistor took the six-arm principle and thoroughly reworked the mechanics of the construction. Further, his workshop developed the optical telescopes which were a necessary component of the system. The order for the construction of the system was finally given by an order of the Prussian Cabinet on 21 July 1832. The Prussian system remained the only state-run optical telegraph system within German territory. There were also a couple of examples of privately run systems. The first existed between 1837 and 1850 and was created by the Altona businessman Johann Ludwig Schmidt who operated it as a signal system for ships between the mouth of the

Elbe The Elbe (; cs, Labe ; nds, Ilv or ''Elv''; Upper and dsb, Łobjo) is one of the major rivers of Central Europe. It rises in the Giant Mountains of the northern Czech Republic before traversing much of Bohemia (western half of the Czech Repu ...

Cuxhaven Cuxhaven (; ) is an independent town and seat of the Cuxhaven district, in Lower Saxony, Germany. The town includes the northernmost point of Lower Saxony. It is situated on the shore of the North Sea at the mouth of the Elbe River. Cuxhaven has ...

and

Port of Hamburg The Port of Hamburg (german: Hamburger Hafen, ) is a seaport on the river Elbe in Hamburg, Germany, from its mouth on the North Sea. Known as Germany's "Gateway to the World" (''Tor zur Welt''), it is the country's largest seaport by volume ...

. From 1841, this system was run by

Friedrich Clemens Gerke Friedrich Clemens Gerke (22 January 1801 – 21 May 1888) was a German writer, journalist, musician and pioneer of telegraphy who revised the Morse code in 1848. It is Gerke's version of the original (American) Morse code now known as the Interna ...

, a pioneer in telegraphy for whom the modern

telecommunications tower Radio masts and towers are typically tall structures designed to support antennas for telecommunications and broadcasting, including television. There are two main types: guyed and self-supporting structures. They are among the tallest human-made ...

in Cuxhaven is named. The second, also created by Schmidt was inaugurated in 1847. This system ran between

Bremen Bremen (Low German also: ''Breem'' or ''Bräm''), officially the City Municipality of Bremen (german: Stadtgemeinde Bremen, ), is the capital of the German state Free Hanseatic City of Bremen (''Freie Hansestadt Bremen''), a two-city-state consis ...

and

Bremerhaven Bremerhaven (, , Low German: ''Bremerhoben'') is a city at the seaport of the Free Hanseatic City of Bremen, a state of the Federal Republic of Germany. It forms a semi-enclave in the state of Lower Saxony and is located at the mouth of the Riv ...

, but this second system was taken out of service by 1852 because a competing

line that was placed into service at almost the same time.

Construction and function

As with later telegraph operations, the responsibility for the construction of the entire system fell to the Prussian Military. Major Franz August O'Etzel led the construction. O'Etzel studied in Berlin and Paris and trained as pharmacist. He knew the

Rhineland The Rhineland (german: Rheinland; french: Rhénanie; nl, Rijnland; ksh, Rhingland; Latinised name: ''Rhenania'') is a loosely defined area of Western Germany along the Rhine, chiefly its middle section. Term Historically, the Rhinelands ...

as he had previously done survey work in the region. Along with the construction, O'Etzel also concerned himself with the necessary codes for transmitting messages. He wrote the

codebook A codebook is a type of document used for gathering and storing cryptography codes. Originally codebooks were often literally , but today codebook is a byword for the complete record of a series of codes, regardless of physical format. Cryptog ...

s for the line. Once construction was complete, he was given the title of "Director of the Royal Prussian Telegraph" and he oversaw the operations of the entire system.

Route

The line began with Station 1 at the old

Berlin Observatory The Berlin Observatory (Berliner Sternwarte) is a German astronomical institution with a series of observatories and related organizations in and around the city of Berlin in Germany, starting from the 18th century. It has its origins in 1700 w ...

in Dorotheenstrasse. The construction of the first section – with fourteen stations – was completed by November 1832. The route ran via the Telegraphenberg 4 in

Potsdam Potsdam () is the capital and, with around 183,000 inhabitants, largest city of the German state of Brandenburg. It is part of the Berlin/Brandenburg Metropolitan Region. Potsdam sits on the River Havel, a tributary of the Elbe, downstream of B ...

across

Brandenburg an der Havel Brandenburg an der Havel () is a town in Brandenburg, Germany, which served as the capital of the Margraviate of Brandenburg until it was replaced by Berlin in 1417. With a population of 72,040 (as of 2020), it is located on the banks of the H ...

Magdeburg Magdeburg (; nds, label=Low Saxon, Meideborg ) is the capital and second-largest city of the German state Saxony-Anhalt. The city is situated at the Elbe river. Otto I, the first Holy Roman Emperor and founder of the Archdiocese of Magdebur ...

. The locations of the stations were chosen by O'Etzel himself. In choosing, he took into consideration of existing structures - for example the village church in Dahlem. He also had his team construct towers on existing tall buildings. In many places along the route, trees had to be felled or have their tops cut off in order to maintain the sight lines between stations. French telegraph operators had already recognized that signals were hard to recognize if they came from stations placed before certain backgrounds, while signals from stations against an open sky were much easier to recognize. For this reason, the Prussian stations were built on higher ground where necessary. Later, such places were often designated as "Telegrafenberg" as with Glidow (station 5) or station 13 southeast of

Biederitz Biederitz is a municipality in the Jerichower Land district, in Saxony-Anhalt, Germany. It consists of the following ''Ortschaften'' or municipal divisions:Johannis-Kirche in

. To hasten construction of the second and longer section between Magdeburg and Koblenz, the finance minister as well as the interior minister ordered all their subordinates to offer their total cooperation to the construction leadership. This was done to avoid time-consuming territorial conflicts between local authorities. If an agreement over the acquisition of a piece of land for the construction of a new station was not possible, expropriation of private lands could be undertaken in the worst case. The line ran north of

Egeln Egeln () is a small town in the Salzlandkreis district, in Saxony-Anhalt, Germany. It is the administrative seat of the ''Verbandsgemeinde'' ("collective municipality") Egelner Mulde. Geography Egeln is situated on the river Bode (river), Bode, ...

( Schloss Ampfurth), through

Halberstadt Halberstadt ( Eastphalian: ''Halverstidde'') is a town in the German state of Saxony-Anhalt, the capital of Harz district. Located north of the Harz mountain range, it is known for its old town center that was greatly destroyed by Allied bombi ...

Goslar Goslar (; Eastphalian: ''Goslär'') is a historic town in Lower Saxony, Germany. It is the administrative centre of the district of Goslar and located on the northwestern slopes of the Harz mountain range. The Old Town of Goslar and the Mines ...

Höxter Höxter () is a town in eastern North Rhine-Westphalia, Germany on the left bank of the river Weser, 52 km north of Kassel in the centre of the Weser Uplands. The main town's population is around 15,000, and with outlying centres, about 30,0 ...

to station 31 near Entrup where it turned in a southwesterly direction just before reaching

Paderborn Paderborn (; Westphalian: ''Patterbuorn'', also ''Paterboärn'') is a city in eastern North Rhine-Westphalia, Germany, capital of the Paderborn district. The name of the city derives from the river Pader and ''Born'', an old German term for t ...

after crossing the

Weser Uplands The Weser Uplands (German: ''Weserbergland'', ) is a hill region in Germany, between Hannoversch Münden and Porta Westfalica, along the river Weser. The area reaches into three states, Lower Saxony, Hesse, and North Rhine-Westphalia. Important ...

. Subsequently, it ran along the southern side of a line connecting

Salzkotten Salzkotten is a town in the district of Paderborn, in North Rhine-Westphalia, Germany. The name Salzkotten (in English, "Salt cottages") is based in the former salt production, which gave Salzkotten its raison d'être. Salt was found in the salty ...

Erwitte Erwitte () is a town in the district of Soest, in North Rhine-Westphalia, Germany. Geography Erwitte is situated approximately 8 km south of Lippstadt and 15 km east of Soest. Neighbouring municipalities * Lippstadt * Geseke * Rüt ...

, Soest,

Werl Werl (; Westphalian: ''Wiärl'') is a town located in the district of Soest in North Rhine-Westphalia, Germany. Geography Werl is easily accessible because it is located between the Sauerland, Münsterland, and the Ruhr Area. The Hellweg road ...

Iserlohn Iserlohn (; Westphalian: ''Iserlaun'') is a city in the Märkischer Kreis district, in North Rhine-Westphalia, Germany. It is the largest city by population and area within the district and the Sauerland region. Geography Iserlohn is locat ...

Hagen Hagen () is the Largest cities in Germany, 41st-largest List of cities and towns in Germany, city in Germany. The municipality is located in the States of Germany, state of North Rhine-Westphalia. It is located on the south eastern edge of the R ...

Schwelm Schwelm is a town in the district of Ennepe-Ruhr-Kreis in the administrative region of Arnsberg within the state of North Rhine-Westphalia. Geography Schwelm is situated in the southeast of the "''Ruhrgebiet''", the Ruhr district of Germany, be ...

and

Lennep Remscheid () is a city in North Rhine-Westphalia, Germany. It is, after Wuppertal and Solingen, the third-largest municipality in Bergisches Land, being located on the northern edge of the region, on the south side of the Ruhr area. Remscheid ha ...

it made its way finally to

via the stations Schlebusch (station 49), and Flittard (50). From there he route ran parallel to the east bank of the

via

Spich Troisdorf () is a city in the Rhein-Sieg-Kreis (district), in North Rhine-Westphalia, Germany. Geography Troisdorf is located approximately 22 kilometers south of Cologne and 13 kilometers north east of Bonn. Division of the city Troisdorf consi ...

Ehrenbreitstein Ehrenbreitstein Fortress (german: Festung Ehrenbreitstein, ) is a fortress in the German state of Rhineland-Palatinate, on the east bank of the Rhine where it is joined by the Moselle, overlooking the town of Koblenz. Occupying the position of an ...

. The final station (60) was built into the

Ehrenbreitstein Fortress Ehrenbreitstein Fortress (german: Festung Ehrenbreitstein, ) is a fortress in the German state of Rhineland-Palatinate, on the east bank of the Rhine where it is joined by the Moselle, overlooking the town of Koblenz. Occupying the position of an ...

. After the completion of construction and the start of operations of the whole system in 1833, it quickly became clear that the Rhine ferry crossing to Koblenz presented a major hold up in telegraphic traffic. This could only be solved by expanding the line with an end station in Koblenz. In the same year, station 61 was put into service in the Electoral Palace in Koblenz, which was then used as a barracks. The palace also served as the administrative offices for the western section of the route. The route traveled over Hanoverian domain at stations 22 and 23 in

Schladen Schladen is a village and a former municipality in the Wolfenbüttel (district), district of Wolfenbüttel, in Lower Saxony, Germany. Since 1 November 2013, it is part of the municipality Schladen-Werla. It is situated on the river Oker, approx. 15 ...

and

Liebenburg Liebenburg is a municipality in the district of Goslar, in Lower Saxony, Germany. Geography The municipal area is situated north of the Harz mountain range, within the eastern Salzgitter Hills of the Innerste Uplands. It borders on the distri ...

. Likewise, stations 23 to 28 lay in the domain of the

Duchy of Brunswick The Duchy of Brunswick (german: Herzogtum Braunschweig) was a historical German state. Its capital city, capital was the city of Braunschweig, Brunswick (). It was established as the successor state of the Principality of Brunswick-Wolfenbüttel ...

. Negotiations with both governments for the acquisition of land and the construction of stations quickly met with success. Additionally, two stations were economized within the Brunswick domain by increasing the distance between stations 23, 24, and 25. After a year of service, it became clear that the wide interval between these stations led to frequent interruptions in visual contact during drizzly and grey weather. In 1842 this problem was solved with the construction of station 24a near Mechtshausen. The entire route now comprised 62 stations. They were on average apart with the longest distance separating stations at and the shortest at . There were only two dispatch stations, one at each end of the line. Koblenz was the seat of the

Oberpräsident The ''german: Oberpräsident, label=none'' (Supreme President) was the highest administrative official in the Prussian provinces. History The Oberpräsident of a Prussian province was the supreme representative of the Prussian crown, until its ...

of the Rhine Province and the western headquarters of the Prussian defense force. Messages could neither be sent nor received from the obviously larger and more important economic and transportation center of Cologne. Messages arriving in Cologne from England or

Belgium Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...

addressed to Berlin had to first be sent by courier to Koblenz and then from there telegraphed again through Cologne to Berlin. This whole process caused a day’s delay. Hence, in 1836, a third dispatch bureau was opened at the Cologne telegraph station of St. Pantleon. Preussischer optischer Telegraf

Stations

The common functional element of all of the telegraph stations was the ca. high softwood mast. The mast carried the six telegraph arms - also known as indicators - and it also held the control mechanism for the arms. A ring was fastened between the top two sets of signal arms to which was attached four cables that were secured to the four corners of the station roof. This provided additional stability to the mast during storms. The mast and control mechanism ran through the roof of the observation room. The roof was specially sealed against rain. The mast was secured to the floor beams and likewise the roof with

cast iron Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...

hardware.

Indicators and their control

The moving signal arms were suspended with counterweights to enable easy adjustment. The indicators measured 1.74 m × 0.33 m. Only two of the original indicators still exist today; one is on display in the Boerdemuseum in Ummendorf and the other in the Museum for Communication in Berlin. These arms, as well as preserved construction drawings, suggest that the arms consisted of a wooden framework with a wood or sheet metal interior. This provided greater wind resistance. The operating mechanism of the system was located at the bottom of the mast in the observation room of the station. The indicators were operated with six adjustable levers arranged above each other in pairs. The position of each lever corresponded to the three-level alignment of the signal arms on the mast above. The levers and signal arms were connected by hemp ropes and later by wire cables. The levers each were lockable in four different positions, that exactly corresponded to the position of signal arm: 0° (arm hanging downward parallel to the mast), 45°, 90° (perpendicular to the mast), and 135°. Each position was relative to the mast.

Scopes

Each station had two telescopes for observing the neighboring stations. The scopes were either of English construction or they came from Pistor’s workshop. The portion of the route between Cologne and Koblenz was outfitted chiefly with scopes from the Munich lens-maker

Georg Merz Georg Merz (26 January 1793 – 12 January 1867) was a Kingdom of Bavaria, Bavarian optician and manufacturer of astronomical telescopes and other optical instruments. Life Merz was born on 26 January 1793 in Bichl, in Bad Tölz-Wolfratshause ...

. The scopes’ magnification is estimated at between 40 and 60x. As with the other technical aspects of the stations, very specific instructions existed at each for the storage, use, and care of the scopes. Twelve paragraphs of instruction were allotted to the scopes alone.

Station clocks and time synchronization

"Berlin Time" was the authoritative time used along the entire telegraph line; with a time-synchronizing message coming from Berlin every three days at the latest. A Schwarzwald Clock with a chime hung in each station as the official station clock. The synchronization process would be announced an hour in advance with a signal which prompted the station agents to continuously observe the neighboring station in the direction of Berlin. The signal had to then be sent to the next station without delay. Once the signal reached Koblenz, it was relayed back to Berlin as confirmation. In good weather conditions, the entire process from Berlin to Koblenz and back took less than two minutes. With such a synchronization process, the time difference amounted to less than one minute.