Prussian optical telegraph
The Prussian optical telegraph was a telegraphic communication system between Berlin and the Rhine Province that existed between 1832 and 1849 , which could transmit official and military messages by means of optical signals over a distance of 588 kilometers. The telegraph line consisted of up to 62 telegraph stations, which were equipped with signal masts, each of which had six telegraph arms that could be operated with cables. The stations were equipped with telescopes with which telegraph operators read specially coded information from a signaling station and passed it on immediately to the next one. Three telegraphic expeditions (dispatch departments) in Berlin, Cologne and Koblenz enabled the reception, encryption , decryption and issue of state dispatches .
The Prussian optical telegraph was the longest telegraph line in Europe in its time. The system is referred to as the beginning of telecommunications in Germany, although 19 years earlier the French optical telegraph line Metz – Mainz led through later German territory. The " Berlin time " of the Prussian optical telegraph, synchronized over the entire line, was the first uniform time level at such a great distance with a tolerance of around one minute.
The system became superfluous with the introduction of electrical telegraphy . Even if no messages are telegraphed by optical means, the principle is still used with the winker alphabet and, in a greatly simplified form, with mechanical railway signals.
During the construction of the Prussian telegraph line, the technology of opto-mechanical telegraphy had been known for over 30 years: Based on the construction of Claude Chappe and his brothers, it was in practical use in France on several telegraph lines from 1794.
Even Sweden , Denmark and England soon run out optical telegraph , while in Germany piece messages were still carried by messengers. The small and sub-states that existed on German territory at the end of the 18th century showed no interest in communication technology that transcended their own sovereign territory, nor were there the political conditions for the necessary agreements and arrangements. In countries like Sweden, England or France, on the other hand, there was not only the necessary national unity for such a project; They were also confronted with political, military and economic challenges such as securing long coastlines, controlling maritime trade or the political situation after the French Revolution and were therefore motivated and able to set up telegraphic communication networks.
Prussia, the second largest German state at the time, saw no structural or political need for the introduction of telegraphy until the territorial reorganization of the Congress of Vienna of 1814/1815. Even after that, the implementation of plans to build a first telegraph line was delayed again and again due to resistance from the conservative Prussian military system. If at all, the use of this new communication technology was considered at best in the context of a mobile field telegraph for military operations. Field telegraphy in particular had been used successfully by Napoléon Bonaparte , which at least aroused the interest of the military.
However, at the beginning of the 1830s one was confronted with a fragile domestic political situation in the Prussian western provinces - Rhenish liberals and nobles opposed the Berlin state administration, their constitutional movement strengthened by the French July Revolution and the Belgian Revolution of 1830. Urgent state dispatches in this situation The Prussian military found it increasingly unsatisfactory to transmit at the slow speed of mounted messengers, which is why the advocates of a fixed telegraph line from Berlin via Cologne to Koblenz were ultimately able to prevail.
The technical idea and initiative to build what was then the longest telegraph line in Central Europe came from the Berlin secret postal councilor Carl Philipp Heinrich Pistor , who in December 1830 submitted a memorandum to the Prussian General Staff on the draft for the construction of a telegraph line in the Royal Prussian States. Pistor's construction of the telegraph apparatus was inspired by the devices of the Englishman Barnard L. Watson, who in turn was based on the "Second Polygrammatic Telegraph" by William Pasley, a mast with six telegraph arms from 1810. Pistor adopted the six-arm principle and revised the mechanics of the Construction but comprehensive. In addition, his workshop developed the telescopes required for operation, which were later also produced by Pistor. With a cabinet order of July 21, 1832, the construction of the plant was finally ordered, which marked the beginning of telecommunications in Germany.
The Prussian system remained the only state optical telegraph on German soil. Between 1837 and 1850 the Altona merchant Johann Ludwig Schmidt operated an optical telegraph between the mouth of the Elbe in Cuxhaven and Hamburg as a ship reporting service . From 1841 this system was managed by Friedrich Clemens Gerke , a pioneer of telegraphy. Schmidt also opened an optical telegraph between Bremen and Bremerhaven in 1847 , which, however, went out of service in 1852 due to competition from an electric telegraph line that was in operation almost simultaneously on the same route.
Layout and function
Like the later operation, the construction of the facility was the responsibility of the Prussian military. Major Franz August O'Etzel directed the construction . The trained pharmacist and doctor of philosophy, who studied in Berlin and Paris, knew the Rhineland, where he had previously been entrusted with surveying work. In addition to the construction management, he also dealt with the codes and methods required for telegraphic correspondence and wrote the code books of the telegraph line. As the “Royal Prussian Telegraph Director”, he also managed the operation of the system.
The telegraph line began at the old Berlin observatory in Dorotheenstrasse, station 1. The first construction phase with 14 stations was completed by November 1832. The route ran over the Potsdam Telegrafenberg and Brandenburg an der Havel to Magdeburg .
The locations of the stations were selected by O'Etzel himself. He took into account existing structures such as the tower of the Dahlem village church (station 2), or he had correspondingly high buildings or towers erected.
In order to ensure visual contact on the route, trees had to be cut down and felled in some places. The French telegraph operators already realized that the signal systems were difficult to see and read against some fixed backgrounds, but easy to see against the open sky. Where necessary, the Prussian stations were therefore built on elevated terrain. Such places were later often referred to as "Telegrafenberg", also at Glindow (Station 5) or at Station 13, southeast of Biederitz . Since the reception and output of telegraphic messages was only provided for by the expeditions (dispatch department) at the beginning and end of the telegraph line, no great importance was attached to the connection of towns and cities; often the telegraph stations were outside of populated areas. The last station of the first section was set up at the Johannis Church in Magdeburg .
In order to accelerate the second, longer construction phase between Magdeburg and Koblenz, the Minister of Finance, the Minister of the Interior and the Police instructed all subordinate local authorities to cooperate extensively with the construction management in order to avoid lengthy court cases and arguments. If it was not possible to agree on the acquisition of land to build a telegraph station, in the worst case scenario, private individuals could be expropriated . The line ran north of Egeln ( Ampfurth Castle ), Halberstadt , Goslar , Höxter to Station 31 near Entrup, where it bent southwest after crossing the Weser Uplands before Paderborn . It then ran on the southern side along the Salzkotten , Erwitte , Soest , Werl , Iserlohn , Hagen , Schwelm and Lennep axis and finally found its way to Cologne via the stations in Schlebusch (49) and Flittard (50) . From there, the route ran on the east side parallel to the Rhine via Spich to Ehrenbreitstein . Integrated into the fortress there , station 60 was the intended end point of the route. After the completion and commissioning of the entire system in 1833, however, it quickly became apparent that the ferry crossing of the Rhine to Koblenz represented a considerable delay in telegraphic traffic, which could only be avoided by expanding the line to include a terminal in Koblenz. This station 61 was placed in the same year, together with the rooms for the administration of the western section of the route, in the Koblenz Electoral Palace , which was then used as barracks .
With the two stations Schladen (No. 22) and the Stofenberg near Liebenburg -Lewe (No. 23), the telegraph line also ran a bit through the Hanoverian area. The stations 24-28 were in the area of the Duchy of Braunschweig . Negotiations with both governments about the purchase or lease of land and the construction of stations quickly led to success.
An attempt was made to save two stations in the Braunschweig area by increasing the distances between stations 23, 24 and 25. After one year of operation it was found that the large distance in cloudy weather led to frequent interruptions in visual contact. This problem was not solved until 1842 with the construction of an intermediate station, number 24 a near Altgandersheim .
The route thus comprised 62 telegraph stations. They were on average about 9.6 km apart, with the maximum distance being 16.0 km and the minimum being 2.1 km. The entire route covered a straight line distance of 469 kilometers, the actual route length was 588 km.
Initially there was only one expedition office (dispatch office) at each of the two endpoints of the route - Koblenz was the seat of the Upper President of the Rhine Province and the western headquarters of the Prussian defense system. In the city of Cologne, which has around 95,000 inhabitants and is significantly larger in terms of both economy and transport, neither messages could be received nor sent. Messages destined for Berlin from England or Belgium that arrived in Cologne first had to be sent by messenger to Koblenz and then telegraphed from there via Cologne to Berlin, which delayed them by a day. Therefore, in 1836, a third expedition office was finally opened at the St. Pantaleon telegraph station in Cologne .
A common functional element of all telegraph stations was the round coniferous mast tree, which protruded about 6.30 meters above an observation room. He carried the six telegraph arms, also called indicators, and he also ran the control trains. Mast and control cables were guided through the roof of the observation room with special seals against rain. The mast was attached to the floor framework of the observation room with a cast iron construction and also fixed in the roof opening. A ring was attached between the two upper pairs of indicators, to which four storm poles were attached, which were anchored at the corners of the station or tower roof. These poles gave the mast additional stability.
Indicators and their control
The six movable telegraph arms or indicators were attached to the mast in pairs and suspended with counterweights that ensure easy adjustment. Each pair formed one of three floors. The hands measured 1.74 × 0.33 m. In the original there are only two indicators left today, exhibited in the Bördemuseum Ummendorf and in the Museum for Communication in Berlin. These, as well as surviving construction drawings, suggest that the telegraph arms consisted of wooden frames with wooden or sheet metal blinds inside to offer less resistance to the wind.
The control of the system was on the lower part of the mast, in the observation room. Analogous to the indicators, there were six adjusting levers attached in pairs on control discs, which controlled the indicators via a wire rope and tie rod system. Their position and lever position corresponded exactly to the drawing on the indicators on top of the telegraph. The adjustment levers could be locked in four stages with pins, which corresponded exactly to the intended arm positions: 0 ° (wing hangs on the mast), 45 °, 90 ° and 135 °, each starting from the mast.
Each station had two telescopes for observing the neighboring telegraph stations. They were either English models, telescopes from the Pistor workshop or, especially on the section between Cologne and Koblenz, models from the Munich optician Georg Merz . Today, the magnification is estimated to be 40 to 60 times. In accordance with the importance of these tools for the system, the construction, installation, use, storage and maintenance of the telescopes were described in great detail in the instructions for the telegraph company. Chapter 5, “Treatment of the telescope” alone contained twelve paragraphs.
It contains, for example, the advice not to constantly look through the glass during use, but regularly only look through the glass four to five times per minute for a few seconds in order to avoid overexertion of the eye. In addition to the 122 telescopes in permanent operation in the stations, the system was equipped with six reserve telescopes during the inspections.
Station clocks and time signal
The so-called "Berlin time" was decisive for the entire telegraph line, which was telegraphed from Berlin at least every three days to synchronize all stations. A Black Forest clock with a striking mechanism hung in each station as a station clock . The synchronization process was announced an hour in advance by signs, which caused the telegraph officers to constantly observe the neighboring station from Berlin at the time of synchronization and to forward the time signal B 4 immediately. When I arrived in Koblenz, a confirmation signal was immediately sent in the opposite direction. In good weather conditions, the transmission of a time signal from Berlin to Koblenz, including the feedback to Berlin, took less than two minutes. The time difference within the scope of such a synchronization was then less than a minute. So this time signal was not only the fastest communication signal available at the time. With a time difference of less than a minute, the “Berlin time” was also the first uniform time level at such a large distance.
If the telegraph stations were not integrated into existing buildings, five different basic types of station buildings were built, between which were selected and varied depending on the location, the expected needs of the company and the ideas of the garrison construction directors commissioned with the construction in sections:
- 1) Small station houses were mainly built in the first construction phase. They served exclusively as a workplace for two telegraph operators.
- 2) Station towers with a comparable floor plan also only offered space for the exercise of the telegraph service. They emerged from station houses that were raised to avoid obstructions by air flickering near the ground, or they were built on several floors to tower over obstacles.
Especially in the second construction phase, apartments for the telegraph operators and their families were included in the construction, as many stations were built away from settlements and long journeys to work were to be avoided as well as a separation of the officials from their families. The residential buildings usually had two rooms, two kitchens and several chambers, as two families of telegraph operators lived there. Such stations often included a garden that was used for the self-sufficiency of the people living there. Stations with residential buildings were part of the
- 3) "House-tower type" with a closed tower integrated into the building (as in Flittard, see illustration at the beginning of the article)
- 4) " Gable roof type" with attached or free-standing tower
- 5) " Hipped roof type", also with an attached tower, but different roof construction
The residential and station buildings were, with the exception of the subsequently built station 24a with two floors, one-story. The attic was developed and habitable. In sections, stations had storage rooms for spare parts for the pointing device. Others owned stables for horses, with which messengers could bridge sections of the route for urgent messages if the line of sight was lost or the telegraph was damaged. The buildings were erected in a simple, functional style, with the exterior design and construction varying with the locally available materials and the techniques mastered by the craftsmen: half-timbered with brick lining , quarry stone construction and brick masonry with and without plaster cladding were used. If an exterior paint was applied, colors that stood out from the surroundings were generally used in order to improve the visibility of the station.
In addition to the telegraph stations already mentioned in the old Berlin observatory, the Dahlem village church and the Magdeburg Johanniskirche, three further stations were integrated into existing public or church buildings:
- Station 16 on the castle tower of Ampfurth Castle
- Station 51 on the central tower of the St. Pantaleon Church in Cologne - the church building then served as a Protestant garrison church. This made the reconstruction of the tower possible, in which at least the entire baroque gable helmet of the tower was removed and an observation room was installed underneath.
- Station 61 at the Electoral Palace in Koblenz .
All telegraph stations were manned by an upper and a sub-telegraph operator, who carried out the telegraph service during the day when there was sufficient daylight.
Messages from the telegraph expeditions in Berlin, Koblenz and later also in Cologne were recorded in the dispatch operation. In the encryption offices there, the officials had secret code books for state dispatches, which are no longer preserved today. The messages encrypted there were sent over the telegraph line and only converted back into plain text in the encryption office of the destination and delivered by the telegraph expedition. Each telegraph station acted like a relay - messages were only read in encrypted form and passed on in the same way. State dispatches could not be accepted, encrypted or sent in the stations, and decryption was not planned either.
On the other hand, operational and official messages, such as status reports or the notification of faults, could be transmitted between the telegraph expeditions and the stations independently of the state cables. For this purpose, the telegraph operators at all stations had a “Dictionary for Telegraphist Correspondence” of “Class 5.2” at their disposal.
From six telegraph arms, which could take four positions with the angles 0 ° (zero position, hanging on the mast), 45 °, 90 ° and 135 °, the mathematical possibility arose to represent = 4096 characters, whereby the zero position of the entire telegraph ( Rest position) was not a symbol of its own in use. The O'Etzel code system used the character repertoire by writing the arm positions as code numbers from 0 to 999 as well as combinations of two digits (separated by a point):
The spelling of the code is derived from two clockwise pointers. With one of the two arms of an indicator pair in the zero position, the second indicator could take four positions (1, 2, 3, 0 or 0, 4, 5, 6). In this way, the code numbers 0 to 6 were displayed with just one indicator.
To represent the code numbers 7 to 9, two indicators were used at the same time: The left telegraph arm was placed in the position for 6 and at the same time the right arm in the positions for 1, 2 or 3, which resulted in the character positions 7, 8 and 9.
In addition, there were combinations of two indicators in which the right arm signaled 1, 2 or 3, while the left arm was placed in the position for 4 or 5. Such combined characters were read off as double digits and written down separated by a point, for example as "4.1" or "5.3".
For positioning and reading, the three floors were designated A, B and C, reading from bottom to top. The notation of a complete character position was then A [lower floor] B [middle floor] C [upper floor], for example "A5.3 B7 C4.3" - in the example the middle telegraph arms form the code number 7 while the upper and the bottom each form a combination (double digits). Each level of the signal mast with its indicator position represented a digit or double digit of the code number.
The control unit of the telegraph in the observation room reproduced the position of the telegraph arms in an analog manner. It had to be operated from both the Berlin and Koblenz sides and was labeled from both sides by floors (A. B, C) and the intended positions of the telegraph arms. The positions of the control levers (indicators to the right of the mast) on the Berlin side were labeled 1, 2, 3, 0 and those on the Koblenz side were labeled 6, 5, 4, 0. The setting / representation of the characters was the same, regardless of the direction in which the dispatch was transmitted. Reading from the neighboring stations, however, had to be mastered by the telegraph officers in two opposite directions, as the telegraph traffic ran in both directions. For this, intensive training and regular practice were prescribed and also necessary.
Business and official news
The "Dictionary for Telegraphist Correspondence" of "Class 5.2". is still preserved today. The inspectors and the management used the dictionary for administrative communication with the telegraph operators, for which they coded messages and decoded messages from the stations with the help of the book. All transmitting stations could read the content of the message in “Class 5.2”. The code book contained addressing options, part names of the telegraph, place names and proper names, syllables, words, sentences, numerals and time units. The beginning of messages from the stations of "Class 5.2" was initiated with a character position that represented the station number on floors A and B and the double digit 5.2 on C.
The code books were thematically structured and used tables to list the characters with their associated meanings. Where possible, words and parts of sentences that could be coded were used to avoid the time-consuming telegraphing of individual syllables and letters. This was then only used for proper names or less common words not contained in the code book. The texts were shortened beforehand by the long phrases and nobility predicates that were common in the correspondence of the time . The text length could be reduced to half of the original text. However, when decoding a message, a minimum of embellishments had to be reinserted. Punctuation was only medium-graphed when it was essential to understand sentences.
An example from the instruction book for telegraphists to practice this process according to "Class 5.2":
Draft of a typical message
"Sr. Royal The Highness of the Duke of Cambridge held a great hunt in the local forest and took this opportunity to inspect the K. Prussian Telegraph, which is not far from the Liebenburg office. Most of all, they gave the telegraphists present to recognize that they were pleased with the functional arrangement and the punctuality with which they performed their duties "
Removal of empty phrases, predicates of nobility and other filler words that were not required to understand the text:
"Duke Cambridge hunted in the local forest, inspected the telegraph, which is not far from Liebenburg, and gave the telegraphists their satisfaction with the functional equipment and punctuality in service"
Words that were not in the code book were replaced by encodable synonyms , whereby the original meaning of the text had to be retained:
"Duke Cambridge stopped here in the forest, hunting, was at station No 23, and was pleased with the good facilities and the punctual service of the telegraph"
Using a table with columns A, B and C for the floors of the telegraph and a column for the associated words, sentences or syllables, the message was coded using the code book. Announcement, closing and other necessary characters have also been added:
|2||3||5.2||Report from station No 23.|
|4.3||5.1||To the direction|
|7th||0||8th||Dispatch No. 8|
|9||4th||6th||has given to recognize|
Protocol and procedure
The transmission of telegrams and the administrative exchange between stations and the telegraph directorate were precisely regulated in a protocol , the second chapter of the "Instruction" for the telegraph operators:
- Both telegraph operators at one station monitored the two neighboring stations at regular, short intervals. When the line was idle, monitoring happened every minute, and several times a minute during the planned transmission phases. Uninterrupted observation was avoided so as not to overload the eyes.
- While the message was being transmitted, a telegraph operator observed the sending station and dictated the signal setting to the colleague in the order from A to C. The colleague set the levers accordingly and then checked the following station to see whether it had also correctly received and passed on his signal. The symbol was then entered in the station journal.
- In addition to the text of the message, every dispatch also included information on the date and time of departure from the expedition.
- Urgent messages were marked with the sign “B4.3 C4.3” for “Citissime!” ( Latin : fastest!). They were given preferential treatment and, in the event of a failure of sections of the line, conveyed to the nearest functioning station by messenger.
- To avoid overlaps, fixed hourly transmission times from Koblenz to Berlin were planned. If there was no more such message, the sign “A5.2 C5.2” - “Nothing new” was sent - then the dispatches should be telegraphed in the opposite direction. Idle times in between were provided for administrative messages from the stations.
- If two messages overlap in opposite directions, the procedure at the station in question was also precisely regulated so that both messages could first be recorded and then transmitted one after the other.
- For all conceivable special cases, such as the failure of a station, poor visibility conditions or incorrectly placed characters, the protocol contained procedural rules and regulations on the documentation of the incident.
After a message had been deciphered by an expedition office , it could be transmitted from there by a messenger to its addressee. Address books were available for the expeditions.
The operation of the Prussian optical telegraph originally served state purposes - private use was not intended and hardly possible due to capacity reasons. A request from the elders of Berlin's merchants in 1834 to be able to transmit at least important stock exchange prices and trade news was rejected . However, reports with political news, insofar as they were relevant to the level of trade, were published in the Prussian State Newspaper with the approval of the War Ministry and the Ministries for Police and Foreign Affairs.
The state purpose of the telegraph system initially comprised exclusively the internal and external military security of Prussia. The Ministry of the Interior and the police were only allowed to use it from 1835. Only then did the finance and foreign ministries participate in the use of the telegraph line, which soon reached its capacity limit.
At the end of the 1830s , a limited opening of the telegraph system to the press was noticeable when agreements were made with the Kölnische Zeitung and the Rhein-Mosel-Zeitung that certain telegraphic dispatches received for printing and the Berlin government in return with important international news reports via Telegraph should supply. Because the reports were subject to censorship before they were released and were also linked to the requirement for reports that were friendly to the monarchy, there were no significant advantages for the newspapers from this agreement. Politically explosive reports were not published, but irrelevant reports, for example about the king's trips, were readily made available to the newspapers.
At least a telegraphic report from the run-up to the March Revolution of 1848 has been handed down, which was made available to the Kölnische Zeitung. On March 17, 1848 at 5 p.m., a message was sent in Berlin, which arrived at the Cologne regional council at 6:30 p.m.
- “On three evenings the mob marched through the streets in troops. The citizenship was reassuring. Since yesterday everything is calm and there is no sign of renewal "
The news was published in a separate edition of the Kölnische Zeitung before the March Revolution broke out in Berlin a day later. The Chronik der Kölnische Zeitung commented on this publication with the words:
- “Up to now one had probably seen the telegraph stretching out its long arms high on the tower, but its work remained a book with seven seals to the people. So one was amazed when one held the extra sheet of the Kölnische Zeitung with that dispatch in one's hands. One wondered how quickly the thing could write, even though how badly it had stylized its essay ” .
Pieper quotes one of the few surviving examples of the practical benefits in an instruction from Interior Minister Gustav von Rochow on the treatment of the Belgian pastor Johannes Theodor Laurent , who was appointed (bishop-like) apostolic vicar in Hamburg , which he sent to the regional presidents in Cologne on February 3, 1840 , Aachen, Düsseldorf and Koblenz sent:
Copy of the Telegraphische Depesche
The Minister d. Interior and the police / v. Rochow /
His Maj. D. Kg. Have ordered that according to the content of the public. Leaves for the apostolic vicarius in Hamburg designated former pastor Laurent , who provided him with a passport from the Belgian authorities to Germany denying his spiritual dignity as a particulier sans profession / reverse side /, on 6th BC. M. (= January) arrived in Aachen and went from there via Düsseldorf to Koblenz, should only be treated by the local authorities in the quality that the passport encloses and that accordingly he should not be allowed to exercise clergy -To perform functions; In addition, however, since the passport from the pr. Embassy in Brussels was only intended for the transit to Aachen, the police were to be stopped, to continue his journey immediately and in any case to leave the royal states (Prß.) In which he could hardly be allowed to stay, to leave without delay.
In the event that dp Laurent is in the district there or wanted to arrive there, I want to arrange the necessary to carry out the foregoing Supreme Order in suitable ways and how this happens and wherever Laurent goes from there, by telegraphic View report here.
Posted 3 / 2.40.
When comparing the texts, the processing steps of the message are also clearly visible. The telegram sent by courier from the Berlin Ministry of the Interior to the Dorotheenstrasse telegraph expedition at 9:00 a.m. was processed and encrypted there in about three hours until it was telegraphed to the Rhine Province at 12:45 p.m. The actual telegraphed text is no longer available, but even the deciphered Cologne version of the telegraph with the most necessary empty phrases allows conclusions to be drawn about the considerable cuts that were made to the text. After deciphering in Cologne, the delivery to the messenger to Aachen took place at 10:00 p.m., that is, thirteen hours after the dispatch had been sent.
The daily operating time of the optical telegraph was about six hours in summer and about three hours in winter due to the lighting conditions. To assess the performance of the system, a distinction must be made between the speed of characters, the speed of correspondence and the effective performance of the system resulting from the speed of dispatches :
The fastest way to transmit a character over the entire route was achieved by synchronizing the station clocks: under good conditions, the synchronization character B 4, for which only one indicator had to be set, was on the move for less than a minute, for which the telegraph officers paid the greatest attention and appropriate preparation was required. In normal dispatch traffic, a sign ran through the route in 7½ to 14 minutes. As far as we know today, this drawing speed was somewhat slower than with the French system.
Findings about the speed with which correspondence characters were transmitted come from the records of Franz August O'Etzel. A station could read and set an average of 1.5 characters per minute. Two characters per minute were possible under extremely good conditions. In comparison, according to O'Etzel, the French telegraph transmitted almost twice as many characters per minute with a satisfactory view. He assumed that his system had twenty times the character repertoire of the French. In this way, the Prussian system compensated for the speed disadvantage of the correspondence signs, but could not exceed the speed of the French system. The French telegraph according to Claude Chappe actually only transmitted individual letters and only represented 92 signal constellations. By combining two consecutive signal positions (half characters), however, a maximum of 8464 codes for sentences, words, places, letters and numbers were later possible. That corresponded to more as the twofold repertoire of symbols of the Prussian system, which, however, set a complete symbol in just one step. The comparison of the effective correspondence speeds of both systems has not yet been adequately researched scientifically.
Dispatch speed and effective performance
Reliable records of the number of dispatches that can be sent daily are no longer available. The information fluctuates between two messages transmitted daily and the records of the telegraph director O'Etzel, who mentions up to six messages per day. At least the hourly transmission times that were regulated in the instructions for telegraph operators point to such frequent dispatch of the dispatches. Traditional dispatches with time indications indicate very different transmission services, presumably depending on weather conditions:
- February 2, 1840 - Telegram with 210 words from Berlin to Cologne: 13 hours
- March 17, 1848 - 30-word telegram from Berlin to Cologne: 1.5 hours
- August 11, 1848 - Telegram with 60–70 words from Berlin to Cologne: 8:00 p.m. to 10:30 a.m. of the next day after a break due to darkness (times from posting to delivery of the telegram to the delivering courier).
The transit time of a message is known from the administrative messages between the directorates and the individual stations:
- September 7, 1838 - Message with 29 words with congratulations between Koblenz and Station 9 ( Zitz Steinberg ): 30 minutes between 7:00 a.m. and 7:30 a.m.
Visible weather such as fog, rain or snowfall could seriously impair the visibility of the signal positions or even make it impossible. O'Etzel himself described weather-related interruptions in telegraph traffic for weeks between November 1840 and January 1841.
In the international telegram traffic, a message from Paris to Berlin, which was transmitted by the French telegraph to Metz , from there by messenger via Saarbrücken to Koblenz and then signaled to Berlin via the Prussian telegraph, took about 30 hours.
The telegraph corps responsible for the operation of the system was subordinate to the Chief of the Army General Staff, Johann Wilhelm von Krauseneck . The corps consisted of up to 200 military officials under the direction of the royal Prussian telegraph director. After the first director O'Etzel left office at short notice due to illness in 1848, major general and geodesist Johann Jacob Baeyer took over his post for a transitional period . In the same year he was replaced by Friedrich August von Etzel , son of the first telegraph director, during whose term of office the organization of the telegraph line was transferred from the War Ministry to the Ministry of Trade, Industry and Public Works.
The overarching supervision and control of the telegraph line was the responsibility of two chief inspectors in Berlin and Koblenz. The line itself was divided into seven inspections, each responsible for the operation of eight to ten telegraph stations.
In each station, an upper and a sub-telegraph operator was responsible for the telegraphic system. These officers were usually veteran military personnel, often of the rank of non-commissioned officer with a right to employment or care. In addition to a good technical understanding, the prerequisite for employment was mastery of the cultural techniques of writing, reading and arithmetic. In the first part of the "Instruction" for the telegraph operator, which describes the tasks of the telegraph officer, it also states:
- "A good telegraph clerk must be a man of healthy and unbiased judgment, who does not lack the spirit of observation (...) sobriety and a decent behavior in every respect are assumed as qualities without which the above-mentioned would lose most of their value".
The operation was supported by reserve telegraph operators, clerks and telegraph messengers.
The service conditions of the uniformed, sworn in and confidentiality officers were quite attractive for that time. In addition to the salary and the good opportunities for advancement within the corps, the offer to use the telegraph station as a residence for the telegraphist family led to a high demand for positions in the telegraph corps .
The annual earnings for a sub-telegraph operator were 210 thalers when the line opened; shortly before it was closed, it was 212 thalers. At this point in time, the senior telegraph operator received 285 and 312 thalers, respectively. 144 thalers were set for a reserve telegraph operator. The families were allowed to use the living quarters of the telegraph stations for 5% of the annual salary. In 1840, salaries of 500 thalers per station were calculated for the year. Major General O'Etzel received a regular income as an officer in the amount of 1,900 thalers, which was increased by 600 thalers due to his job as telegraph director. The chief inspector received 1118 thalers, which included travel expenses. The inspectors were each paid 818 thalers a year.
The total costs of the system were given for the year 1834 with 50178 thalers, for the year 1849 it was 53400 thalers. With an average broadcast time of 1440 hours per year, this results in costs of around 37 thalers for one broadcast hour in 1849.
Replacement by electrical telegraphy
The Prussian optical telegraph was an expensive and fragile technology with very limited transmission capacity, in spite of its enormous transmission speed compared to the personal conveyance of messages. In particular, darkness and weather-related obstructions to the view significantly restricted use. There are also reports of obstacles such as new buildings or trees that have regrown, each of which had to be removed at great expense and in some cases with payment of damages. Attacks on telegraph stations are also likely to have assumed a certain risk - an attack on a single station could have paralyzed the entire line. At least one such incident is documented, in which station 43 (Fröndenberg near Iserlohn ) was stormed and damaged by freedom fighters in May 1848 . The emergence of less susceptible, faster and more powerful processes heralded the departure from optical telegraphy.
From 1833 Wilhelm Weber , Carl Friedrich Gauß and Carl August von Steinheil experimented with electromechanical telegraph technology. Inspired by this, the Prussian telegraph director O'Etzel carried out his first - initially private - experiments with the Steinheil telegraph from 1837 onwards. In the same year the five-needle telegraph was put into operation by William Fothergill Cooke and Charles Wheatstone on the North Western Railway near London.
The first longer test track approved by the government was built in Prussia in 1846. A double wire connection was installed above ground along the railway line from Berlin to Potsdam. O'Etzel chaired the commission responsible for making experiments with electromechanical telegraphs . On an experimental basis, he switched the electromechanical system into the line of the optical telegraph. Until 1848, the available telegraphic devices, the Morse writing telegraph and the pointer telegraph by August Kramer and Werner von Siemens , were also tested in the experiments . The competition announced by the commission was won by the pointer telegraph, which was used in 1849 on the newly built electromechanical telegraph lines between Berlin and Frankfurt am Main as well as between Berlin and Cologne. The latter line used the test setup to Potsdam and then ran underground to Cologne. When it opened on June 1, 1849, the operation of the optical telegraph on the same route was discontinued. The electromechanical telegraph was initially expanded from Cologne to Aachen; this route was completed by August 1849. On the other hand, optical telegraphy was operated between Cologne and Koblenz until 1852. On October 12, 1852, the electromechanical telegraph also began operating on this route and replaced the last section of the Prussian optical telegraph.
The stations were mostly sold after the closure of the telegraph line. Many are no longer there today due to demolition, fire or war damage, others have been converted into houses or restaurants. A half-timbered building the station 33 from Altenbeken was to another location translocated . In some places only street names like “Am Telegraphen” or “Große Telegraphenstrasse” are reminiscent of the former telegraph stations.
Today not a single station is completely preserved in its original state, there is no original signaling system. Some stations and masts were recreated, often only symbolically. In Straßenhaus, for example, there is a simple 1: 1 model of the former telegraph station with a symbolic pointer system - the municipality notably bears a stylized telegraph station in its coat of arms. In Iserlohn , too , the mast of station 43 was rebuilt with a pointer system. Historically and technically more or less demanding reconstructions and restorations of telegraph stations are available in:
- On the Telegraphenberg in Potsdam, location of station 4, the "Interest Group for Optical Telegraph 4" built a replica of the former signaling system in the form of a free-standing mast with indicators that can be adjusted from the ground.
- At the former station 7 on the summit of Marienberg / Brandenburg , on March 31, 2015, on the occasion of the 2015 Federal Horticultural Show, the replica of the previous signal system was installed on a raised tank from Brandenburger Wasser- und Abwasser GmbH.
- In 2011, near the former station 11 in Ziegelsdorf , a dummy telegraph with a nine-meter-high, functional mast was installed. There are also information boards about the telegraph line, and the Grabow Heimatverein offers guided tours by arrangement.
- Neuwegersleben in Börde - The out of dry stone built station 18 had been to ruin fall - there were only the foundation walls. It was rebuilt based on the original, equipped with a reconstructed signal mast and furnished in a contemporary way. The station can include a museum and has coordinates .
- Station 30 on the Hungerberg near Vörden (Marienmünster) was demolished in the mid-19th century; The Marienkapelle, consecrated in 1852, was built on its foundation walls. In May 2008, a modern observation tower was built about 30 meters from the station's original location . The 26 meter high construction made of larch wood carries a symbolic signal system mast in the "H" position for Hungerberg.
- Also in Entrup (Nieheim) in April 2012 a lookout tower with a telegraph attachment was built on the 231 meter high Lattberg in place of the no longer existing station 31. The aim is to create an optical connection between the observation tower at station 30 (Vörden / Huingerberg) and the reconstructed station 32.
- Oeynhausen - Station 32 was reconstructed on the old foundation walls on the initiative of the Oeynhausen Heimatverein in 1983–1984. It can be visited and has the coordinates: .
- Köln-Flittard - Station 50 was reconstructed in the 1960s. In the original it had a four-story tower integrated into a residential building. After the telegraph line was abandoned, this was demolished by two floors. The building fell into severe disrepair, especially after the Second World War. Between 1964 and 1971 it was restored by the City of Cologne with the support of the Chamber of Industry and Commerce and equipped with a reconstructed signal mast made by the training workshop of a Cologne Federal Railway Repair Shop. The observation room was furnished in a contemporary way, with dummies being used instead of the telescopes for cost reasons, and the stove, which is essential for operation in winter, was omitted. During the reconstruction, only one of the removed floors was rebuilt, so that the system does not reach its original height. The construction of the signal system comes close to the original, whereby the zero position of the indicators is incorrectly designed to be standing instead of hanging on the mast. The station was operated under the care of the Cologne City Museum as a branch and "Cologne's smallest museum". The family who lived in the residential building on a long lease took over the supervision on site. The branch office was closed in 2005 for cost reasons, and the telegraph station is only open to the public at irregular intervals, for example on the occasion of the Open Monument Day . After the closure, the city museum cleared out the museum-like observation room. The former leaseholder, who is now the owner of the building, completely overhauled the mast and signaling system and made them passable in 2006. The telegraph station with the coordinates is now part of the Stammheim - Flittard - Kunstfeld cultural path and has a corresponding plaque.
Contemporary representations in art, display boards, functional models, multimedia representations and original components of the telegraph are now exhibited in several museums: The Börde Museum Burg Ummendorf is home to the original indicator of station 16 (Ampfurth Palace) and the special exhibition “Winged words across den Bördekreis ”from February 1 to March 11, 2007 was dedicated to the telegraph. The German Museum of Technology Berlin , the Museum for Communication Frankfurt and the Museum for Communication Berlin also deal with the Prussian optical telegraph. The Berlin Communication Museum is exhibiting an original indicator, the origin of which is not known. The Pistor telescope at Station 45 near Breckerfeld can be viewed in Frankfurt , the only surviving specimen of its kind.
In autumn 2012 the book Preussens Telegraphenlinie Berlin – Koblenz, Telegraphenbuch III , edited by Manfred Menning and Andreas Hendrich, was published with a list of all 62 stations that was precisely researched and localized for the first time . In the foreword, Menning referred to the fundamental works by Herbarth (1978) and Beyer & Matthis (1995) as "Telegraph Books " I and II.
The “dictionary for telegraphist correspondence” and the instruction books for operating the system were completely redesigned by Wilfried Hahn in Fraktur and Arial script.
Telegraph Cycle Route
In 2016 a nationwide active association Optische Telegraphie in Preußen e. V. founded, which tries to make the former stations of the optical telegraph known again. For this purpose, a “telegraph cycle path” is to be set up along the former telegraph line through the federal states. A signposted route with uniform symbols is being developed for this. With the inclusion of sights along the route, the cycle path is intended to create a “cultural link across Germany”. The project is supported by the development program for rural areas of the state of Saxony-Anhalt 2014-2020 (RDP) according to the measure "Support for local development LEADER (CLLD)" from funds from the European Agricultural Fund for Rural Development (EAFRD) and State of Saxony-Anhalt supported. The signage in Saxony-Anhalt has already started.
- Optical telegraph line Metz – Mainz
- List of stations of the Prussian optical telegraph
- Hamburg optical telegraph
- Dieter Herbarth: The development of optical telegraphy in Prussia. Cologne 1978, ISBN 3-7927-0247-9 .
- Hermann Kellenbenz : The historical importance of the telegraph station in Cologne-Flittard. In: Rheinisch-Westfälisches Wirtschaftsarchiv zu Cologne: The telegraph station Cologne-Flittard. A little history of communications engineering . Cologne 1973, pp. 9-20, ISBN 3-933025-19-2 .
- Klaus Beyrer and Birgit-Susann Mathis (eds.): As far as the eye can see: the history of optical telegraphy. (Publication by the Museum for Post and Communication , Frankfurt am Main, on the occasion of the exhibition of the same name from April 27 to July 30, 1995), ISBN 3-7650-8150-7 .
- Manfred Menning, Andreas Hendrich (Ed.): Prussia's Telegraphenlinie Berlin – Koblenz and contributions to the history and geology of the Potsdam Telegraphenberg and its surroundings / Telegraphenbuch III. Potsdam 2012, ISBN 978-3-00-039730-1
- Hans Pieper: From the history of communications technology from antiquity to the present - with special consideration of optical telegraphy in France and Prussia. In: Rheinisch-Westfälisches Wirtschaftsarchiv zu Cologne: The telegraph station Cologne-Flittard. A little history of communications engineering . Cologne 1973, pp. 21–58, ISBN 3-933025-19-2 .
- Karl-Heinz Göttert : Attack on the telegraph. Historical detective novel. Cologne 2004, ISBN 3-89705-336-5 .
- Jürgen Bräunlein: The optical telegraph line Berlin - Koblenz. From a pioneering act to a cultural monument . Das Archiv , Issue 1, 2012, pp. 6–11, .
- On the history of Telegrafenberg Potsdam ( Memento from May 22, 2009 in the Internet Archive )
- Optical telegraph in Prussia - Station 4 (Telegrafenberg Potsdam) with information about optical telegraphy, the Telegrafenberg in Potsdam and its surroundings and many of the 62 stations
- Optischertelegraph23.de - information about the line
- OpenStreetMap themed map with layers of telegraphs
References and comments
- Dieter Herbarth: The development of optical telegraphy in Prussia . P. 19 ff.
- Herbarth, p. 37
- Herbarth, p. 41 f.
- Herbarth, p. 44
- Hermann Kellenbenz: The historical significance of the telegraph station in Cologne-Flittard . P. 13
- Kellenbenz, p. 49; Herbarth, p. 49
- Manfred Menning, P. Fuchs, A. Schwarz, Andreas Hendrich, P Sukkau: Prussia's opto-mechanical telegraph line Berlin - Cologne - Koblenz 1832-1852 . In: Manfred Menning and Andreas Hendrich (eds.): Preussens Telegraphenlinie Berlin-Koblenz; Telegraph Book III . Potsdam 2012, ISBN 978-3-00-039730-1 , pp. 6 .
- Hans Pieper: From the history of communications technology from antiquity to the present , pp. 43–44
- Herbarth, p. 48
- M. Menning & A. Hendrich, Telegraphenbuch III, p. 28
- Herbarth, p. 110
- Herbarth, p. 51
- Herbarth, p. 53
- Birgit Susann Matthis: Everyday life of the telegraphist . In: Birgit Susann Matthis and Klaus Beyrer (eds.): As far as the eye can see: the history of optical telegraphy . Braun, Karlsruhe 1995, ISBN 3-7650-8150-7 , pp. 200 .
- Herbarth, p. 60
- Matthis, p. 196
- Menning, Fuchs, Schwarz, Hendrich; Pp. 8-10
- Herbarth, pp. 63-163
- Optical telegraphy in Prussia. Retrieved November 28, 2019 .
- Wilfried Hahn: Optical Telegraph 23 - History. Retrieved September 1, 2019 (German).
- Herbarth, pp. 54–55
- Herbarth, pp. 54-55; Chapter 3 of the Telegraph's Instruction
- Herbarth, pp. 56, 60
- Herbarth, p. 56
- Pieper, pp. 50–52
- Herbarth, p. 63
- Telegraph Corps of the Prussian Optical Telegraph: Instructions book for telegraphists . provided by Wilfried Hahn. tape 2 , p. 61-64 .
- Herbarth, pp. 59-60
- Kellenbenz, p. 14
- Herbarth, p. 118
- Herbarth, p. 168
- quoted from Pieper, p. 50
- Pieper, p. 52
- Pieper, p. 59
- O 'Etzel: Memoire on telegraphy in France, quoted in Herbarth, p. 61
- All information from Herbarth, p. 61
- Optical telegraphy in Prussia. Retrieved November 1, 2019 .
- Pieper, p. 59 f.
- Herbarth, p. 62
- Herbarth, pp. 46-47
- Mathis, p. 195
- § 2 of the Instructions Book for Telegraphists, Volume 1: Characteristics of a good telegraph officer
- Herbarth, p. 117
- Herbarth, p. 116
- Website for station 43 at www.optischertelegraph4.de, accessed July 10, 2008 
- Karl-Heinz Rumpf: Drumming Telephones Transistors, VEB Verlag Technik Berlin 1971, pages 167 and 17
- Herbarth, p. 121
- The course of the Great Telegraphenstrasse in Cologne, which was laid out in 1839, pointed to the signal system on the tower of St. Pantaleon, which was clearly visible from the street. There is also a "Small Telegraph Street"
- "IG4" website , accessed on July 2, 2009
- Station description for station 7 on optischertelegraph4.de, online , accessed on April 2, 2015
- Mitteldeutsche Zeitung on April 13, 2012, online , accessed on April 14, 2012
- Website of the Bördekreis. Archived from the original on May 5, 2005 ; Retrieved January 7, 2007 .
- Information on station 30 at http://www.optischertelegraph4.de/ , online , accessed on April 25, 2012
- The tower roof floats in: nw-news.de from April 25, 2012, online , accessed on April 25, 2012
- Website of the Teutoburg Forest / Eggegebirge Nature Park. (No longer available online.) Archived from the original on May 22, 2009 ; Retrieved January 7, 2007 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- Herbarth, pp. 136-137
- The monument catalog of the city of Cologne only shows the current, three-story building condition after restoration. In addition to the description by Herbarth (p. 136–137), the statements on the type-identical Station 49 in Leverkusen-Schlebusch show a four-story tower, for example by Rolf Müller: Optical telegraphy 1834–1849 Schlebusch station . - Brochure for the traveling exhibition; Stadtgeschichtliche Vereinigung e. V. (Ed .; text and images R. Müller), 1991, Leverkusen; Illustration of the Leverkusen station of the same type; further information from Hans Metzmacher - info text in www.bilderbuch-koeln.de , accessed on August 28, 2011
- Bad news for the tenant - council votes for the closure of the listed telegraph. In: Kölner Stadtanzeiger, March 31, 2005
- Manfred Menning, Andreas Hendrich (eds.): Preussens Telegraphenlinie Berlin – Koblenz and contributions to the history and geology of the Potsdam Telegraphenberg and its surroundings / Telegraphenbuch III ; Potsdam 2012, ISBN 978-3-00-039730-1 , p. 5
- Telegraphenradweg Berlin - Koblenz. Retrieved May 28, 2018 .
- An ambitious project: The Telegraphenradweg . In: MOZ.de . ( moz.de [accessed on May 28, 2018]).
- Sabine Spohr: Cycle paths in Saxony-Anhalt, long-distance cycle paths, round trips: Telegraph cycle path. Retrieved May 28, 2018 .