What is the Prussian optical Telegraph?
The Prussian optical semaphore was a telegraphic communication system that operated from 1832 to 1849, capable of sending messages between Berlin and the Rhine Province using optical signals over a distance of 588 kilometers.
The semaphore line consisted of up to 62 semaphore stations, each equipped with signal masts. These masts had six semaphore arms attached, which could be operated using ropes.
The stations were equipped with telescopes, allowing telegraphists to read specially coded information from a signaling station and immediately pass it on to the next station.
Three telegraph expedition offices in Berlin, Cologne, and Koblenz managed the reception, encoding, decoding, and dispatch of state dispatches.
Read more about the Prussian optical semaphore on Wikipedia (de)
Encoding of characters, syllables, words, sentences
With six semaphore arms that could assume angles of 0° (rest position, hanging from the mast), 45°, 90°, and 135°, it was theoretically possible to represent 4096 characters. However, the rest position of the entire semaphore did not represent a separate character. O’Etzel’s code system used the arm positions as code numbers from 0 to 999, as well as combinations of two digits (separated by a dot).
The coding method is derived from two pointers that rotate clockwise. With one of the arms of an indicator pair in the default position, the second indicator could assume four positions (1, 2, 3, 0 or 0, 4, 5, 6). In this way, a single indicator could represent code digits 0 to 6. Representation of digits 7 to 9 was achieved by combining two arms, with the left arm remaining in position 6 and the right arm showing 1, 2, or 3.
In addition, there were combinations of two indicators, where the right arm signaled 1, 2, or 3 while the left arm was positioned to represent 4 or 5. Such combined symbols were read as double digits and written with a dot separating them, for example, “4.1” or “5.3.”
For setting and reading, the three levels were labeled A, B, and C, with readings going from bottom to top. The notation for a complete symbol position was A [bottom level] B [middle level] C [top level], for example, “A5.3 B7 C4.3” – in this example, the middle semaphore arms represent the code digit 7, while the top and bottom each form a combination (double digits). Each level of the signal mast represented a digit or double digit of the code number with its indicator position.
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The function of the Prussian optical telegraph (Germany/Prussia)
At the top of the screen is a slider where you can choose between Encrypt and Decrypt.
Encrypt
When you select ‘Encrypt’, a text field appears where you can enter the text you want to encrypt. Below Display Result, the encrypted text appears as a graphical representation, and the code points are shown underneath.
Decrypt
When you select ‘Decrypt’, a slider appears with options for Text Mode and Visual Mode.
Text Mode
When you select ‘Text Mode’, a text field appears where you can enter the text that needs to be decrypted. In the Text section, the decrypted text appears, and under Display Result, the graphical representation is shown.
Visual Mode
When you select ‘Visual Mode’, an image of a symbol appears with all characters in gray. You can tap on a part of the symbol to turn that part red, and tap again to remove the red. The red parts together form one number or letter. The following buttons affect the output of the symbol:
Starts a new symbol
Removes the last symbol
Removes all symbols
In the Text section, the decrypted text appears, and under Display Result, the graphical representation is shown.
