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USSR
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T-204   Wolna
Telex encryption device - this page is a stub

T-204, codenamed Wolna (Russian: Волна), was an electromechanical rotor-based encryption & decryption device for telegraphy (telex) signals, introduced by the USSR around 1962. The device had the size of a large wardrobe, and was built around drums with five rotors, or cipher wheels. In the former DDR (East Germany) the T-204 M was introduced in 1966, followed in 1969 by the T-204 M1. [3]. Following the Six-Day War 1 they were replaced by the T-205 from 1975 onwards.

As far as we know, there are no surviving examples of the T-204 machine on public display. The image below shows the cipher mechanism, or drum, as it was rescued by German collector Immo Hahn from a demolition site in 2009 [1]. Although the artefact has been damaged badly – and is clearly beyond repair – its features are still visible. It shows that two sets of five rotors each were used side-by-side. Like with the German Enigma cipher machine, each rotor set is held between two fixed contact discs. It is also clear that the rotors had 13 contact points at either side.

Demolished cuipher mechanism of the T-204. Courtesy Immo Hahn [1].

The rotors are driven by a complex cog-wheel driven gear, with a variety of pawls, notches, levers and actuating solenoids, which makes it likely that the machine featured irregular stepping of the rotors, and that the wheels could probably move in both directions, similar to (but more complex than) the Russian M-125 Fialka, in which the wheels move in opposite (but fixed) directions. In 1975, the T-204 (Wolna) was succeeded by the T-205 — codenamed Wecha (Russian: Веха).

  1. During Six-Day War (5-10 June 1967) between Israel and some Arab countries (Egypt, Jordan and Syria) an unknown number of Soviet cipher machines had been captured by the Israelis. It is believed that eventually it enabled them (possibly with help from the NSA) to break the Soviet ciphers, which is why many Soviet systems were either replaced or modified several years later.

Cipher wheels
The image below shows one of the original rotors of the T-204, which is all we currently have of this machine. The wheel is largely destroyed as part of the demilitarization procedure, but is still good enough to show its original purpose. Many thanks to Immo Hahn for providing this item [1].


A similar cipher wheel — probably from the same source — is shown in Klaus Schmeh's excellent book Codeknacker gegen Codemacher [2]. Further details, photographs and other information is available from Jörg Drobick's informative website Der SAS- und Chiffrierdienst (SCD) [3].

Demolished cipher mechanism Fixed contact disc Mechanism detail Right side of a T-204 cipher wheel Left side of a (partly demolished) T-204 cipher wheel Interior of a T-204 cipher wheel Interior of a T-204 cipher wheel Parts and contact pins of a (demolished) T-204 cipher wheel
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Demolished cipher mechanism
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Fixed contact disc
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Mechanism detail
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Right side of a T-204 cipher wheel
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Left side of a (partly demolished) T-204 cipher wheel
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Interior of a T-204 cipher wheel
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Interior of a T-204 cipher wheel
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Parts and contact pins of a (demolished) T-204 cipher wheel

References
  1. Immo Hahn, Partly demolished T-204 cipher wheel - THANKS !
    Crypto Museum, March 2009.

  2. Klaus Schmeh, Codeknacker gegen Codemacher
    ISBN 979-3-937137-89-6. 2008 (German). pp. 119—120.

  3. Jörg Drobick, T-204 M1 Wolna
    Website: Der SAS- und Chiffrierdienst (SCD) (German).
    Retrieved March 2019.
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Crypto Museum. Created: Sunday 24 March 2019. Last changed: Sunday, 24 March 2019 - 16:03 CET.
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