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USSR
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T-205   Wecha
Telex encryption device - this page is a stub

T-205, codenamed Wecha (Russian: Веха), was an electromechanical rotor-based encryption & decryption device for telegraphy (telex) signals, introduced in 1964 by the USSR as the successor to the T-204 (Wolna). Like its predecessor, the T-205 had the size of a large wardrobe, and was built around multiple cipher mechanisms – or drums – with five rotors – or cipher wheels – each. In the former DDR (East Germany), the T-205 entered service in 1975/76 to replace the T-204. 1

Unlike with the T-204 however – where each rotor had to be removed individually – each drum of the T-205 (with five rotors installed) could be removed in one piece. This allowed new drums — set to a future key — to be prepared well in advance of a that key coming into effect. As soon as the new key came into effect (e.g. at midnight), the drums could be swapped in a few seconds.


As far as we know, there are no surviving examples of T-205 cipher machines on public display. The diagram above shows a single rotor cage, or drum, of which one cipher wheel appears to be missing. Each T-205 had two of these drums, located side-by-side. The one shown here is from the collection of Immo Hahn, who rescued it from a demolition site in 2009 [1]. A similar set, which all five rotors present, is shown in Klaus Schmeh's excellent book Codeknacker gegen Codemacher [2]. Further information and drawings can be found on Jörg Drobick's website [3].

  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.

Front view of the drum T-205 drum seen from the front left T-205 drum seen from the front right T-205 drum seen from the front Bottom/rear view Rotor set removed from the drum Rotor set removed from the drum Stepping levers
Stepping gear Hand crank Four wheels on a spindle (one wheel missing) Four wheels on a spindle (one wheel missing) Four wheels on a spindle (one wheel missing) Close-up of the rotors Right side One wheel removed from the spindle
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Front view of the drum
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T-205 drum seen from the front left
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T-205 drum seen from the front right
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T-205 drum seen from the front
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Bottom/rear view
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Rotor set removed from the drum
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Rotor set removed from the drum
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Stepping levers
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Stepping gear
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Hand crank
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Four wheels on a spindle (one wheel missing)
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Four wheels on a spindle (one wheel missing)
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Four wheels on a spindle (one wheel missing)
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Close-up of the rotors
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Right side
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One wheel removed from the spindle

Complete system
A complete T-209 cipher system consisted of three major parts that were each housed in a grey metal enclosure, with double hinged doors at the front, as illustrated by the diagram below. The total height is slightly more than 1 metre, which is about half the height of the T-204. At the top is the actual TC-29 (ТЦ-29) cipher machine. It has two rotor cages, or drums, with 5 rotors each: one set for transmission and one for reception. Each drum has its own character counter and an additional set of five smaller wheels that control the advancing of the cipher wheels in each cage.


At the center is the SU-205 (СУ-205) synchroniser. The case at the bottom contains the spare parts, or ZIP (Russian: ЗИП), which includes a complete rotor cage with five rotors, and spare sets of rotors (cipher wheels) and the smaller advancing wheels. For a full description of the module, please check this page [3].


References
  1. Immo Hahn, Partly complete T-205 drum
    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-205 M1 Wecha
    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 - 18:06 CET.
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