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| | Enigma machine - Wikipedia, the free encyclopedia |
 | | A third version, Umkehrwalze C was used briefly in 1940, possibly in error, and was solved by Hut 6 |
 | | The fourth version, first observed on 2 January 1944 is a rewireable reflector, called Umkehrwalze D, allowing the Enigma operator to alter the connections as part of the key settings. |
 | | into the machine, twice, to allow for detecting transmission errors. |
| en.wikipedia.org /wiki/Enigma_machine (6155 words) |
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