The wheel patterns are the settngs of the small switches (cams) around each of the Lorenz SZ wheels. These were initially only changed monthly, but later on in the war, the motor wheel patterns would be changed daily. From August 1944, all wheel patterns were being changed daily.
Cribs used on Dragon
What is a crib?
A crib is an educated guess at a piece of plaintext which could be within the enciphered message. This was the word that was to searched for within the de-chi. A list of common words (some with teleprinter codes) which could be searched was built up over time, a different list for each of the Lorenz links and even per direction (some are based on how a specific operator at each end typed spaces or shift codes). A few examples are selectable below.
Select a button to set the crib directly or type in the actual crib letters you want to search for.
Set my crib:
(Secret plus a space ) - Try on Tape 1
(Shift to letters[x2] Roem (Roman numerals) space  Shift to numbers[x2]) - Try on Tape 2
Try on Tape 3, multiple times
Gurnard (Berlin end)
Jellyfish (Berlin end)
Choosing a De-Chi tape
The input for the Dragon is a pre-prepared De-Chi paper tape. The De-Chi is the ciphered message with the key generated from the Chi wheels for that message removed. The settings for the De-Chi were generally calculated by Colossus first and the tape created on other machines. This was then inserted into the TeleType reader on Dragon at the first character position.
Click the view deciphered text buttons to see the completely deciphered text so you can see if you have found a match within the text correctly. Don't forget, Dragon searches within the ITA2 message, but there is the decoded text version if you wish to see the full message.
De-chi result from Dragon - FAO: The Testery .. URGENT
No result found yet
Counter display (built by the British as an addition to the American Dragon) showing the current position of the de-chi tape being read in. The Dragon has stopped here as it has found a possible match on the PSI wheels at the 202nd character.
The current 10 characters currently under examination shown in ITA2 code. This is currently showing that the stopped position was reading the de-chi characters AZMZAFIMIV
The strip of lights on each rack shows the matching PSI wheel positions which have matched the crib being tested. There is one set for each of the 5 PSI wheels. This one is showing that the contracted crib + de-chi being tested (TGE4UM8) has matched PSI wheel 5 between position 54 - 59