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Tunny machine jack board
The white pegs on the Tunny machine jack-board define the wheel pattern, and they could be set to an on or off position to represent the position of the Lorenz rotors.
In the 1940s, the Metropolitan Police came across odd radio messages while monitoring transmissions in the hunt for spies. The British worked out they had been encrypted using teleprinters, according to Whetter.
On August 30, 1941, the British intercepted two test messages on new German radio links that had the same characters. The first message had 4,000 characters, while the second had 3,900 characters. John Tiltman, the head cryptanalyst at Bletchley, decrypted the message, and worked out the 4,000 characters were in cipher text and the 3,900 in cleartext.
Tiltman passed the messages to William Tutte and his team, who deduced the Lorenz machine structure and its operation. They worked out how the rotors interacted with each other, and with other complex matrices, using pencils and paper.
Tutte passed these findings to the Post Office research station at Dollis Hill, where engineers built a machine to emulate the logical structure devised by the team— the Tunny machine. The engineers built the machine mainly out of telephone exchange components.
Photo credit: Bletchley Park
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