Tunny code-breaker rebuilt at Bletchley Park

Tunny code-breaker rebuilt at Bletchley Park

Summary: Engineers at the National Museum of Computing at Bletchley Park have rebuilt the Tunny machine, a key device used in decoding German High Command messages during the Second World War

TOPICS: After Hours

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  • AR 88 shortwave radio receivers, the Tunny machine and the 'Heath Robinson'

    An exhibition showcasing the Tunny machine, which was used to break German codes in World War II, opened at the National Museum of Computing at Bletchley Park on Thursday.

    This picture from the new Tunny Gallery shows, from left, rebuilt AR 88 shortwave radio receivers used to intercept encoded German messages; the Tunny machine, which produced the final decrypts of enciphered communications of the German High Command; and the 'Heath Robinson' machine, a prototype of the Colossus that supplied Lorenz wheel settings as part of the decryption process.

    The Tunny machine took a team of three people three years to rebuild. At the end of the war, Tunny machines were broken up and the components recycled, while the original circuit diagrams were destroyed or hidden. The team had to piece together plans for the machine from odd pieces of circuit diagram that had been squirreled away by engineers, as well as from the recollections of some of the original builders, according to John Whetter, one of the team leaders for the Tunny rebuild project.

    "We are leaving [the Tunny machine] as a legacy and a tribute to those legends at Dollis Hill [Post Office Research Station] and Bletchley Park who never got the recognition they deserved," Whetter told ZDNet UK on Wednesday.

    Photo credit: Bletchley Park

    See more photos of Bletchley Park on ZDNet UK.

  • AR 88 radio receiver bank

    AR 88 machines were used at Y Station Knockholt on the South Downs to pick up German messages using massive rhombic aerial arrays, Whetter told ZDNet UK.

    The signals were demodulated and passed through a pen recorder, which produced a trace in a square wave format. Young women were employed to physically read the square wave format, a series of ones and zeros, and translate it into letters. They had to punch out teleprinter tape for each individual encoded letter.

    Teleprinter signals were then sent to Bletchley Park via landlines, where Heath Robinson, and then Colossus, worked out the rotor settings used by a Lorenz machine to encode the original message.

    Photo credit: Bletchley Park

    See more photos of Bletchley Park on ZDNet UK.

  • The Tunny machine

    The Tunny machine turned the encrypted message into cleartext.

    At the top of the machine were three banks of relay switches called 'uni selectors', which represented the 12 rotors of the Lorenz machine.

    Below the uni selectors was a plug jack-board, which was the control panel for the uni selectors. Lamps above the jacks light up depending on the settings of the rotors: setting one has one lamp, setting two has two, and so on up to 27, as Lorenz machines had 27 rotor settings per rotor.

    The original Tunny machine was built after some ingenious mathematical and logical deduction by a number of British people.

    Photo credit: Bletchley Park

    See ZDNet UK's gallery of Acorn computers at Bletchley Park.

Topic: After Hours

Tom Espiner

About Tom Espiner

Tom is a technology reporter for ZDNet.com. He covers the security beat, writing about everything from hacking and cybercrime to threats and mitigation. He also focuses on open source and emerging technologies, all the while trying to cut through greenwash.

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  • Anybody heard of Harry Beckhough!
  • As a memberf the 'Bletchley District Gazette' during the 1960's, and living behind the 'Manor House' I enquired of my then Editor [ Carl Moser ] what went on in that area during the WWII.
    and he said in all sincerity, 'You will be an old man before details are exposed'...and how right he was.!! But I had talked to someone who had worked in the Postal communications, and he said then, that without the engineering procedures in operation at that time, the Academics, could not have succeeded....Alan Turing....God rest your Soul.
    daniel johnson-88fb3
  • went to 'Bletchley Parl a few years ago, fantastic place - i feel a return is in order :)
  • Great pics , better than the ones I took. I agree with Will above , I had a lovely visit to Bletchley when I was on holiday in England and look forward to going back some day. It brought some dusty old history to life for me.