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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  • Switches to finesse the decryption

    Underneath the jack-board was a telegraph relay. The bank of switches was used to finesse the output of the machine. Occasionally the decryted messages would turn into gobbledegook, so the switches would be used to go back and restart the machine from a specific point, without having to decode parts of the message that had already been decoded.

    Below the relay, shielded by two grey boxes, were the matrix control relays for the circuitry. There were at least 120 relays that controlled the operation of the machine, Whetter said.

    The entire machine was rebuilt using spares from BT telephone exchanges that were remodelled in the 1980s. All of the engineers that worked on the rebuild were ex-BT employees and had contacts at other museums, and so could lay their hands on the components, Whetter added.

    Photo credit: Bletchley Park

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

  • The wiring at the back of the Tunny machine

    The back of the Tunny machine took two people 18 months' solid work to rewire.

    "That was an absolute bastard of a job," said Whetter. "It was a labour of love."

    Each of the uniselectors had 25 outputs, while each switch had over 120 connectors.

    Further details on how to visit the Tunny Gallery can be found at the National Museum of Computing's website.

    Photo credit: Bletchley Park

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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.