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Heath Robinson
TUNNY codebreaking machine - this page is a stub

Heath Robinson was an electronic machine that was used as an aid in breaking the German Lorenz SZ-40/42 cipher machine during WWII. It was designed by Tommy Flowers and Frank Morrell of the General Post Office (GPO) research stations at Dollis Hill (north-west London).

It was the first machine produced by Tommy Flowers and his team after he was introduced to codebreaker Max Newman at Bletchley Park by fellow codebreaker/mathematician Alan Turing.

The machine is equipped with two tape readers, one of which is used for generating the wheel sequences of the Lorenz SZ-40/42 machine.

In recent years, the Heath Robinson has been rebuilt by a team of volunteers, and is now on public display at The national Museum of Computing (TNMOC) at Bletchley Park (UK).
The double tape reader for the Heath Robinson machine

The machine was named after Heath Robinson, a World War I cartoonist and illustrator who was known for his drawings of fantastic but ridiculously complex machines that were used for simple tasks, pretty my like Rube Goldberg did in the US [3]. As a result, the term Heath Robinson, or Heath Robinson Contraption was induced in the English language. In US English, such a design is often called a Rube Goldberg machine.

The double tape reader for the Heath Robinson machine Heath Robinson detail Volunteer Kevin Coleman standing in front of TUNNY, explaining Heath Robinson TUNNY plug panel
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The double tape reader for the Heath Robinson machine
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Heath Robinson detail
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Volunteer Kevin Coleman standing in front of TUNNY, explaining Heath Robinson
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TUNNY plug panel

Development of the Heath Robinson started in January 1943 and the first prototype was delivered at Bletchley Park in June 1943. It was put to work soon afterwards. At the heart of the machine is an electronic valve-based circuit, designed by Tommy Flowers, that performs the boolean XOR function (Modulo-2 addition) on a digital 5-bit teleprinter signal (as in the Vernam cipher).

One paper tape reader is loaded with the cipher text that had to be at least 2000 characters long. The other reader was loaded with a tape that contained the possible Chi-wheel start patterns of the Lorenz. It had to be exactly one character longer than the cipher text tape, so that it would be displaced by one character on each pass.

The tapes were read at 1000 characters per second. It was vitally important to keep the two tapes 'in sync' with each other, but this appeared to be difficult in practice due to tape stretching. Several mechanical solutions were tested and applied to solve this tape synchronisation problem.

After several improvements, the Heath Robinson eventually led to the development of Colossus, the first electronic programmable computer, which was also used to break the Lorenz cipher. Colossus did not suffer from the synchronisation problem as it used only one tape reader, whilst the Chi-wheel start patterns were generated internally by Colossus, using the spocket hole to synchronise the machine. Nevertheless, the Heath Robinson remained in service as it appeared to be usefull for some dedicated tasks. Several design variants and 'specials' were derived from it.

  1. Wikipedia, Heath Robinson (codebreaking machine)
    Retrieved January 2014.

  2. Tony Sale, The Rebuild of Heath Robinson
    2001. Retrieved January 2014.

  3. Wikipedia, W. Heath Robinson
    Retrieved January 2014.
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Crypto Museum. Created: Saturday 11 January 2014. Last changed: Saturday, 24 February 2018 - 11:51 CET.
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