Virtual Wartime Bletchley Park
by Tony Sale

Menus with Single and Double Inputs with Subsidiary

This menu is shown in Fig 20 in the Report. Using setup text file brfig20.txt and starting wheel order 352, brings up the 3rd entry in the checking sheet in Fig 21. This is quite a good stop, 3 self-steckers, one confirmation but two contradictions on V and Y.

I leave it to the reader to verify the other stops. (that's code for saying I couldn't easily make them work!).

Same with menu in Fig 22, couldn't get the stops shown in the Checker sheet in fig 23.

The Bombe Test Menus.

Menu I. This is a very strong menu which only gives one stop for all wheel orders for 5 wheels. When I obtained the US Bombe Report from NARA this was the first menu used to test Bombe simulators and it immediately revealed the problem with the Bombe readout which I have described previously.

You can verify the single stop but I have set the setup text in brmenu1.txt to cover wheel order 312 to 325. The stop comes up at w/o 324 stop BUO Stecker letter 'L'. You can use the Checking Machine to verify the other Steckers.

Menu II. This menu cannot be run on this Bombe simulator because the menu requires 3 letters of offset. Normally only two letters are required, the first letter, not included, is assumed to be 'Z'.

Menu III. The setup data text file brmenu3.txt is set to just run w/o 153 and it brings up the second stop in the list, stop CBW stecker letter 'U'.

I have not yet managed to bring up the other stops listed.

Menu IV. This requires setup data file brmenu4.txt and just searches wheel order 243. It requires the machine gun to be switched off since the given stop LFT, has contradictions, i.e. two registers containing the same stecker letter.

Menu IVA. This uses setup data file brmenu4a.txt and just wheel order 243. The input is set to register E and current entry at 'A' which via the diagonal board puts current into register A position E.

A spurious stop comes up first then the three stops quoted in the Report.

Again, the machine gun needs to be off since the stops contain contradictions.

Menus V and VII. cannot be run because they requires three letter offsets.

Menu VI. is left as an exercise for those interested.

Conclusions.

I hope this exposition, incomplete though it is, has given the reader an insight into the workings of the Turing/Welchman Bombe and an understanding of menus, how they were run and how the results were achieved.

If you have found this interesting I suggest you try breaking some real messages which will shortly be going up on codesandciphers.

Tony Sale, March 2002.

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This page was originally created by the late Tony Sale
the original curator of the Bletchley Park Museum

Virtual Wartime Bletchley Park by Tony Sale

Menus with Single and Double Inputs with Subsidiary

The Bombe Test Menus.

Conclusions.

Virtual Wartime Bletchley Park
by Tony Sale