Virtual Wartime Bletchley Park
by Tony Sale

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A menu from the Report with no stop given

This menu is fig 12 on archive page 14, Report page 9 in the Report.

There are no clues as to the stop (if any), and it has no closures but a long chain.

Assuming a possible 8 wheel set, it took 1 1/2 hours to find a stop, and it is a very good stop with 5 self steckers and 2 confirmations. A further run of 3/4 hour showed that this was the only stop.

If you want to get feel for how long this takes you can start at wheel order 123 and go to 876 as I had to first time. Remember this is 60!! times faster than the real Bombe, but also that they could put 10 Bombes onto it each doing part of the whole set of wheel orders and even put the menu twice on one Bombe.

If you are feeling chicken you can run the setup data brfig12.txt as it is with a wheel start of 551. This will bring up the stop in about 5 minutes.

When the stop comes up you can take the Stecker given for 'Q' the input menu letter and work it through with the Checking Machine.

Or you can just go on to the next menu in the report.

A Menu that did not work

The menu in Fig 14 on Archive page 15, Report page 10, is bad news. The text gives the plugging for it in Fig 15 and the Checking Machine run in Fig 17. This run quotes the stop as w/o 543 stop HKF and stop Stecker letter as 'C'.

A run of the menu on the Bombe simulator gives no stops for all wheel orders for 5 wheels. (SPARROW is a German Army key). No stops for a full 8 wheel set of runs. (unlikely but had to be tried). Tried 'C' UKW, no stops.

Also taking the stop through the Checking Machine doesn't work.

So either there is a fault in the menu or just possibly the pluggable D UKW was used.

Left as an exercise for the reader!.

A Double Input Menu.

Next comes Fig 18, a double input menu. The Checking Machine runs for the resultant stops are shown in Fig 19. These give the first stop as w/o 231 stop MZK with Stecker letter B in the X register. There is also a note '-ZAO' which means with the Enigma drums between R and E disconnected.

Running the Bombe simulator with setup data from brfig18.txt brings up two stops for w/o 231 the second of which is the one shown on the checking sheet in fig 19. This is not a very good stop since P appears as Steckered to 3 letters. This stop would be rejected with the machine gun switched on. It is not clear why the R<->E link has to be removed, certainly if it is added to the menu no stops come up.

This is described as a double input menu and the text indicates two inputs, one to the X register on the main menu and the other to the A register on the secondary register. I have not put double inputs into the Bombe simulator, the same effect can be achieved via the diagonal board by choosing the input current letter to be the register letter on the secondary menu. (A in reg. X -> X in reg. A).

I leave it as an exercise for the reader to show the other stops on the checking sheet.

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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

A menu from the Report with no stop given

A Menu that did not work

A Double Input Menu.

Virtual Wartime Bletchley Park
by Tony Sale