I am doing research on the Bombe Machine, and I read that when the Bombe tries to find the stecker (plugboard) partners of letters, it only needs to use the rotor types and arrangement and also the "rotor core offset," which is just a combination of the rotor positions and the ring settings.

However, the ring setting does matter. If the 1st rotor position is A and the ring setting is A, the core offset would be the same as if the rotor position was B and the ring setting was B, but the 1st rotor output would be shifted down a letter, which would produce a drastically different output.

So, how do they account for that? I don't see how neglecting the ring setting is fine.


1 Answer 1


I didn't want to delete this question, but it seems like after pondering this for a week I finally understand right when I seek help online. When the ring setting and the rotor position all increase by the same amount, they cancel and so the ring pretty much stays the same. Although the contact points of the ring to the alphabet ring is different, it makes no difference, since it's not the contact on the alphabet ring that matters but instead the contact of the pin with respect to the next rotor.

  • 1
    $\begingroup$ I have the same observation: asking a question is a good way to reformulate it, and find the answer shortly afterwards. I wonder if putting it online helps, or if it would be enough to wait say 24h before clicking "post our question" for real (saving the question and title locally just in case, even though one pending question is supposed to be saved on the server for a while). $\endgroup$
    – fgrieu
    Commented Jun 13, 2020 at 9:29
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    $\begingroup$ There is a term called "rubber ducking" where you ask somebody just to find the answer yourself that captures above. We generally like you asking the question anyway, as you can answer it yourself too, and that may be really helpful to others. So I'm a happy rubber duck now I suppose (never seen a "ugly, unhappy rubber ducky by the way"). $\endgroup$
    – Maarten Bodewes
    Commented Jun 13, 2020 at 14:15

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