雙語暢銷書《艾倫圖靈傳》第5章:解謎接力賽(19)
Obviously, the rotors had to be marked in some way on the outside so that the different positions could be identified.
However, here entered yet another element of complexity.
於是這又增加了它的複雜性。Each rotor was encircled by a ring bearing the 26 letters, so that with the ring fixed in position, each letter would label a rotor position.
每個轉盤都鑲着一圈金屬帶子，帶子上依次銘刻着26個字母，當帶子在轉盤上固定好之後，一個字母就代表着一個盤位。
(In fact, the letter would show through a window at the top of the machine.)
機器上方有小窗口，可以看到代表當前盤位的字母。However, the position of the ring, relative to the wirings, would be changed each day.
然而，字母與電線之間的對應關係是可以改變的。The wirings might be thought of as labelled by numbers from 1 to 26, and the position of the ring by the letters A to Z appearing in the window.
用數字1-26來表示電線，用窗口上顯示的A-Z來表示轉盤的位置，So a ring-setting would determine where the ring was to sit on the rotor, with perhaps the letter G on position 1, H on position 2, and so forth.
通過帶位設定注，就可以決定它們的對應關係，比如令字母G對應1號線，字母H對應2號線，等等。It would be part of the task of the cipher clerk to make the ring-settings, and thereafter he would use the letters on the ring to define the rotor-settings.
帶位設定是密碼操作員的工作，然後他可以用窗口上的字母來表示當前的盤位。From the cryptanalyst's point of view, this meant that even if it were openly announced that rotor-setting 'K' was being used, this would not give away what at Bletchley they would call the core-position—the actual physical position of the wiring.
從密碼分析的角度看，這意味着即使公開宣佈正在使用盤位K，也不會泄露布萊切利所說的核位模式，也就是電線的連接關係。This could only be deduced if the ring-setting were also known.
只有同時知道盤位和帶位時，才能推導出相應的核位。However, the analyst might know the relative core-positions; thus settings K and M would necessarily correspond to core-positions two places apart.
不過，如果分析員知道盤位，而且帶位是不變的，那麼他就可以得到一個相對核位。So it was known that if K were at position 9, then M would be at position 11.
比如說，假定K在9號線上，那麼M就一定在11號線上。
