This article contains technical details about the rotors of the Enigma machine. Understanding the way the machine encrypts requires taking into account the current position of each rotor, the ring setting and its internal wiring. Physical design of rotors Rotor electrical view No letter can map to itself, a cryptographic weakness caused by the same wires being used for forwards and backwards legs. Rotor offset The effect of rotation on the rotors can be demonstrated with some examples. As an example, let us take rotor type I of Enigma I (see table below) without any ring setting offset. It can be seen that an is encoded as an , a encoded as a , and a is encoded as an . Notice that every letter is encoded into another. In the case of the reflectors, in this example Wide is taken (Reflector B in the table below) where an is returned as a and the is returned as an . Notice that the wirings are connected as a loop between two letters. When a rotor has stepped, the offset must be taken into account to know what the output is, and where it enters the next rotor. If for example rotor I is in the -position, an enters at the letter which is wired to the . Because of the offset this enters the next rotor in the position. With the rotors I, II and III (from left to right), wide , all ring settings in , and start position , typing will produce the encoded sequence . Ring setting The ring settings, or Ringstellung, are used to change the position of the internal wiring relative to the rotor. They do not change the notch or the alphabet ring on the exterior. Those are fixed to the rotor. Changing the ring setting will therefore change the positions of the wiring, relative to the turnover-point and start position. The ring setting will rotate the wiring. Where rotor I in the -position normally encodes an into an , with a ring setting offset -02 it will be encoded into As mentioned before these encodings only happen after the key is pressed and the rotor has turned. Tracing the signal on the rotors is therefore only possible if a key is pressed while the rotors were in the position . With the rotors I, II, III (from left to right), wide , all