Ebay horror ...

My original question was aimed at Richard.... Anyone who even considers scrapping an Enigma should be LARTed. And anyone who thinks you can get 'simple rotary switches' from one doesn't really understand how the machine was built. Close. AFAIK, the reflector came in pretty early on. I've once used an Enigma machine (at Bletchley Park, of course). I wasn't able take said machine apart, of course, but I did manage to deduce some bits of how I think they were built. Firstly let me assume there are 26 keys and light bulbs. That might be wrong, but it's a working figure. Each key is a chageover switch. The normally open contact of all the keys goes to one side of the battery. The normally closed contact to one side of a lamp. The other side of all the lamps goes to all the batteries. What this means (of course) is that if the common contacts of 2 of the keys are linked, pressing one key lights the bulb associated with the other and vice versa. This means the same setting can be used to encryt and decrypt a message -- it's self inverse. These connections between the common contacts of the keys are made by the rotors. There are 26 contacts in a circle fixed to the chassis of the machine (one contact to each key common contact, of course). The first rotor has 26 contacts on one side that make contact with the ones on the chasiss. These are wired (essentially at random although all machines were, of course, the same) to 26 contacts on the the other side of the first rotor. This is repeated for the other 2 rotors (with different wiring patterns). Finally, the last side of the third rotor makes contact with the reflector. This has 26 contacts on it which are wired together in 13 pairs. When a key is pressed a current (from the battery) flows : Through the N/O contact of that key to one of the contacts on the chassis. From there through a wire on the 1st rotor to a contact on the other side of that 1st rotor Ditto for the 2nd and 3rd rotors Then though one contact on the reflector, along one of the 13 wires in the reflector to another contact on the reflector. Then back along a different wire in the 3rd rotor Ditto along different wires in 2nd and 1st rotors To a contact on the chassis (which must be different from the first contact I mentioned) Then to the common terminal of another key (which is not pressed) To the N/C contact of the that key to a lamp And back to the battery. As you said, there's a mechanical linkage to step one of the rotors on one position after each key press. And a 'carry' linkage that moves the next rotor on one step after the first rotor has gone round once. And when the seocnd rotor had gone round once, the third rotor was advanced one position. Ah yes, the plugboard. It has 26 2 pin sockets, each polarised (different size pins IIRC). One size of pin goes to the N/C contact of the corresponding keyboard switch, the other plugboard pin goes to the lamp. There's a contact inside each socket that shorts the socket pins together if there's no patch lead inserted, The patch leads had a 2 pin plug on each end, with the connections crossed over (large pin at one end to small pin at the other). Inserting a patch lead between 2 of the sockets effectively crossed over the external connections associated with those 2 sockets There are 2 places that the patchboard might have been connected (I don't know which is correct). One is between the common contacts of the keyswitches and the chassis contacts for the rotors. The other is between the N/C contacts of the keys and the corresponding lamps. The latter position would allow the Enigma to encrypt a letter as itself (that's impossible without the plugboard since as soon as a key is pressed, the corresponding lamp is out of circuit). With the plugboard between the keys and the lamps it would be possible for the encrypted form of a character to go via the plugboard to the lamp for that (unencrypted) character. Since I believe that the fact that a letter was never encrypted as itself was one of the weaknesses that was used to crack Enigma, maybe the plugboard was in the the first position I mentioned. Actually, wired as I described, no matter how the rotors are wired, and how the reflector is wired, you must end up with a 1-1 self-inverse mapping between keys and lamps for a given rotor position. So, are my guesses anything close to correct? -tony