|Extracts from Turing’s notes on the Enigma Machine, c.1939-42|
|(Catalogue reference: HW 25/3)|
The particular order we have chosen is known as QWERTZU order.
The diagram shows the connections when the key Q is depressed and supposing that C1 is connected to C3 through the wheels
The only outlet for the positive of the battery is through the Q key to G hence to C3 and then through the E bulb. The result is that the E bulb lights. More generally we can say
If two contacts C, C’ of the Eintrittswalz are connected through the wheels then the result of enciphering the letter associated with C is the letter associated with C’.
Notice that if P is the result of enciphering G, then G is the result of enciphering P at the same place, also that the result of enciphering G can never be G.
On the wheels are rings or tyres carrying alphabets, and rotatable with respect to the rest of the wheel; more about this under ‘turnovers’. When the machine is being used three of the wheels are put in between the U.K.W. and the E.W. in some prescribed order. The way that the current might flow from the E.W. through the wheels and back is shown below