The easiest way to understand the path of the current through the rotors is to
make up six tables for the three wheels, three going forward and three going
backwards plus a table for the reflector.
The simulator was used with rotors
III, II, I and
The simulator advances the rotor when the first key is pressed, i.e., the first entry.
To simplify, set the rings to
1, 1, 2.
Then when you press the the first key the rotor will have the fixed terminal
on the terminals from keyboard matching the letters on the core of the rotor (which contains the fixed wiring of the rotor).
The path is rotors
I-II-III, reflector, III, II, I.
The current path is
A-E,E-S,S-G then the reflector gives path
G-L, then using reverse tables starting at wheel
III, the return path is
L-F, F-W, W-N. The result of entering
A is the letter
For the next
A entered, the rotor shifts by one so that the letters on the rotor are shifted relative to the terminals from the keyboard (these are fixed).
A from keyboard goes to the
A terminal but now goes to letter
B on rotor. As before, using the tables,
B goes to letter
K on rotor but because of the shift goes to terminal
J of the next rotor (assuming no shifts of other rotors). Our current path is now
J-B, B-D, Reflector D-H, with return path (using reverse tables starting at rotor
H-D, D-C. Because of the shift of the rotor, the
C terminal is opposite the letter
D on the core of rotor
D on the rotor is wired to
G is opposite the terminal
of the shift. Thus the second
A will exit as an
The rotors used were (for first three letters on rotors )
ROTOR.I.... A-E,B-K,C-M ,.... THE RETURN IS.. A-U,B-W,C-Y ....
ROTOR.II.... A-A,B-J,C-D,.... THE RETURN IS.. A-A,B-J,C-P .....
ROTOR.III.... A-B,B-D,C-F...... THE RETURN IS.. A-T,B-A,C-G....
REFLECTOR (B)... A-Y,B-R,C-U..
The rotors have a ring on the left-hand side of the rotor which has the 26 letters
or numerals. This ring is spring-loaded and can be pulled outward so that
it can rotate relative to the main body (the core).
Beneath the ring is a dot on the main body which is fixed. This is usually
set to the
A position on the rotor. If we want to change the ring setting to
or position 2 then we can do this by pulling out the ring and holding the core
A position (relative to the fixed keyboard position
A), move the ring so that the letter
2) on the ring is opposite the dot on the core.
Then release the ring and now we have letter
B in the window instead of
The rotor must now be turned so that the letter
A on the ring shows in window.
A reverses the normal direction of rotor and the
Z position of the rotor is now opposite the fixed
.............D..C..B..A..Z..Y..X...........fixed terminals from keyboard .....
.............D..C..B..A..Z..Y..X...........core of rotor.......................
Now change to ring setting
Now rotate so that
A shows in the window of the rotor.
This rotates the lower two rows since the ring is engaged.
The dot at
A on the middle row which represents the core (where all the wiring is) is now in the
B position relative to terminals from the keyboard (top row). Note that the core now has
Z next to our
A terminal on top row.
The window on lower row shows as
If we now select a key on keyboard, then this will rotate the rotor so that
B will show in the window. The middle row will now have
A next to the
A terminal from the keyboard.
This is why you can set the rings to
1, 1, 2 on simulator so that we get a read out from the
A contact. The
2 setting is equivalent to the