Enigma - The Ring Setting

From: James Vanns (jimv_at_canterbury.ac.uk)
Date: 01/23/05 

Date: 23 Jan 2005 09:10:43 -0800

I have read much material on Enigma albeit material from the NET and
not books. This is my problem; I have read quite a few articles over
the past 6 months that I had googled for and unfortunately some seem to
contradict others or at least omit important details!

I am confused about the ring setting mainly. I was to understand that
each rotor (I-VIII) had a single notch (actually VI-VIII being an
exception as they had two) in a fixed position (according to _all_
rotor wiring descrptions I've found):

Wheel Wiring Notch Window

ETW ABCDEFGHIJKLMNOPQRSTUVWXYZ

I EKMFLGDQVZNTOWYHXUSPAIBRCJ Y Q
II AJDKSIRUXBLHWTMCQGZNPYFVOE M E
III BDFHJLCPRTXVZNYEIWGAKMUSQO D V
IV ESOVPZJAYQUIRHXLNFTGKDCMWB R J
V VZBRGITYUPSDNHLXAWMJQOFECK H Z
VI JPGVOUMFYQBENHZRDKASXLICTW H,U Z,M
VII NZJHGRCXMYSWBOUFAIVLPEKQDT H,U Z,M
VIII FKQHTLXOCBJSPDZRAMEWNIUYGV H,U Z,M

beta LEYJVCNIXWPBQMDRTAKZGFUHOS M4 only
gamma FSOKANUERHMBTIYCWLQPZXVGJD M4 only

An example: Rotor I has its notch at Y, II at M, III at D and so on.

So now I discover that the ring setting actually means these notches
are positionable. Is this true? If so whats the significance of the
above? Why associate Y with I if it's a variable? If indeed the ring
setting positions the notches relative to A-Z then when the ring
setting is set to 1,1,1 does this mean that the notch is at a, a and a?
Or does it refer to the above table - y, m and d?

So now this has also confused my understanding of the message key -
what exactly is that?

Can someone actually clear this up for me and avoid any further
confusion?

Regards

Jim