Paul, hughdogz.
Sorry, I just read my post and realised how vague it was. Rubish in, rubish out (Sorry, I don't mean that your responses are rubish, but that due to my rubish question, you had very little to respond with).
My setup is a L28 with the same CAS shown in the picture above but without the drilled sync hole. I.E. High res slits on outside perimeter, 6 equal width Low res slits on the inside perimeter.
The computer is a megasquirt (for now).
What my question should have been is.
How does any computer, know which cylinder my engine currently has at TDC from my CAS signal (Which on a CRO would look like 6 equal space and equal width square waves. I.E. A periodic square wave)?
What prompted me to ask this was the following:
1/ Z32 and RB Signal discs that I have seen have the different width slits. From these slits, I can see that a computer could measure the width of the disc as apposed to the width of the smaller high resolution slits and therefore determine which cylinder needs to currently fire.
2/ My Disc has the same width slits (Talking about the low res inside 6 slits) and no reference slit or hole, as Hughdogz has drilled.
Hopefully I have made sense that time.
Thanks for your input guys, greatly appreciated.