I posted a long and dull thread about CAS whilst trying to get my PFC to work.
As you turn the distributor, you should see the voltage jump from 0V to about 4-5V.
I can't remember the pin outs but on one of them about 2degs of turn gives a pulse (this is quite difficult but if you turn it quickly you'll get about 2ishV) where as on the other there is 4 pulses per rotation.
Could get all geeky on you but that's the basics