Waveform for crank sensor with hall sensor??

I'm trying to understand the waveform for a crank sensor with hall sensor and msssing tooth trigger wheel. I came across this in The MasterECU training manual and it doesn't make any sense to mee ..can any one explain why there is a wide gap, followed by a wide pulse instead of two missing pulses?

Not all hall sensors work like that, but basically some hall sensors will switch high early when the first tooth is moving towards the sensor. The important thing to understand is generally the ecu will only be set up to look at either only the falling edge or only the rising edge (not both). In your example the falling edge is the accurate one. If you look at the spacing of the falling edges they are nicely spaced and there is the correct two missing teeth gap.

i just spent 20 min writing a reply to find the perfect reply had already been written while I was thinking, cheers Adam yours had a picture so it was certainly better

Adam, Thanks, great explanation! the key point for me was understanding that it's edges not "pulses"