triggering an HEI module

[Tedscj at aol.com]

Hi,
Has anyone tried to determine what type of signals will trigger an HEI module?
To be more specific with what I want to achieve:
I have a little foreign four banger with a really pitiful points ignition.  I 
was thinking of converting it to GM DIS as a first step towards full-blown 
GM-EFI.
The problem is that the only after-market conversions from points available 
for this car are to 'optical sensor' ignition, which will result in a square 
wave signal from 0v to 12v.  I know HEI modules (and DIS) are looking for a 
sine wave.
Does anyone know if a square wave will trigger the module?
Even MORE specific:
my idea is this: Crane makes a unit (the XR-700) that is optical.  Their 
generic kit comes with a bunch of 'shutter wheels, including one for a v12.  
That's 12 slots.  Add two slots in the appropriate places (with an 
exacto-knife), and you have the correct pattern to fire a DIS unit (4cyl or 
6cyl... they require the same timing sequence.) (the GM DIS needs 6 equally 
spaced trigger signals, plus one 10' after TDC, per crank rev.) (you would 
double that if you were to plane on running it off of the distributor, as I 
am.)  And for the time being, I would just keep the mechanical distributor 
advance, which would send that advanced signal to the DIS unit, thus keeping 
my stock timing.  Pretty neat, huh?
which leads to my second question.....
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