BTW - I didn't compare the systems to the PerTronix versions. So, although I don't have access to corporate secrets and schematics, nor have I used an oscilloscope to prove each one, I would say that based on their characteristics:
- The P-I is fixed dwell without current limiting (like points) and therefore uses a coil resistor.
- The P-II appears to use fixed dwell with current-limiting like the GM 4-pin, and therefore no coil resistor.
- The P-III appears to use calculating power for true dwell control, and uses some of that calculating power to also incorporate multi-spark, and determine RPM for rev-limiting. It therefore uses no coil resistor. However, due to it's ability to somewhat adapt to other coils than the one recommended, I believe it also uses current-limiting. Or, it's a lot smarter than we give it credit for.