Coil Voltage

or maybe he's just asking about the concept.

HEI includes a current limiter.
The other systems of the time, and GM's previous (points) system control the current by reducing the voltage. The more curent through the resistance, the more voltage drops. Chrysler's resistance is mounted such that at driving high speeds it cools more and slightly reduces resistance. That's concept anyway.

Chrysler goes over that here
Ignition System Analysis (Session 259) from the Master Technician's Service Conference