Ignition Coil: Description and Operation

A Darlington type of power stage is mounted next to the ignition coil. This power stage is used to switch the primary current in the ignition coil on and off in place of the Hall control unit.
The ignition control unit sends a voltage signal to the power stage to operate it. The power stage will then switch the ignition coil primary current to control the spark discharge from the ignition coil. In this manner the power stage operates like a solid state pair of ignition points.