Electronic Ignition: Operation

The reluctor rotating with the distributor shaft produces a voltage pulse in the magnetic pickup each time a spark plug should be fired. This pulse is transmitted through the pickup coil to the power switching transistor in the control unit and causes the transistor to interrupt the current flow through the primary circuit. This break in the primary circuit induces high voltage in the secondary circuit and fires a spark plug.

The length of time the switching transistor blocks current flow is determined by electronic circuitry in the control unit. This determines dwell. Dwell is not adjustable, changes are not necessary. The magnetic pickup and control unit have replaced the function of the contact points. These show no signs of wear and periodic checks of timing and dwell are not necessary.