Ignition System: Description and Operation

The Bosch electronic ignition system consists of a control module, a breakerless distributor, a high output ignition coil, an ignition switch, and a battery.
The distributor contains a rotating trigger wheel and a stationary magnetic pick-up coil. Standard centrifugal and vacuum advance/retard mechanisms are used.
Inside the distributor, a trigger wheel turns with the distributor shaft. The trigger wheel has one lug for each cylinder. As the trigger wheel rotates past the pole of the magnetic pick-up coil, a magnetic field is created that continually builds and collapses. This produces a low voltage electrical signal. This electrical signal is passed to the control unit, which controls the dwell time and at the same time interrupts the ignition coils primary circuit. This induces the high secondary output voltage from the coil that fires the spark plugs.