In the classical version a central ignition coil generates the high voltage necessary for the ignition of the fuel-air mixture.
A mechanical ignition distributor ensures that this voltage reaches the individual cylinders and spark plugs successively - and at the right time.
For this purpose, the ignition voltage is led through a distributor cap and the ignition cable is led to the spark plug connection. From here it reaches the end of the middle electrode and overcomes the air gap to the earth electrode in the form of a spark.
In the more modern version a pencil coil is used for each spark plug - the so-called fully-electronic ignition with static ignition distribution - neither mechanical ignition distributors nor high-voltage ignition cables are required.