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In the ignition system of a petrol-powered internal combustion engine, the distributor is a device which routes the spark to the correct cylinder. It consists of a rotating arm called the rotor arm which contacts the central high tension cable from the coil via a carbon brush. The rotor arm passes close to (but does not touch) the output contacts which connect via high tension cables to the spark plug of each cylinder. Within the distributor, the high voltage energy is able to jump the small gap from the rotor arm to the contact.

Modern engine designs are tending to do away with the distributor, preferring instead to have an integrated coil within each spark plug. This avoids the need to switch very high voltages, which is very often a source of trouble, especially in damp conditions.