A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current.
Hand-cranked magneto generators were used to provide ringing current in early telephone systems.
Magnetos adapted to produce pulses of high voltage are used in the ignition systems of some gasoline-powered internal combustion engines to provide power to the spark plugs. The magneto is now confined mainly to engines where there is no available electrical supply, for example in lawnmowers and chainsaws. It is also universally used in aviation piston engines even though an electrical supply is usually available. This is because a magneto ignition system is more reliable than an ignition coil system which relies on a battery.
Magnetos were rarely used for power generation, although they were for a few specialised uses.