Magnetos adapted to produce impulses of high voltage for spark plugs are used in the ignition systems of spark-ignition piston engines. Magnetos are used in piston aircraft engines for their reliability and simplicity, often in pairs. Motor sport vehicles such as motorcycles and snowmobiles may use magnetos because they are lighter in weight than an ignition system relying on a battery. Small internal combustion engines used for lawn mowers, chain saws, portable pumps and similar applications use magnetos for economy and weight reduction. Magnetos are not used in highway motor vehicles that have a cranking battery, which may need more ignition timing control than a magneto system can provide, though sophisticated solid state controllers are becoming more common.