Twin or Dual Magnetos (plural) This applies to engines fitted with two independent magnetos and include some V twin engines where each cylinder's single spark plug is fired by it's own single cylinder magneto. Another example is the V16 engine where each bank of eight cylinders is fed by it's own eight cylinder magneto.

Dual Magneto Here the word 'dual' refers to the design where the HT comes from two independent sources.  Usually these HT sources are a conventional magneto and a battery/coil system. Sometimes, as in magnetos fitted to aircraft engines, both sources of HT are separate magnetos.

Dual Magnetos (plural) This is where two independent magnetos are fitted. Each cylinder has two spark plugs, each one being fired by a different independent magneto. This is the arrangement used with aircraft engines where duplication of the ignition system introduces a safety element. If one magneto fails, the other keeps the engine going - albeit with a slight drop in performance.

Dual Magneto (singular) As before, here the word 'dual' refers to the design where the source of the HT comes from two different sources. Magnetos of this type designed to be fitted to engines with two spark plugs per cylinder can be used with either or both of the HT sources at any one time. Again, usually these sources are a conventional magneto and a battery/coil system.

Twin Spark (also referred to as Dual , 2 or Two spark) Magneto In this arrangement, one magneto fitted with a specially wound coil allows both spark plugs in any one cylinder to be fired at exactly the same time. This synchronisation of the sparks provides a marked improvement over the other systems which use two independent ignition systems to fire the two plugs.

Dual 2 Spark Magneto This type of magneto combines the functions of both dual and twin spark magnetos in the one unit.