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Ignition systems based upon the concept of the generation of measured and timed electrical impulses have existed since the early 1900s. Modern day electronic ignition no longer requires as many electro-mechanical parts in the system, the key one being the distributor. It is built upon a solid state circuit of sensors that trigger a switch, which passes current through the ignition coil. These regularly passed electrical impulses travel to spark plugs that then ignite the fuel. Such an electronic system is more efficient and can support higher engine horsepower levels than older distributor or mechanically-controlled systems.
The primary advantage offered by an electronic ignition that is circuit-based instead of mechanically-controlled is in how the electrical impulse is distributed to the spark plugs. Utilizing transistors, sensors, and electrical switches, such as the thyristor, to control electrical flow is more accurate, reliable, and durable than a breaker-point system controlled by a mechanically-rotating distributor head. Since it is highly precise, this also prevents incomplete combustion of fuel in the piston chamber of an engine, leading to better fuel efficiency and reducing pollution.
An electronic ignition also automates several of the processes of ignition control that had to be manually adjusted or set in the past. Early magneto systems required hand-cranking instead of an electric start, and these were first replaced by non-rechargeable dry cell batteries that had a limited life span. Earlier systems were also limited by the amount of voltage they could generate, and such systems had imprecise timing of the distribution of electrical current overall. This kept early automotive vehicles operating at lower speeds and consuming more fuel than is the case with a newer electronic ignition.
Automotive, boat, and other large gasoline, kerosene, or diesel engines usually have an electronic ignition. Aircraft differ in that they often lack an alternator and still utilize magnetos, as they can generate their own electrical power. Smaller gasoline-based engines with spark plugs but no built-in batteries, such as lawnmowers, chainsaws, and leaf blowers, also utilize magnetos.
Cars built prior to the mid 1970s that utilized a distributor-controlled electronic ignition can also be retrofitted with newer technology which combines the ignition system to the fuel injection system as one more efficient unit. Where such retrofitting is not possible on a particular model, kits exist for upgrading a classic distributor-controlled vehicle without fuel injection to electronic ignition.