Scion xb Ignition system is a system for igniting a fuel-air mixture. It is best known in the field of internal combustion engines but also has other applications, e.g. in oil-fired and gas-fired boilers. The earliest internal combustion engines used a flame, or a heated tube, for ignition but these were quickly replaced by systems using an electric spark .

The output of a magneto depends on the speed of the engine, and xb therefore starting can be problematic. Some xb magnetos include an impulse system, which spins the magnet quickly at the proper moment, making easier starting at slow cranking speeds. Some engines, such as aircraft but also the Ford Model T, used a system which relied on non rechargeable dry cells, (similar to a large flashlight battery, and which was not maintained by an electrical system as on modern automobiles) to start the engine or for starting and running at low speed. The operator would xb manually switch the ignition system  xb  over to magneto operation for high speed operation.

• Most four-stroke engines xb have used a mechanically timed electrical ignition system. xb The heart of the system is the distributor. The distributor xb contains a rotating cam driven by the engine's drive, a set of breaker points, a condenser, a rotor and a distributor cap. External to the distributor is the ignition coil, xb the spark plugs and wires linking the distributor to the spark plug xb sand ignition coil.
• The system is powered by a lead-acid battery system xb  which is xb charged by the car's electrical system using a dynamoor alternator. The engine system operates contact breaker points, which interrupt the current to an induction coil (known as the ignition coil).

Two complete sets of coils, breakers and condensers can be provided - one set for each half of the engine, which is typically arranged in V-8 or V-12 configuration. Although the two ignition system halves are electrically independent, they typically share a single distributor which in this case contains two breakers driven by the rotating cam, and a rotor with xb two isolated conducting planes for the two high voltage inputs. A single breaker driven by a cam and a return spring is limited in spark rate by the onset of contact bounce or float at high rpm. This limit can be overcome by substituting for the breaker a pair of breakers that are connected electrically in series but spaced on opposite sides of the cam so they are driven out of phase system xb .