Contact breaker

A contact breaker (or "points") is a type of electrical switch, found in the ignition systems of spark-ignition internal combustion engines.

More recent engines use electronic means to trigger the spark, which eliminated contact wear and allows computer control of ignition timing.

The plate is most typically rotated by a centrifugal mechanism, thus advancing the ignition timing (making the spark occur earlier) at higher revolutions.

This gives the fuel ignition process time to proceed so that the resulting combustion reaches its maximum pressure at the proper point in the crankshaft's rotation.

This latter effect is largely prevented by placing a capacitor parallel across the contact breaker—this is often referred to by the more old fashioned term condenser by mechanics.