Breaker points

A mechanical switch in the distributor with two metal contact points (usually made of silver, platinum, or tungsten) that open and close. When the points are closed, energy is stored in the primary windings of the coil. When the breaker points open, this energy is transferred to the secondary windings of the coil and stepped up, resulting in a high voltage to fire the plugs. The air gap between the breaker-point surfaces is critical. If the gap is too small, the timing is retarded, if too wide advanced. Also called points, contact points, and ignition points.
See also dual breaker points, contact breaker point.