What is a camshaft synchronizer?

A camshaft synchronizer is a device driven off the camshaft that couples to a sensor that tells the car's powertrain computer at what point of rotation the camshaft is. The information from the sensor is used by the powertrain computer to time the spark that will ignite the air-fuel mixture in the cylinders. Many engines using camshaft synchronizers are older designs that were originally designed to have a conventional distributor; the camshaft synchronizer mounts in the same place as the distributor used to.