Cruise Control automatically controls the speed of a motor vehicle by adjusting the accelerator so that the driver need not keep it depressed on long drives. For the central microprocessor to maintain a set speed by adjusting the throttle when the road gradient changes, it needs to get feedback on the actual speed of the vehicle. Reed switch and magnets are mounted on the vehicles wheel assemblies and generate square wave pulse counting output that is used for the cruise control as well for the ABS. The on-board electronics averages out the wheel speeds and uses this signal to calculate the engine RPM and then adjust the throttle.
