The following answer is obtained by our Internet Research Algorithm : Microprocessors are used in control system of locomotives. The microprocessor based control and fault diagnostic system has been developed for conventional electric locomotives including locos provided with static converter. It performs logical control of the locomotive by continuously monitoring various digital/ analog inputs and checks for any abnormality in the operation. Micro controller in locomotives are used to monitor and control the shaft speed And it is used as a main control unit to control the process of the whole system.