The basic principle of speed monitor is comparison of pulses received from sensor with standard pulses. The unit consists of two parts : CONTROL UNIT and “SENSOR PROBEâ€. The sensor is to be installed with its sensing face in close proximity of rotating object. On this object, flags are to be fixed. The sensor products strong electromagnetic waves, which get disturbed by the flags, giving rise to corresponding pulses. These pulses are fed to the control unit where they are compared with standard pulses to sense the speed.