The M200-ST3 is most commonly used to detect the speed of engines used in generating sets. The pick-up, situated close to the flywheel, produces a high frequency pulse train directly proportional to the number of teeth passing it. The frequency is converted by the ST3 into a mA signal directly proportional to the rotational speed of the flywheel. The relay provides the user with the following adjustments, which allows the control of start up and normal running and protects against over and under speeds of the generator. Adjustment of crank speed 10 to 50% Adjustment of under speed 50 to 100% Adjustment of over speed 100 to 133 % A mA output signal proportional to input frequency. Typical start-up as follows -When the speed of the motor reaches the crank set- point, the crank relay energizes, disengaging the crank starter. When the under speed set-point is reached, the under speed relay is energized and the motor is now in the normal running condition with all relays energized. Should an under or over speed condition occur the appropriate relay is de-energized. Two other safety features are incorporated; if the pick-up sensor input lead breaks the over speed relay will de-energize also the crank relay will only de-energize when the input frequency goes below 20% of the set-point. The mA output signal can be fed to digital or analogue meters scaled in speed, or to provide a control signal to a PLC etc.