JMS Industrial Dustproof AC consists of a continuously variable auto transformer operated by an AC steps synchronous motor, a buck-boost transformer and IC based control circuit.The control circuit continuously monitors the output voltage and looks for error in the output and is immediately corrected by witching on the servo motor in appropriate direction in order to induce the required voltage through the series connected buck-boost transformer. As soon as the voltage reaches the desired level the motors is switched off. The High and Low indicators on the panel indicates the status of incoming mains supply. In the manual mode the voltage could be increased or decreased by pressing the switch in either director. The output adjustment facility has been provided adjust the output voltage as per requirement.