Abstract: A depth control system for controlling the working depth of an implement. The depth control system includes a monitor having an automatic mode of operation and a manual mode of operation wherein the automatic mode of operation provides preset, discrete working depth positions for the implement, and the manual mode of operation provides a continuous range of selectable positions. The monitor receives input signals from a position sensor mounted to the frame of the implement, and the position sensor includes a movable arm in sliding contact with an actuator arm mounted to a rock shaft of the implement whereby movement of the rock shaft and actuator arm causes the movable arm of the position sensor to move and provide different input signals to the monitor corresponding to the different positions of the rock shaft. The monitor provides an output signal to a hydraulic valve for controlling one or more hydraulic cylinders which actuate the rock shaft in movement to position the working depth of the implement.