TopWorx D-Series: the proven workhorse in the most demanding applications. The all Emerson on/off valve controller with the most reliable proximity switch and solenoid pilot valve on the market, it is your guarantee that your solenoid valve will work on demand and offers considerable cost savings over the life of your process. Additional features include a quick response time, intrinsically safe approval, and internal mounting for protection from the environment. Not all switches are created equal.