The OSYSU-EX is designed to supervise the position of an Outside Screw & Yoke type gate valve in hazardous locations. The device mounts on the valve to monitor the rising stem. When properly mounted, the trip rod will be resting in a groove filed into the valve stem. When the valve stem begins to move, caused by closing the valve, the trip rod will be pushed out of the groove and activate the switch. To aid with installation the trip rod length is adjustable. This device features a UL listed explosion proof switch enclosure.