TOPWORX DXP-L21GN4S162 Valve Limit Switch | Industrial Position Monitoring The TOPWORX DXP-L21GN4S162 Valve Limit Switch is an industrial valve position monitoring solution designed to provide reliable feedback about the operating state of automated valves. By identifying valve movement and communicating position information to a control system, it helps operators and automation equipment understand whether a valve has reached its intended operating condition. In industrial