The Model BVMS is designed to monitor the fully open position of a ball valve installed in a sprinkler system. The BVMS will mount onto Wilkins 950XL, 950XLT, and 975XL Backflow Preventors. The Model BVMS has an internal switch, which is toggled when the ball valve is moved from the open position. The internal switch however, does not track the position of the handle or ball. When the ball valve lever handle is moved into the open position, an internal spring-loaded switch contacts the lever handle and is toggled into the secure position. When the handle is moved from the open position, the switch extends and is toggled into the tripped position. The switch has contacts for both normally open and normally closed operation.