The Victaulic® Series 748 FireLock® Ball Check is used in the trim piping of the Series 756 Dry Valve and Series 758 Preaction Valve in order to allow the valve activating mechanism, either Series 753-A Dry Actuator or Series 754-A Accelerator, to monitor and react to the entire sprinkler system air volume. The Ball Check will remain fully open, allowing the free flow of air in both directions, until the sprinkler control valve is activated, at which time the flow of water entering the sprinkler system will close the Ball Check keeping the Air Supply trim from flooding. The Ball Check will remain closed until the sprinkler system is fully drained during the normal sequence of placing the sprinkler control valve back into service.