A valve uniquely integrates ball valve and throttling valve principals, thus affording quieter stop-and-start operation. A ball held by two seat rings is rotatable ninety degrees and has a diametric bore adjustable between fully closed (0.degree.) and fully open (90.degree.) positions. Oppositely disposed, relative to both the ball and the valve's longitudinal axis, are two plate assemblies each describing a tortuous fluid path. Each ring has conduits communicating with an assembly's tortuous path and communicable with the bore so that, sequentially during the ball's 0.degree. to 90.degree. rotation: the ball seals off the conduits, no fluid passing through the valve; all fluid passing through the valve flows through the plate assemblies and conduits; some fluid passing through the valve flows through the plate assemblies and conduits, some fluid passing through the valve flowing freely; the ball seals off the conduits, all fluid passing through the valve flowing freely.