Abstract: A fluid flow control device comprising a housing, an inlet at one side of the housing and an outlet at its other side, and externally-controlled valve means installed within the housing for controlling the flow of the fluid therethrough, characterized in that the interior of the housing is divided into at least two compartments, each having an inlet port and an externally-controlled valve within the compartment for controlling the passage of fluid through the respective inlet port, at least one of the valves being adapted to control the fluid flow through the housing in the direction from the inlet to the outlet thereof.