side by a spring 40 which forces the valve spool 26 into its closing position in which both passages are blocked in addition each end of the valve spool 26 is subject to a control pressure which urges the valve spool 26 to the opposite position the control connections of the valve 24 are each connected to a selector valve 42 44 each of the two selector valves is a 3 2 way valve they are coupled to each other mechanically as indicated by the rod 46 and can be operated together in various ways for example electrically hydraulically or mechanically by an actuator 48 most appropriately the two selector valves 42 44 are configured as a combined valve spool they are shown as separate parts only for the sake of clarity the position of the selector valves 42 44 shown in fig1 corresponds to the open center operation in which a hydraulic device with its center position open and designed for constant flow operation is connected to the valve arrangement 16 in this position the control connection of the valve 24 located on the side of the spring 40 is connected to the reservoir 22 and the other control connection is connected to the supply line 34 leading to the control valve 12 if the control valve 12 is in its neutral position then the supply line 34 is connected to the reservoir 22 and does not carry any pressure thereby the two control connections of the valve 24 are connected to the reservoir 22 so that the valve spool 26 is moved into its position shown in fig1 by the force of the spring 40 and both passages.