Abstract: A valve for simultaneous valving in two separate hydraulic systems, the valve having two slides with each slide being attached to a bypass driving member through caged spring cartridges. If one of the slides jams the other slide is moved by the bypass driving member in the opposite direction to the direction in which the jam occurred. The jammed system slide includes a porting which is opened by the relative movement of the bypass driving member, placing that system in a bypass condition. The other slide is not effected and remains in full control of a tandem hydraulic cylinder to which such valves are connected. If each half of the tandem cylinder is sized for full thrust capacity, there is no degradation in performance during the jammed condition.