This time, the operator has moved the controller and the pump discharge is to be lead to the hydraulic cylinder to lift. Study the diagram carefully. M P1 P2 M As soon as the operator moves the controller, a small amount of control pressure reaches the PLV on P1 (blue line). This will cause the PLV to stop draining the hydraulic pump pressure into the reservoir. Hence, all the delivery of the pump P1 reached the cylinder through the shuttle valve (red line).