signal pressure in conduit 64 and the value represented by spring 101 exceeds the pump discharge pressure in conduit 104 in their 34 up 34 positions valves 91 and 65 provide direct fluid communication between reservoir 32 and chamber 22 in swash plate angle control cylinder 19 via conduits 93 102 and 105 thereby causing the pressure in chamber 22 to approach or even reach the pressure in reservoir 32 this results in a corresponding increase in the hydraulic fluid passing through the discharge outlet of pump 11 when the load sense pressure signal in conduit 64 decreases to the point that the sum of the pressure in conduit 64 and the pressure force represented by spring 101 is less than the discharge pressure of pump 11 in conduit 104 valve 65 is actuated to its 34 down 34 position interconnecting the first and second ports of valve 65 and transmitting hydraulic fluid through conduits 103 102 and 93 into chamber 22 the pressure in chamber 22 increases moving piston 18 upwardly to reduce the discharge rate of pump 11 under normal operating conditions valve 65 will oscillate between its two positions to maintain the pump discharge rate at a value required by the instantaneous load demand for consumer device 41.