Abstract: A hydraulic system includes a primary function control valve connected to the output of a highly responsive variable displacement pump and having a power-beyond port connected for supplying fluid to a secondary function control valve. The secondary function control valve has a power-beyond port connected to a displacement controller which is responsive to the flow for increasing or decreasing the displacement of the pump respectively in response to decreases and increases in power-beyond flow from the secondary function control valve.

Abstract: The displacement controllers of a first variable displacement pump supplying fluid for hoe and travel functions of an excavator and a second pump supplying fluid for the excavator house swing function are connected to shuttle valves which operate to couple to the controllers the lesser of the power beyond fluid pressures emanating from travel function and swing function control valves. A bypass circuit is arranged to couple power beyond flow from the swing function control valve to join the flow being outputed from the first pump when the pressure of the last-named power beyond flow exceeds the lesser of that emanating from the travel control functions. Lead compensators are provided to make the controllers more responsive to circuit demands and a power limiting valve is provided for automatically connecting pressure for destroking the pumps to relieve engine load when the engine speed falls to a predetermined minimum.