Abstract: A control device for a drive unit, preferably the drive unit of a power vehicle, is provided having a hydrostatic transmission where the adjusting device of the latter and the adjusting device of the internal combustion engine are controlled by means of a servo piston loaded by control pressure, whereby the internal combustion engine is prevented during reversing from being adjusted to an increased power output through a circuit before the adjusting device of the hydrostatic transmission has passed through the zero-stroke position, and where the circuit has two shut off valves whose outlets are connected with a line, which are connected to the spring-side pressure chamber of the operating cylinder of the internal combustion engine through a multiway valve.

Abstract: A control for working machine equipped with a continuously hydraulic drive unit and an adjusting element therefor in which the adjusting element is adjusted by control pressure, which is in turn adjusted by a control pressure adjusting element is provided having at least one restrictor in the control pressure adjusting element and a control pressure modifying element that influences the control pressure connected to the control pressure adjusting element.

Abstract: Vehicles with differential speed steering are provided having a hydrostatic transmission on each side for driving the drive wheels on that side, a spring-loaded servo piston operating a final control element of each transmission, at least one control pressure pick-off connected to the operating cylinders for controlling forward and backward travel, a pair of second control pressure pick-offs connected with the operating cylinders for controlling turning, a manually controlled pilot valve in a connection between the second control pick-offs and the operating cylinder and a control pressure reducing valve acting on the second control pressure pick-offs reducing the pressure to prescribed characteristics independently of the incoming pressure with respect to the actuation path.