Abstract: A power transmission system serves to drive a variable-speed processing machine normally in a lower speed range and if necessary in an upper speed range. The system essentially comprises the following elements which are all disposed coaxially to one another: An input shaft connected by means of a hydrodynamic adjustable coupling to an intermediate shaft to rotate the impeller pump of an adjustable hydrodynamic torque converter. Its turbine wheel rotates with a brakable override shaft. The intermediate shaft and the override shaft are connected to an output shaft by means of a differential gear.