Change-speed gearbox, in which an input shaft is connected to an output shaft by at least one first and one second component transmission arranged parallel to one another in a power flow circuit and each have a frictional power-shift clutch and an intermediate shaft, each of the intermediate shafts being operatively connectable to the input shaft by the power-shift clutch, and with at least one gearbox constant per component transmission, each gearbox constant having a gearwheel on one of the two intermediate shafts, at least one of which gears is operative to be operatively connected to a first layshaft arranged parallel to the input shaft, wherein at least one gearbox constant is operative to be brought into operative connection with the first and the second power-shift clutch.