The present invention relates to a device for a transmission, comprising a summing planetary gear set (17) and a variator unit (13) and components that bring them into operative connection with each other and with an input shaft (1) and output shaft (3, 8) for influencing the output speed in a continuously variable manner at constant input speed. The device can be installed as a prefabricated module between an internal combustion engine and a conventional transmission of any configuration and is also suitable for splitting the drive power of an internal combustion engine among a vehicle drive and one or several power take-offs, with the speed of the vehicle drive and/or the speed of the power take-off being adjustable in a continuously variable manner by the device. The device is also suitable for retrofitting existing motor vehicles.