The invention relates to a drivetrain comprising an internal combustion engine, at least one friction clutch having at least one disengagement device with a pressure relief device and a transmission. When a motion sensor unit detects any motion of the mobile device and creates a sensing signal corresponding to the motion, a control unit of the mobile device sets a touch lock function to a locked state or an unlocked state, depending on the sensing signal. The control circuit includes a detector circuit that detects whether a band switching pulse signal is superimposed on the pulse signal, the detector circuit including a converting circuit that converts a frequency of the band switching pulse signal into an integrated value for the detection of the band switching pulse signal.