A comparator unit is used to compare an actual transmission time signal with a nominal transmission time signal and to produce a difference signal from the discrepancy, from which difference signal a correction signal is produced in a control unit. This correction signal is used to control a correction unit, which compresses or extends an applied input data signal, thus changing the phase angle of the output data signal so as to minimize the discrepancy between the transmission times. The discrepancy is corrected independently of the system clock, and the correction speed is set variably.
