a method is disclosed for transmitting super - rate data signals having a bit - rate higher than a predetermined bit - rate through a digital data transmission system normally providing channels having the predetermined bit - rate . the channels are subject to different propagation delay characteristics through the system . the method , comprises allocating a group of k channels in the data transmission system as a virtual channel for the transmission of the super - rate signals ; dividing the super - rate signals into n sub - signals , where n ≦ k , having a bit - rate equal to or less than the predetermined bit - rate ; generating delay calibration signals for transmission through the data transmission system ; defining an overhead channel in at least one of the channels ; transmitting the n sub - signals over the channels ; transmitting the delay calibration signals in a rotational pattern over the channels in slots normally containing data signals , the delay calibration signals temporarily displacing the data signals normally occupying the slots ; transmitting the displaced data signals over the overhead channel in slots normally occupied by the delay calibration signals displacing them ; and reassembling the n sub - signals to reconstitute the original super - rate data signals with the aid of the delay calibration signals after transmission through the channels .