Previously recommended methods of transmitting facsimile data on the telephone network resulted in periods of time when there is no signal present in the network; one consequence of this was that the retraining time required for the facsimile modem's receiver after each quiet period was undesirably long. This problem is solved by the high-speed transmitter sending two or more holding tones whenever it is not sending training or facsimile signals; these tones prevent re-routing of a telephone connection and allow the high-speed receiver to continue to track data clock and carrier frequencies, thereby considerably reducing the time required for retraining.