A communications system includes a communications device having a plurality of access modules each having a port and connected to a communications line and a plurality of transmitters with the respective transmitter associated in one-to-one correspondence with the communications line of an access module. Each transmitter has a line driver and is configured to couple communications signals to a respective communications line. A voltage source is connected to the line drivers and configured to provide a bias voltage to the line drivers that varies depending on a selected minimum power level. A controller is connected to the voltage source and has logic configured to change the bias voltage to the line drivers. The controller is responsive to a minimum data rate for each bias voltage.