Abstract: The present invention allows a modem to operate in both the voice band, from 300 to 3400 Hz, and also in the ADSL band, which extends above 3400 Hz. Unlike conventional ADSL modems, the present invention avoids the computationally-intensive operations required to extract all the available band of a telephone subscriber loop. Consequently, the present invention can be implemented with low-cost modifications to existing voice band modems. The present invention thereby offers higher data transfer rates at a fraction of the cost of more complicated ADSL modems. The present invention also provides bypassing functions, which allow communications through a modem located at the telephone central office side of a subscriber loop to be switched through a packet-switched network, which is capable of accommodating high data transfer rates, instead of a central office switching system, which generally imposes unnecessary limitations on data transfer rates.