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...http://www.google.ca/patents/US5982768?utm_source=gb-gplus-sharePatent US5982768 - Dual band modem for high bandwidth communications
