In a modem that transmits signals to and receives signals from a remote device at a multiplicity of communication rates, the quality of the channel is monitored, a communication rate is selected based on the channel quality, the desire for an increased rate is indicated, and the increased rate is implemented...http://www.google.es/patents/US4756007?utm_source=gb-gplus-sharePatente US4756007 - Adaptive communication rate modem
