A modem which can automatically switch between protocols at different signalling rates. The protocal with non-standard signalling rates has a training sequence which initially has distinctive frequency-domain characteristics. Thus, as soon as one modem begins to send a training sequence, the other modem...http://www.google.de/patents/US4956851?utm_source=gb-gplus-sharePatent US4956851 - Modem with remote speed-change capability
