A data transmission method entails differentially transmitting low-pass filtered first outgoing data to and through an isolation transformer at a first data rate. Second outgoing data is differentially transmitted to and through the transformer in the same direction as the first outgoing data but...http://www.google.de/patents/US5799040?utm_source=gb-gplus-sharePatent US5799040 - Method for transmitting and/or receiving data at different data transfer rates especially in applications such as dual-rate ethernet local-area networks 
