A network communication system having at least two communication protocol modes, namely, a full power communication mode and a low power, limited communication mode. In the low power mode, the link is line powered and utilizes link pulses to represent binary 1s and idle line states to represent...http://www.google.com.au/patents/US5805597?utm_source=gb-gplus-sharePatent US5805597 - Method and apparatus for providing low power basic telephony type service over a twisted pair ethernet physical layer 
