Method and apparatus for providing a regulated and current limited power source to support bidirectional telephone delivery circuitry and methods for a multiplicity of telephone subscriber lines to a downstream distribution terminal using only two preexisting transmission lines for carrying the regulated...http://www.google.es/patents/US6763109?utm_source=gb-gplus-sharePatente US6763109 - Copper based interface system and regulated power source
Copper based interface system and regulated power source
