In a information distribution system, a control channel modem that provides independent communications channels for bi-directional message traffic between a service provider and a set-top terminal located within a subscriber's home. The modem transmits messages, control information and status information...http://www.google.com.tw/patents/US5896414?utm_source=gb-gplus-share專利 US5896414 - Method and apparatus for providing control channel communications for an information distribution system
