A bidirectional communication system which provides a wide variety of communication services to meet the needs of broadcast audiences. Each client terminal sends a service request message over a communications network and receives authorization, and after that, it transmits and receives the video information....http://www.google.com.hk/patents/US6477708?utm_source=gb-gplus-share專利 US6477708 - Bidirectional communication system, client terminal, client management server, and broadcast server
