An on demand services feature for the provision of video, audio, and data services for a subscription system of the CTV type, or the like. The system comprises a headend coupled to a distribution network having a multiplicity of subscribers. Standard service signals forming scheduled program channels...http://www.google.com.hk/patents/US5631693?utm_source=gb-gplus-share專利 US5631693 - Method and apparatus for providing on demand services in a subscriber system
