A center facility transmits, together with a television signal carrying a broadcast program, a message directed to a particular terminal apparatus, address data indicating an address of the particular terminal apparatus, and information quantity data indicating a quantity of the message. Recognizing...http://www.google.com.au/patents/US5497186?utm_source=gb-gplus-sharePatent US5497186 - CATV system in which message reception can be confirmed by a viewer
