In a CATV system, a digital head end transmits both an area code and such data containing a management number and a channel contrastive table to a terminal of each of areas; each terminal stores thereinto both the area code and the channel contrastive table; and the digital head end retrieves the corresponding...http://www.google.fr/patents/US6868550?utm_source=gb-gplus-shareBrevet US6868550 - Conditional access system of CATV
