| 摘要 |
There is described a system for preventing unauthorised descrambling of scrambled programming signals which are transmitted over a CATV communication network (10) which includes a headend (12) and a plurality of settop terminals (20), the system including means for the selective relocation of the service data channel within the vertical blanking interval, thereby preventing unauthorised descrambling of programming by convention descramblers. Also described is a headend and a settop terminal for use in such a system. <IMAGE> |
