| 摘要 |
<p>In order to control subscriber access to selected television programs in a CATV system, nonstandard horizontal synchronizing pulses, having a greater amplitude and either a higher or lower pulse repetition rate than the contained horizontal synchronizing pulses, are selectively added to those television programs to be controlled. As a result, the television receiver of a nonpaying subscriber interprets the nonstandard pulses as being valid horizontal synchronizing pulses thereby preventing the receiver from synchronizing its line scanning with that of the television program rendering the picture produced therefrom unviewable.</p> |
