Method and apparatus for descrambling a television signal

摘要

An extension control signal for a vertical blanking interval (VBI) rises at a timing delayed from the last key signal before the VBI by 64 mu sec plus the time difference between the key signal and horizontal synchronizing signal section, and falls at a timing delayed from the first key signal after lack of the key signal detection by an extension period of the horizontal synchronizing signal section plus the above time difference.