Shift register delay line for detecting first and last active line of video image in television letterbox detector is useful for storing significant bits from data stream

摘要

A shift register delay line for sorting p significant bits input on line (24) has a set of cascading recirculating shift registers (30-35). After storing the p significant bits, the sniff registers recirculate their contents under control of the signal RB so that p bits are restored to their initial position after n-p shifts.