Tracking servo system for helical scan VTR - uses additional read head to detect tracking signal mixed with video signal

摘要

The video tape runs over the magnetic head drum following a helical line. Within the drum are two rotating write heads (A,B): one (A) records the video or RM audio information and one (B) which records a tracking signal which is detected by an additional fixed head (C) to ensure that the write heads are kept accurately on the recording track. The signal from the fixed head is analysed by a circuit which can adjust the height of the video signal write head. The track following signal consists of the video information mixed with a l.f. fixed tone. The tone frequency is altered from track to track to prevent false locking on an adjacent track.