Operation of autotracking system in various video playback modes

Video tape recorders using oblique line scanning heads have the capability of accelerating or slowing down the playback relative to the nominal speed. The video signal quality is determined to a considerable extent by the operation of the autotracking system. The basis of the ATS is the circuitry which matches the trajectory of the magnetic playback head on the tape surface with the recorded line at the nominal playback speed. This so-called nominal playback matching circuit must incorporate additional devices to speed up or slow down the playback. The development of a video tape recorder with the autotracking system (ATS) is discussed. Block diagrams of the system and its components are supplemented with traces of the various control voltages and circuit responses, as well as a drawing of the trajectories of the magnetic head for various special effect modes. A piezoelectric transducer is used to shift the head relative to the record track to produce stop-field, stop-frame or other special effects. It is indicated that such VTR ATS circuits are capable of slowing or accelerating the playback by a factor of 5 to 10 times the nominal speed.