Track scan initiation and cutout arrangement for a helical scan video recorder

In a helical scan video recorder adapted for reproducing video signals modulated on a high frequency carrier and fixed on a track of an elongated magnetic tape, the tape being adapted to be helically wrapped around a drum that is rotatable about its axis, the recorder including a magnetic pick-up head rotatable in a scanning path with the periphery of the drum for detecting video signals modulated on the tape as the tape is longitudinally advanced, means for longitudinally advancing the tape, means responsive to the detected envelope of the video signal for generating an error signal whose mean amplitude is proportional to the instantaneous amplitude of deviation of the video track from the scanning path of the magnetic head, and tape velocity regulation means connectible to the output of the error signal generating means and cooperable with the tape advancing means for varying the advance of the tape in accordance with variations of the error signal to correspondingly vary the amplitude envelope of the video signal detected by the head, the improvement which comprises, in combination, storage means coupled to the error signal generating means for continually storing the last-occurring mean amplitude of the error signal, first switching means effective when in a normal first position to couple the output of the storage means to the input of the tape velocity regulation means, said first switching means being operable from the first position to a second position to couple the output of the error signal generating means to the input of the tape velocity regulation means, and means responsive to the detected envelope of the video signal and rendered effective when the amplitude of such detected envelope exceeds a predetermined level for operating the first switching means from the first position to the second position.