| 摘要 |
PURPOSE:To obviate generation of noise even if the tape speed of a VTR on which an FM sound signal is recorded together with a video signal is made different from the speed in the stage of recording by detecting the envelope of a reproduced FM luminance signal, detecting the decrease in the level thereof and substituting the sound signal reproduced by the same with the signal after one vertical period. CONSTITUTION:Heads A, B trace the tape pattern like bold lines when run at two times faster than in the stage of recording in a tape pattern of an azimuth recording system shown in the figure. The level of an envelope detector 22 is discriminated with a discriminating circuit 23 and the pulse shown in the figure (c) is generated in a range of a prescribed level or below and further the pulse shown in the figure (d) is generated. These pulses are impressed on an FF24. On the other hand, a pulse is generated by a head selecting pulse as shown in the figure (e) by a waveform shaping circuit 25 and is used as a reset signal for the FF24. A change-over circuit 20 wherein the FF24 is reset at the starting point of a trace b1 is changed over to a voice detector 21 side of a track B, and is changed over to a voice detector 19 side of a track A by the next (f) pulse and thereafter the same operation is repeated. The signal at a terminal 26 is therefore the signal with which the signal shown in the figure (h) is detected and substantially no noise is generated. |
