| 摘要 |
<p>PURPOSE: To prevent malfunction generated due to a residual signal and a noise by adjusting the pulse width of a Schmidt trigger according to the size of a control pulse further proportional to the moving speed of a tape. CONSTITUTION: A control signal read from a video tape by an audio control head 1 is amplified by an amplifier 2 and rectangular wave-converted by a Schmidt trigger circuit 3. At that time, index information using duty is included in the rectangular wave. Then, this rectangular wave signal is inputted to a VIS operating circuit 4 and a VIS function is executed. On the other hand, a microprocessor 5 provides each kind of speed signal of a video tape to the Schmidt trigger circuit 3, and the circuit 3 adjusts a trigger width by using this. That is, the Schmidt trigger width at the time of the forwarding high speed winding/rewinding of the tape is changed so as to be larger than a noise or a residual signal and smaller than the control pulse, and the VIS operating circuit 4 is operated only by the control pulse.</p> |
