| 摘要 |
PURPOSE:To prevent illegal duplication by obtaining the special constitution of a vertical synchronizing pulse in a vertical blanking section, an equalizing pulse, and a horizontal synchronizing pulse in a picture-recorded video tape for a helical scanning revolving two-head system video tape recorder. CONSTITUTION:In a vertical synchronizing signal section B in a vertical blanking section E, only a pulse BIA with the width of 1-20mu second equivalent as a vertical synchronizing pulse to be separated by a vertical synchronizing signal separating circuit is present and at least one part of all of vertical synchronizing pulses, equalizing pulses, and horizontal synchronizing pulses of the vertical blanking section records a complex video signal which is a pedestal level P or below onto at least one part of a tape. When the modification soft tape is dubbed by using two VTRs, a mechanism to separate and 1/2-frequency-devide the vertical synchronizing signal and to generate a control signal does not function and the control signal is not recorded onto an illegal copy tape. By the electric resistance and the stray capacity of a cable to connect the two VTRs, the pulse BIA is integrated and recorded onto the illegal copy tape and does not function as the vertical synchronizing signal any more. |
