| 摘要 |
PURPOSE:To eliminate adverse effect onto an audio signal and a video signal and to simplify the constitution of the system by utilizing only a sinusoidal wave whose frequency is a multiple of (n) of a fundamental horizontal frequency as a signal to be superimposed onto an audio intermediate frequency signal at a sender side. CONSTITUTION:An oscillation section 121 generates a sinusoidal wave whose frequency is nfH (fH is a horizontal frequency) synchronously with a synchroniz ing signal from a synchronizing separator circuit 113 and supplies the wave to an inversion switch 122. The inversion switch 122 inverts into a forward or a backward the nfH signal based on a control data from a data insertion device 133 and supplies the result to an AM modulator 102 as a privacy data QA. When the privacy data QA is extracted by a receiver side, the privacy data QA is converted inversely, reproduces an output data of a descramble timing data generating circuit 131 representing the synchronizing compression location to decide the generating timing of the expanded pulse. Thus, a key data of the descramble key data generating circuit 136 to apply inverse conver sion of the privacy data QA is sent to the receiver side via a formatter 137, an FSK modulator 138 and a mixer 104. |
