| 摘要 |
<p>PURPOSE:To perform the modulation/demodulation of a scramble sigpal by providing a first line signal detection circuit to generate output after the lapse of a constant time when a line signal arrives, and a second line signal detection circuit to generate the output after the lapse of the constant time different from the above constant time. CONSTITUTION:A line signal (a) in which no scrambler circuit is inserted to a transmission side and a line signal (b) in which it is inserted are supplied to a demodulation circuit 1, and their demodulation signals (d) and (c) are supplied to a decision circuit 6, respectively. A first line signal detection circuit 5 generates the output signal (g) after the lapse of a time T2 after the arrival of the line signal, and a second line signal detection circuit 7 generates the output signal (e) after the lapse of a time T1(T1<T2) after the arrival of the line signal. The output of the decision circuit 6 makes a selection circuit 3 operate so as to select the output of the circuit 1 for the signal (d), and makes the selection circuit 3 switch so as to select the output of a de-scrambler circuit 2 for the signal (e). A 2-input gate circuit 4 is outputted as the signal (h) after eliminating undefined data by the signal (g).</p> |
