| 摘要 |
PURPOSE:To attain the switching of a reference signal formed from an output of a framing detection circuit and an output of a field discrimination circuit out affected by skew by comparing the framing detection circuit and the field discrimination circuit for their outputs to detect the skew and providing a changeover switch. CONSTITUTION:When no skew exists, a Q' output of a D flip-flop 2 is outputted as a reference signal and even when a skew takes place, since an output of a field discrimination circuit 5 is a correct framing signal, D and B signals are compared by an exclusive OR gate 9 to form a signal (c). Only when the skew takes place, an output of an integration filter 10 goes to an H level. On the other hand, an output of a D flip-flop 2 is inputted to a monostable multivibrator 7, its output signal D latches the signal B to form a signal E. The signal is susceptible to noise but immune to the effect of skew, and when a skew takes place, a switch 11 is changed over to the position C to output a signal F as a reference signal. Thus, a framing servo function immune to either noise or skew is obtained.
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