| 摘要 |
PURPOSE:To eliminate noise at the time of track changeover without deterioration of reproduced picture and sound quality by using output signal of AFC circuit of fixed phase for reproducing horizontal synchronizing signal and controlling so that the time of reproducing track changeover coincides with zero cross point of periodical noise. CONSTITUTION:Reproducing signals taken out by a reproducing head 2 or 3 are inputted to a changeover switch circuit 6, changed by the circuit 6 and demodulated by an FM demodulator 9 and held in a preholding circuit 11. Reproducing horizontal synchronizing signals 19 are inputted to a phase comparator 21 of a noise eliminating circuit. An AFC circuit is constituted of the comparator 21, a loop filter 22 and a VCO23. Output signals of this AFC circuit are inputted to a monostable multivibrator 15 as trigger signals. Output of the multivibrator 15 is inputted to a D-type FF17 which inputs a reproducing track changeover signal. The output of the FF17 controls the circuit 6, and at the same time, controls the circuit 11 through a holding signal generating circuit 25. Thus, malfunctions due to drop out etc. near the time of reproducing track changeover are prevented. |
