| 摘要 |
<p>PURPOSE:To realize a variable speed reproducing function by a small-scale circuit easily, by detecting amplitude variation of a difference frequency component obtained by converting pilot signals of four kinds of frequency on the basis of a pilot of specific frequency and performing tracking control. CONSTITUTION:A reproduced pilot signal P0 is frequency-converted by a frequency converting circuit 31 with a pilot signal P2 from a pilot signal generating circuit 50 and the difference frequency component is outputted to detecting circuits 32 and 33. An amplifying circuit 34 amplifies the difference between outputs E and F of the circuits 32 and 33 and it is phase-inverted alternately according to pulses S from a circuit 15; and the output G is shaped into a rectangular wave signal and a pulse I is outputted every time it rises or falls. The output I is supplied to a frequency discriminating circuit 38, which outputs an error signal corresponding to variation of the pulse I. On the other hand, the output J of a frequency dividing circuit 42 is phase-compared with a reference signal to obtain an error signal, which is added to the error signal from the circuit 38 to supply the sum signal to a capstan motor 5, performing the tracking control.</p> |
