| 摘要 |
<p>PURPOSE:To control good tracking by varying a detecting reference value in order to make a regenerative detection probability of synchronizing signal fall in within the most suitable range. CONSTITUTION:Reproducing signals from two head are binarized by a comparator for digital conversion and then sampling processed by a clock pulse from a terminal 17 at a synchronizing pattern detecting circuit 19 which in turn outputs a pattern detecting signal Pc'. A counter 20 counts the detecting pulse Pc' for every period of a certain time and outputs a discrete value signal A. A comparator 22 compares the signal A with a detecting reference value B' from a reference value generating circuit 27, and when the discrete value of the signal A is >=B', a detecting signal C of the synchronizing signal is sent to a control circuit 23, and from the circuit 23 sampling pules SPa and SPb are outputted. A counter 25 is reset by a reset pulse from a counter 24 and outputs a discrete value signal D of the signal SPb. A control circuit 26 takes a load pulse from the counter 24 together with the signal D and sends a variable control signal to the circuit 27 which in turn outputs the reference value signal B' by which a generative detection probability is fallen into the most suitable range.</p> |
