| 摘要 |
PURPOSE:To make an input change to correspond to an output change, by providing BPFs for low and high of read signals from a head and supplying outputs of the BPFs to the non-inversional input of a comparator by switching, and then, connecting the output signal of the LPF to an AD converter through a logarithmic amplifier. CONSTITUTION:A control section 8 first connects a change-over switch 3 to a terminal 103 side by using a signal (f) and, when signals of a quantity equal to the one turn of a disk are supplied, reads the output value of HF signals by using a conversion starting signal (g) after converting the output value into digital signals (h), and then, sets the value to X. Then the control section 8 switches the changeover switch 3 and sets another value obtained by performing the same process to Y. The X and Y thus obtained respectively represent HF frequency components and LF frequency components contained in read signals in decibel and (Y-X) decibel becomes a value indicating an overwriting characteristic. Therefore, the overwriting characteristic can be obtained in a short time without using any man power.
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