| 摘要 |
PURPOSE:To prevent the degradation of materials when broadcasting materials are recorded especially, by setting automatically an optimum recording current value or an optimum recording bias current value which is changed in accordance with replacement of a used magnetic tape or a magnetic head or the variation of the wear of the magnetic head. CONSTITUTION:When the average amplitude value of a driving output signal 10 exists at a point (a), the output of a reproduced signal 13 is increased in the half cycle, where an amplitude modulated signal 6 increases the recording current value, with respect to the reproduced signal amplitude, and the output of the reproduced signal 13 is reduced in the half cycle when the signal 6 reduces the recording current value. When the average amplitude value of the driving output signal 10 exists at a point (c), the reproduced signal is changed with a polarity opposite to that in said case where the average amplitude value exists at the point (a). When the average amplitude value of the driving output signal 10 exists at a point (b), the output of the reproduced signal 13 is reduced by the same quantity in the half cycle when the recording current amplitude value is increased and the half cycle when it is reduced. Thus, the waveform and the polarity of the output of the reproduced signal 13 are discriminated to detect whether the recording current value is to small, too large, or proper. |
