| 摘要 |
PURPOSE:To prevent a magnetic tape medium from a defect of drop-out, by returning gain to the initial value once when the reading signal level of an ARA burst does not reach a reference level, and then repeating the operation to start the adjustment of the gain again. CONSTITUTION:An ARA burst signal read out from a reading head 12 is amplified by the gain at that time in a reading amplifier 13 and inputted to a comparator 16. A reference level VREF is applied to the comparator 16 and the output of the ARA burst signal is compared with the reference level VREF. At the initial stage, a counter 15 is set up to the initial value by PRESET DATA, the gain of the reading amplifier 13 is low and the output of the amplifier 13 is lower than the reference level VREF, so that the output ERR of the comparator 16 is turned to ''1''. Therefore, an AND circuit 14 sends a clock signal CLOCK to the counter 15 in every input of the clock signal CLOCK. A magnetic tape device applies a signal COUNT START to enable the counter 15 at the leading end of the ARA burst to the counter 15 to start the addition of the counter 15. |
