| 摘要 |
PURPOSE:To prevent an excessive output generation at a drop-out time, etc., by causing the gain of respective AGCs, which make the amplitude of read standard signals of a prescribed value, to agree with rhe gain of the majority of AGCs approximately. CONSTITUTION:Standard signals which are read by heads H1, H2... and are recorded with a fixed amplitude are amplified by gain control circuits AGC1 and AGC2. Gain adjustment operation end signals of AGC1, AGC2... make respective transistors of adder circuit ADD conductive, and circuit ADD generates a voltage inversely proportional to the number of AGC1, AGC2... where control adjustment is completed; and when the voltage becomes lower than the reference voltage set in comparator CMP, flip flop FF is inverted to close gate G. As a result, gain adjusting pulses through oscillator OSC are broken to fix the gain of AGC1, AGC2..., where gain adjustment has not yet completed, to the gain of the majority of AGC1, AGC2... where gain adjustment has been completed, so that the excessive gain adjustment of AGCs dependent upon generation of drop-out, etc., can be prevented, and no excessive output is generated. |
