| 摘要 |
PURPOSE:To always set a suitable gain by detecting that the reading action of an original by a photoelectric converting means is stopped, responding to the detecting output and fixing the gain of a variable gain amplifying means. CONSTITUTION:A sensor 3 detects whether or not a motor 4 to convey an original is turning and adds a detecting output to a peak level control circuit 5. The control circuit 5, when the stoppage of the motor 4 is shown by the detecting output, judges that the conveyance of the original, namely, the reading action of the original is stopped. When the control circuit 5 judges the effect, the action of a peak holding circuit 2 with a switch is stopped. At this time, a variable gain amplifier 1 is fixed to the gain instructed from the peak holding circuit 2 immediately before the action of the peak holding circuit 2 and the gain is held. Thus, the reading action of the original is intermittently executed and a suitable gain can be always set.
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