| 摘要 |
PURPOSE:To establish the AGC circuit effective to wired communication, by detecting the output of the variable gain amplifier, comparing and discriminating it with the reference signal level, and giving the signal in A/D conversion for the output to the set gain value of the amplifier with partial D/A conversion. CONSTITUTION:The input signal is amplified 2 via the variable gain amplifier 1, outputted and detected 3. The output of the detector 3 is compared and discriminated with the reference voltage A at the comparison circuit 4, and the error signal is DC-amplified 5 and converted into a digital value at the A/D converter 6. The partial D/A converter is provided in the converter 6, and analog signal value converted is fed to the variable gain amplifier 1 as the gain control value to control the gain. When the output of the comparison circuit 4 is stable, the A/D conversion of the converter 6 is stopped, the D/A conversion output is held constant at the sampling hold circuit to control the amplifier 1. Accordingly, if the transmission condition is once determined, since the setting of the reception gain is easily preset and it is stably held until the specified information communication is finished, it is effective to the facsimile communication. |
