| 摘要 |
PURPOSE:To contrive the improvement of the transmission quality by providing a voltage detection means, an impedance interposed between each of balanced lines and ground and an adjusting means adjusting the impedance so as to detect the unbalance of the transmission lines and controlling the impedance control means, thereby improving the resistance against the common mode noise. CONSTITUTION:An output signal from an unbalance detection circuit 100 is led to an A/D converter circuit 210, where the signal is converted into a digital data and the result is fetched in a latch 220. A decoder 230 uses a data from the latch 220 to control an impedance correction means connected between an A line 530 and ground. Plural combinations of relay contacts and resistors are connected in parallel between the A line 530 and ground. Resistors 270, 271, 272 and 273 have different resistance respectively and the impedance between the A line 530 and ground is adjusted. The impedance control circuit of the same constitution is connected to the line B, and the degree of unbalance between the lines A and B is minimized by closing both relay contacts selectively.
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