| 摘要 |
PURPOSE:To eliminate the need for adjustment at cable installation, by automatically adjusting an automatic balancing circuit matched to the line impedance at 2-wire side and a distance correction virtual line circuit network (BON) compensating the transmission loss depending on the line length, in an AGC system at a 2/4 wire converting point. CONSTITUTION:A signal inputted from a 4-wire input terminal 34 is transmitted to a transmission line via a transformer 9. On the other hand, a signal inputted from the line 7 is inputted to an AGC.AMP31 via the transformer 9 and outputted from the terminal 32. The input signal from the line 7 is inputted to a differential AMP15 via the transformer 9 from a 2-wire side input terminal 8. If a balancing circuit 14 is not matched, an error signal from the AMP15 is processed at a comparison circuit 16 and a control circuit 17 and a switched drive circuit 19 is operated, and the balancing circuit 14 in matching with the impedance of the line 7 is selected. The distance compensation of line length is made as the results of the check of transmission loss by the driving switch circuit and the selection of resistors 24-26 for distance compensation of a BON28. |
