| 摘要 |
A line terminal circuit comprises a buffer section (A, D) for connection to a transmission line (TL) and for performing at least one of the functions receiving signals from said transmission line and transmitting signals via said transmission line; a controllable current source section (S1, S2) connected to inject or withdraw a current (Iu, Id) into or from a node (ND1, ND2) between said buffer section and said transmission line in accordance with a current control signal (CS); and a common mode voltage control section (CT) for detecting a common mode voltage component on the transmission line (TL) connected to the buffer section (A, D) and for generating said current control signal (CS) in response to said detected common mode voltage component and outputting said current control signal to said current source section (S1, S2); said common mode voltage control section (CT) being adapted to output said current control signal (CS) such that said common mode voltage component is within the limits of a predetermined voltage interval (Vrefh, Vrefl).
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