Line interface for combining a voice band signal and an XDSL signal on a twisted-pair copper line

A line interface (30) for combining a broad-band XDSL signal and a voice-band telephone signal in a copper duplex cable, where the voice-band signal, over and above the voice signal, carries a DC feed for the user telephone and, during the call phase, also a ring signal. The XDSL signal and the voice signal are coupled to at least one primary winding of a line transformer of which the secondary winding (40) pilots the telephone duplex cable (41). The secondary winding (40) is not DC-coupled with the duplex cable (41) and the ring and feed signals are injected into the duplex cable (41) by a circuit (43) realized in high-voltage technology and arranged in parallel with the secondary winding (40). A further inductive winding (45) performs the function of compensating the flow variations induced in the core (44) of the line transformer during the call phase.