Abstract: The invention relates to a data transmission device between two separate lines. This device comprises a real terminal (TRA, TRB) and a virtual terminal (TVA, TVB) associated with each of the lines. The state of a real terminal is that of the associated line. The state of a virtual terminal indicates whether the associated line is transmitting or able to receive a data. Each real terminal associated with a line controls the state of the virtual terminal associated with the other line by means of a control signal (COM), while said virtual terminal controls the state of its associated real terminal (CTRL), and accordingly of the line. A virtual terminal associated with a receiving line receives the control signal (COM) coming from the real terminal associated with the other line and inhibits (INH) the real terminal associated with this receiving line. The inhibited real terminal of the receiving line accordingly is no longer capable of sending a control signal (COM) as long as the other line is transmitting.