Abstract: An interface. unit (1) for display of alphanumeric-data packets, includes an input connector and an output connector (3). The input connector (2) is connectable by a first connection to a first apparatus (11, 11?) for reproduction of an audio signal to which alphanumeric data are associated. The output connector (3) is connectable by a second connection to a second reproduction apparatus (12) having a display (13) and a telematic decoder of the data packets. The interface unit (1) further includes a treatment of the audio signal connected to the input connector (2). The treatment of the audio signal carries out a preamplification and a filtering in frequency of the audio signal. A processor (7, 8) is connected to the input connector (2). The processor (7, 8) extracts and carries out a telematic encoding of alphanumeric data. A signal-mixer unit (9) is connected to the treatment of the audio signal and to, the processor.