A conversion structure is provided for converting polarity changes into digital characters and digital characters into polarity changes. The structure includes a conversion circuit which is connected to a termination circuit by way of a memory unit, a communications control unit, and a second termination circuit which operates as an interface. Memory cells are assigned to receive incoming information and transmit the same to the conversion circuit and to receive outgoing information from the conversion circuit and transmit the same to the outgoing side of the termination circuit. The conversion circuit comprises an input code converter, and output code converter and a chain of series/parallel converters and parallel/series converters therebetween. The series/parallel converters receive polarity changes and convert the same into a digital character. Conversely, the parallel/series converters receive complete digital characters in parallel and process the same into a series of polarity changes.