Remote data transmission (RDT) was a term used in the 1980s, primarily in Germany, for the transmission of data between computers over a medium using a communications protocol. At the time, the most widespread form was RDT over the telephone network.Other transmission media like radio waves or light were also used. Most RDT now uses the Internet. In German speaking areas, RDT is used in the special sense of the considerably more narrowly defined Electronic Data Interchange (EDI).