DDX-C is a digital public telephone service for switching lines while allowing high speed, high quality data transmissions using digital lines. Since communication service charges are based on time and distance just as with normal telephone calls, this service is particularly well suited for transmitting large amounts of data such as data files or motion video data in a short amount of time. Since this service is not connected to the telephone network it is necessary for both sender and receiver to have contracts with NTT for DDX-C service.

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