X21

1 definition found

From The Free On-line Dictionary of Computing (27 SEP 03) [foldoc]:

  X.21
       
           A digital signaling interface
          recommended by {ITU-T} that includes specifications for
          {DTE}/{DCE} physical interface elements, alignment of {call
          control} characters and error checking, elements of the call


          control phase for {circuit switched} services, data transfer
          at up to 2 {Mbps}, and {test loops}.  64 {kbps} is the most
          commonly used transfer rate.
       
          (2000-02-28)