duplex high speed data

from The Free On-line Dictionary of Computing (8 July 2008)

Duplex High Speed Data
DHSD

   (DHSD) A term which describes a {full-duplex} channel that can
   carry 64 kilobits per second.

   This is the kind of service provided by an Inmarsat-B type
   portable earth station or a {leased line} (not {ISDN}).

   (1995-02-02)