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Glossary
V
V.25bis: An ITU-T standard for synchronous communications between a mainframe or host and a modem using HDLC or other character-
oriented protocol.
V.54: The ITU-T standard for local and remote loopback tests in modems, DCEs and DTEs.  The four basic tests are:
•  local digital loopback (tests DTE send and receive circuits),
•  local analog loopback (tests local modem operation),
•  remote analog loopback (tests comm link to the remote modem), and
•  remote digital loopback (tests remote modem operation).
Virtual Circuit: A logical connection.  Used in packet switching wherein a logical connection is established between two devices at the start
of transmission.  All information packets follow the same route and arrive in sequence, but do not necessarily carry a complete address.