The Free On-line Dictionary of Computing (30 December 2018):

remote echo

    (Obsolete: "full-duplex") A mode of operation
   of communicating programs or devices in which the sending
   system does not display the characters the user enters, but
   only sends them to the remote system which then "echoes" them
   back to be displayed to the user.  This lets the operator see
   not only typing errors, but also transmission errors.  This is
   now the usual mode of most systems with remote users.

   Contrast: local echo.

   (2000-03-30)