operation of a communications program or device in which it
displays the characters the user enters at the same time as it
sends them to the remote system.
In communications between computers or computing processes,
particularly those involving human keyboarding and/or reading,
duplex came to mean the re-transmission of a keyboard
character to the output display.
Early input device such as the Teletype
ASR-33teleprinter, being descended from the electric typewriter,
printed all input characters as they were typed (i.e. they did
local echo). Local echo was typically optional on the
videoterminals that replaced them, and usually disabled in favour
of
remote echo. A disadvantage of local echo is that it
will continue, even when the communication circuit has failed,
which can be misleading.
(2000-03-30)