local echo

communications (Obsolete: "half-duplex") A mode of

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-33

teleprinter, 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)