What is Echo?

What is Echo? Async Terminals Display Characters Full Duplex
Remote Echo Display

     Async terminals use an echo to display entered characters on the screen. The echo can be remote (provided by the host computer) or local (within the terminal). A remote echo requires a full-duplex transmission facility while a local echo does not. Consequently, many terminals use the "FDX" terminology to configure for remote echo and the "HDX" terminology to configure for local echo. Failure to configure the host to complement the terminal will result in either no screen display (no echo) or double characters (two echoes).

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What is Echo? Async Terminals Display Characters Full Duplex