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 DISCUSSION OF FULL AND HALF DUPLEX

 Technically, "full duplex" refers to a comunications setup in which
 both sides may transmit at the same time and "half duplex" refers
 to a setup in which only one side transmits at a time.  True full
 duplex is seldom used in RS-232 communications (although some "sliding
 windows" protocols do use full duplex).  When the terms "full duplex"
 and "half duplex" are used, they most often mean "remote echo" and
 "local echo" respectively.

 Remote echo means that when you type a character, your program sends
 it to the other end; the other end sends it back; and your program
 then writes that character to the screen.  It gives a more accurate
 representaion (on your screen) of what the other end is receiving,
 although line noise on the second transmission can give a false
 picture.

 Local echo means that when you type a character, your program sends
 it to the other end and also writes that character to the screen.

 Most services and bulletin boards use remote echo ("full duplex") by
 default, although some can be configured to your liking once you have
 established a connection.

 When setting up to connect to a new service, set your program for
 half duplex.  If you see each character twice on your screen, switch
 to full duplex.