Baud rate extension generates a lot of questions, due to the popularity of higher baud rates these days. Baud rate extension is a way of translating the entire baud rate table up one or more "notches". With baud rate extension set to 1, you use your applications normally, but when stty thinks you're running 9600, you're actually running 19,200. When stty thinks you're running 38,400, you're actually running 57,600. It's sticky across opens and closes, so you don't have to keep setting it every time a new process is spawned on the line.