Named for telegraphy pioneer Jean Maurice  Emile Baudot (1845-1903), this is a unit that measures the number of  changes, or transitions, that occur in a signal in each second. So,  if the signal changes from a “one” value to a “zero”  value (or vice-versa) one hundred times per second, that is a rate of  100 baud.
Modern modems use advanced  modulation techniques that encode more than one bit of data into each  transition. A 28,800 bps modem typically encodes nine bits into each  transition; it runs at 3,200 baud, not 28,800 baud (the latter number  being the product of 3,200 and 9)
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