In telecommunications, the Baud is a measure of symbols transmitted per second in a modulated signal. It is named after Emile Baudot, the inventor of the Baudot code for telegraphy.
The term "baud" is sometimes misused to refer to "bits per second"; though it is possible for one event to carry one bit, it is more common to make more efficient use of bandwidth by transferring several bits in one event. Thus, a 2400-bit/s modem actually transmits at 600 baud, where each quadrature amplitude modulation event carries four bits of information.
A small note: When a search is done on "baud" at dictionary.com, there is a definition and example there that states that 1 baud can equal anywhere from 1 bit to 16 bits of data per cycle.
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