baud

(Bd)

   a unit used in engineering for measuring the rate of data transmissionover telegraph or telephone lines. The baud rate is the number of distinctsymbols transmitted per second, that is, the number of times per second thesignal carrying the communication varies in strength or frequency. In thedays of the telegraph, the signal increased at the start of a pulse and decreasedat the end, so the baud rate was 2 times the number of dots that could betransmitted per second. In recent years, when the baud has been used to representdigital data transmission, the definition has varied according to the techniqueused. If the symbols transmitted have only two states (on or off) then thebaud rate is the same as the transmission rate in bits per second. This was the case in early modems, but in modern data transmissionequipment symbols have a much larger number of possible states. For example,if the signal has 2⁸ = 256 possible states, then a single symbolcan carry 8 bits of information and the bit rate will be 8 times the baudrate. Consequently, any use of "baud" as a synonym for "bits persecond" is incorrect. The baud is named for the French telegraph engineerJ. M. E. Baudot (1845-1903), the inventor of the first teleprinter.