Baud Rate can be roughly defined as the speed of transmission of data between two computers. All forms of communication using the Serial Port requires the presence of four parameters: the baud rate of the transmission being the very first parameter, then comes the number of data bits encoding a character, the third in line is the optional parity bit, and last one is the number of stop bits. Each character transmitted using this method uses a character frame that has a single start bit, then data bits, the parity bit which is optional, and lastly the stop bit(s).

For instance, a transmission at a baud rate of 1 kBd or 1 kilo Baud is equivalent to a symbol rate of 1,000 symbols per second. A regular modem operating at this rate would send a thousand tones per second over the serial line.

So Baud rate is actually a measure of how rapidly data is moving between the two computers or other interface instruments using serial communication. The RS-232 interface uses basically two digital voltages, called MARK which represents some form of data and SPACE to act as a delimiter. A negative voltage is used to represent the MARK and zero volts often referred to as ground voltage is used to represent the SPACE.

Using the RS-232 standard which basically uses just two voltage levels, referred to as MARK and SPACE the baud rate is the same as the maximum number of bits of data, which includes the "control" bits, the data bits, the optional parity bit and lastly the stop bit(s).

The term baud refers to Emile Baudot, who invented the Baudot code for telegraphy. Since the unit adheres to the SI standard of units, the first letter denoting the symbol ?Bd? should be in upper case but when the whole unit's name is written (baud), it needs to be written in lowercase except when it is found in the beginning of a sentence.