For example, the ITU V.21 standard used audio frequency-shift keying with two possible frequencies, corresponding to two distinct symbols (or one bit per symbol), to carry 300 bits per second using 300 baud. The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal. Historically, modems were often classified by their symbol rate, measured in baud. Modern broadband modems are typically described in megabits.
Modems are frequently classified by the maximum amount of data they can send in a given unit of time, usually expressed in bits per second (symbol bit/s, sometimes abbreviated 'bps') or rarely in bytes per second (symbol B/s).
