In data communications, bits per second (abbreviated bps or bit/sec) is a common measure of data speed for computer modems and transmission carriers. As the term implies, the speed in bps is equal to the number of bits transmitted or received each second.
Larger units are sometimes used to denote high data speeds. One kilobit per second (abbreviated Kbps in the U.S.; kbps elsewhere) is equal to 1,000 bps. One megabit per second (Mbps) is equal to 1,000,000 bps or 1,000 Kbps.
Computer modems for twisted pair telephone lines usually operate at 57.6 Kbps or, with Digital Subscriber Line (DSL) service, at 512 Kbps or faster. So-called "cable modems," designed for use with TV cable networks, can operate at more than 1.5 Mbps. Fiber optic modems can send and receive data at many Mbps.
The bandwidth of a signal depends on the speed in bps. With some exceptions, the higher the bps number, the greater is the nominal signal bandwidth. (Speed and bandwidth are, however, not the same thing.) Bandwidth is measured in standard frequency units of kHz or MHz.
Data speed used to be specified in terms of baud, which is a measure of the number of times a digital signal changes state in one second. Baud, sometimes called the "baud rate," is almost always a lower figure than bps for a given digital signal because some signal modulation techniques allow more than one data bit to be transmitted per change state.