(bps, b/s) The unit in which data rate is measured. For example, a modem's data rate is usually measured in kilobits per second. In 1996, the maximum modem speed for use on the PSTN was 33.6 kbps, rising to 56 kbps in 1997. Note that kilo- (k), mega- (M), etc. in data rates denote powers of 1000, not 1024.