(56 kilobits per second) The data capacity of a normal single channel digital telephone channel in North America. The figure is derived from the bandwidth of 4 kHz allocated for such a channel and the 16-bit encoding (4000 times 16 = 64000) used to change analogue signals to digital, minus the 8000 bit/s used for signalling and supervision. At the end of 1997 there were two rival modem designs capable of this rate: k56flex and US Robotics' X2. In February 1998 the ITU proposed a 56kbps standard called V.90, which is expected to be formally approved during September 1998.