56 Kbps modem technology (1)
asymmetrical : 56 Kbps (downstream); 33.6 Kbps (upstream)
ITU V.90 - standard covering 56 Kbps modems (will be probably ratified in September 1998). At the moment there are 2 proprietary and incompatible specifications: X2, developed by US Robotics, and K56flex by Lucent and Rockwell Semiconductors Systems.
about 70% of the 56K modems use K56flex technology. Recently 28 data communications and computer vendors created Open 56K Forum which intends to push K56flex technology as new standard.