56K modems are analog modems capable of speeds near 56 kbit/s when connecting to a service that has a digital connection to the phone network.
It is important to note that this technique cannot be used between two 56K modems and that when two 56K modems connect they will revert to slower standard analog methods.
At the end of 1997 there were two rival modem designs using this technique: k56flex and US Robotics' X2. In February 1998 the ITU proposed a 56 kbit/s standard called V.90, which was formally approved during September 1998 .
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