Known previously as V.pcm, the V.90 standard was approved in February 1998, clearing the way for universal compatibility among various 56K modems. V.90 has established a single standard so that all 56K modems will be interoperable and universally compatible.
Interoperability is a key factor that enables different modem brands to connect and communicate.
As a result, the analog modem used to connect a PC to a remote computer or server uses analog communications for a very small part of the link. A 56K modem, however, is different. By dealing only with one analog to digital conversion, higher speed is inherently possible. The jump to 56K modem technology is different than the modem speed increases of the past. There are a number of limitations inherent in the technology and the communications infrastructure which limit the speed of data transmissions across the PSTN network.