NEC POWERMATE ES 5200 Service Manual page 290

X
X2 technology
A technology developed by U.S. Robotics (now 3Com) for delivering data rates up
to 56 Kbps over plain old telephone service (POTS). It was long believed that the
maximum data transmission rate over copper telephone wires was 33.6 Kbps, but
X2 achieves higher rates by taking advantage of the fact that most phone switching
stations are connected by high-speed digital lines. X2 bypasses the normal digital-
to-analog conversion and sends the digital data over the telephone wires directly to
a modem where it is decoded.
Glossary 17