Hirschmann RS20 Reference Manual page 559

Glossary
slows down the rate of data
transmission considerably, but it
ensures accurate transmission.
Xmodem can be implemented either
in software or in hardware. Many
modems, and almost all
communications software packages,
support Xmodem. However, it is
useful only at relatively slow data
transmission speeds (less than
4,800 bps). Enhanced versions of
Xmodem that work at higher
transmission speeds are known as
Ymodem and Zmodem.
CLI L2P
559
Release 7.0 05/2011