RPI

from The Free On-line Dictionary of Computing (8 July 2008)
Rockwell Protocol Interface
RPI

   (RPI) A cost-cutting feature of some {modems} allowing data
   {compression} and {error correction} (e.g. {ITU-T} {V.42bis},
   {V.42}) to be provided in software instead of hardware.

   Usually an RPI modem comes with RPI-aware software (e.g. the
   low-end RPI models of Supra come with the {COMit} which
   supports RPI, providing {MNP} 2,4,5,7, V.42 and V.42bis).  RPI
   is not supported by many commercial packages nor by current
   releases of popular {shareware} communication programs
   ({Telix} v3.22 and {Telemate} v4.12).  {ProComm Plus} for
   {Windows 2.0} will support RPI.

   Currently {Rockwell} produce two classes of RPI chip set.  The
   original is capable of 2400 bit/s data, 9600 bit/s class
   1-only fax.  The newer one is capable of 14400 bit/s data/fax.
   Currently there are no RPI chipset from Rockwell supporting
   speeds higher than 14400 bit/s.

   (1994-07-01)