Check out Intellon's www site ( <http://www.intellon.com/prod.html) for the
SSC P485 PL Transceiver IC, which
is an intelligent spread spectrum transceiver, similar to RS-485
transceivers.  It can transmit over a.c. or d.c. power lines, twisted pairs
and other communication media, at 9600 baud.  Hope this is of interest to
some of you!

Regards,
Gary Pepper
Ottawa, Ontario, Canada

p.s.  I have no affiliation whatsoever with Intellon.