Data transmission basics
www.dtr.isy.liu.se/dtr
www.digitaltx.com/dtx/index.htm
www.tml.hut.fi/Opinnot/Kalvot/vemppa295/tsld001.htm
www.satamerica.com/p4.html
www.lascomm.com/fobasics.htm
www.networksthatwork.com/basic3.htm