Clicking on the Link below
will take you to a very informative
Dualmode Power Point Presentation
by MIT Graduate Bruce McHenry.
The file is just over 5.3 MB so,
even with broadband, it will take time to load.
Your patience will be rewarded, however.
http://stuckintraffic.org/dualmode/PPPresentation/tabid/121/Default.aspx