[...] because
USB is
 one-way 
 Since when? 
 
I think David is referring to its polled nature.
--
------------------------------------ personal: 
http://www.cameronkaiser.com/ --
  Cameron Kaiser * Floodgap Systems * 
www.floodgap.com * ckaiser at 
floodgap.com
-- "I'd love to go out with you, but I'm joining my split ends
individually." -