Jasen Betts wrote in a message to Roy J. Tellason:

 JB> Hi Roy.

 JB> 19-Aug-03 20:00:56, Roy J. Tellason wrote to Jasen Betts

 JB>> 4 contacts on the outside of the case, 5 if you count the
 JB>> shell/sheild.

 JB>> I think the 10 way socket goes to 2 USB sockets outside the case.

 RJT> I hadn't realized until the second look that this 10-pin header
 RJT> was for *two* connectors

 JB> That sheild is important too. before I installed someone elses
 JB> scanner i discovered the USB cable would make sparks against the
 JB> computers chassis. it was a Canon but the chinese made plugpack
 JB> looked identical to the HP scanners plug pack (identical plastic
 JB> shell), except for the brand on it I guess there's a slight
 JB> isolation problem there... I didn't try to get a figure on the
 JB> potential there as I didn't have my meter with me but ISTM that
 JB> without the sheild there to earth it something could have goot
 JB> cooked when I plugged the USB cable in...

Seems like a reasonable assumption to me.

I don't know enough about the hardware relating to USB to have any idea of
how robust it would be in terms of overvoltages and whatnot.  Probably not
very much...

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