> >He is using the ac as timebase.
>
> Duh.  Guess I could have figured that out for myself... :)

I think your idea still makes sense, Dave.  You have to have the rectifiers
and cap someplace.  It might as well not be on the rotating board.  I don't
think it would be hard to superimpose a serial bit stream on the power
connection.  This could be fed straight into the UART after detection, using
the slowest possible baud rate.  Timing information can be transmitted as
data, and only needs to be communicated every second.


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