> Use infrasound to detect an 'end of track' tone in the MP3 file.
> It won't be audible unless you have a subwoofer, and doesn't
> need to be loud to be detected. (NE567 works well, but you could
> do it with a PIC with A/D and low pass filter using one of the
> 'tone detect' algorithms.).

This is a great idea!  But rather than add the kill tone to each MP3, just 
create a short file containing the kill tone and place it between each pair 
of tracks.

Or, maybe you can get the MP3 player to stop on its own by putting an 
illegally coded file in.

Bob Ammermamn
RAm Systems

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