What about what they gave us in 2000 it was a pneumatic cylinder that had a magnet or somthing in in it that would slide around the cylinder. Mmm bad explination if you look in Ed Spark's Cad library under archive you will find it there. This more than likely is what they are talking about.
http://www.firstcadlibrary.com/pages/archive.asp Scroll down it looks like this :
