http://www.google.com/patents?id=sPsEAAAAEBAJ&pg=PA1&lpg=PA1&dq=US+Patent+6135047&source=bl&ots=Jkn5Dpfi6G&sig=IucRuQMNitGFqeyAOPdM6Io0L-A&hl=en&ei=xISdStnpMpGe8Qb72ZCpAw&sa=X&oi=book_result&ct=result&resnum=7#v=onepage&q=US%20Patent%206135047&f=f...