The following is a tabulation of some prior art that presently appears relevant:
U.S. patentsPat.  No. Kind CodeIssue DatePatentee6,571,548B1Jun.  03, 2003Bronicki et al6,857,268B2Feb.  22, 2005Stinger et al7,096,665B2Aug.  29, 2006Stinger et al7,942,001B2May 17, 2011Radcliff et al
U.S. patent application PublicationsPublication NumberKind CodePublication DateApplicant2008/0289313A1Nov.  27, 2008Batscha et al2010/0242479A1Sep.  30, 2010Ast et al2010/0071368A1Mar.  25, 2010Kaplan et al2010/0263380A1Oct.  21, 2010Biederman et al