CVSC http://www.google.com/patents?vid=USPAT5891012&id=sqoWAAAAEBAJ&dq=patent:5891012 http://www.google.com/patents?vid=USPAT6149578&id=jz4FAAAAEBAJ&dq=patent:6149578 http://www.google.com/patents?vid=USPAT6190304&id=xjgFAAAAEBAJ&dq=patent:6190304 http://www.google.com/patents?vid=USPAT6228018&id=kN0FAAAAEBAJ&dq=patent:6228018