Hello,
An excellent response to this questions has been posted on another discussion forum thread:
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=506500000008000000D4C70000&UCATEGORY_0=_30_%24_12_&UCATEGORY_S=0
Have a great day!
Ken S.
National Instruments