Hello;
There are some good links at NI home page regarding that particular cable. This is one good example: http://ae.natinst.com/operations/ae/public.nsf/fca7838c4500dc10862567a100753500/36220e8f02bf21288625686900766e27?OpenDocument. But, you can find extra information by typing sh68-68-ep at the search field.
Hope this helps.
Filipe