Stephen,
Here is a link to a Knowledge Base, which contains detailed information about our SH68-68-EP cables:
http://digital.ni.com/public.nsf/websearch/36220E8F02BF21288625686900766E27?OpenDocument
In general our cables are built to preserve signal integrity. Our cables feature individually shielded twisted pair digital lines, seperate digital and analog sections, individually shielded twisted pair analog input lines, individually shielded analog outputs, and a double grounded shield.
Regards,
Ames
Applications Engineering
National Instruments