Universal Videohub Editing Interface

I just need some clarification on the Universal Videohub Editing Interface. What are the "reference" connections for? Sync? SDI?

Thanks
Sean

Reference in takes an analog Black signal, like from the Blackmagic Sync Generator (or similar product). This will allow for vertical interval switching. I don't use a router as a switcher, so I never hook this up in my installs. A TV station using the Videohub that is automated might do this, but not in a production or post production enviornment.

Bob Zelin