Class 3 is class 3 (2 is 2), I don't see any difference between AC and DC in the 725 descriptions.
The place I have seen the fight is class 2/3 in the same pipe with article 300 wiring but the conductors are "separated" with cable jackets. I have seen that one go both ways.
Edit to add
The classic example would be a phone cable. That is a class 3 that is DC (10-48vdc) until it rings, then it is AC (100vac).
Back when we had the "princess" phone (Its little, it's lovely and it lights) there was also a class 2 (10-14VAC) circuit on the black/yelow pair for the light.
I know "phone" used to be out of our hands when this was all Ma Bell but it is certainly there now with 3d party installers.
[This message has been edited by gfretwell (edited 11-16-2006).]
