DE & Time Trial Differences?

What are the differences between a DE and a Time Trial?
I get the feeling that the TT is more stringent in as far as safety equipment and are timed...what about passing regs?
I have done what are called DE's at Laguna Seca, Big and Little Willow and Road America... where my stock 3pt belts are A-OK.
I would love to come out and play at some of the big track events bt it seems that an ss class car is out of luck without 5pts etc.
Just curious
I get the feeling that the TT is more stringent in as far as safety equipment and are timed...what about passing regs?
I have done what are called DE's at Laguna Seca, Big and Little Willow and Road America... where my stock 3pt belts are A-OK.
I would love to come out and play at some of the big track events bt it seems that an ss class car is out of luck without 5pts etc.
Just curious
