question on trading collars and curbs

what exactly are they and what do they mean? i looked it up but its a bit vague.

 

This is what happens when the NYSE invokes.

http://www.nyse.com/press/circuit_breakers.html

The CME has a different set of criteria for S&P futures moves as well.

Basically, they stop allowing automated program trading until the index moves back above the limit down territory.

If S&P futures are down limit, they stop trading for 15 minutes, then reopen, if they are down limit again, the stop again.

Don