Under the existing circuit breaker pilot, trading in a stock pauses across the U.S. equity markets for a five-minute period if the stock experiences a 10 percent change in price over the preceding five minutes.

FORBES: Proposal to Address Extraordinary Market Volatility

Single stock circuit breakers are now in a pilot phase, but there have been glitches.

FORBES: What's This About a Hindenburg Omen?

If approved, the new limit up-limit down mechanism would replace the existing single stock circuit breakers, which were approved on a pilot basis shortly after the market events of May 6, 2010.

FORBES: Proposal to Address Extraordinary Market Volatility