A volatile stock market has repeatedly triggered so-called circuit breakers. Here's what they are, and what sets them off.

· *US stocks and US futures have hit multiple circuit breakers that halt trading this week.  *
· *The trading pauses come as coronavirus-induced panic leads to violent market swings. *
· *Here's what the triggers mean, and what sets them off in markets. *
· *Read more on Business Insider. *

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