Simply put, the so-called fuse mechanism means that when the stock market falls to a certain extent, the market automatically stops trading for a period of time, which may be a few minutes, or the whole day trading may be terminated.

the main purpose of this is to prevent the panic from spreading further and bring greater impact to the market.

the reason why the United States introduced the fuse mechanism was the "Black Monday" in 1987.

on October 19th, 1987, the Dow plummeted by 58.32 points, or 22.6%. Three months later, the fuse mechanism was introduced in February 1988, and it was first implemented in October.

At present, there are fuse mechanisms in the United States during US trading hours and non-US trading hours, and even some stocks.

except for stock index futures in non-U.S. trading hours, there is only a fuse mechanism for decline in U.S. trading hours.

during trading hours in the United States, the fuse mechanism can be divided into three levels.

(1) the primary market is blown, which means that the market falls by 7%

(2) the secondary market is blown, which means that the market falls by 13%

(3) the tertiary market is blown, which means that the market falls by 2%

. Today, the S&P 5 index falls by 7%, triggering the first layer of blown.