Want to know where the siren sounded in Shenzhen today came from?

Did Shenzhen pull it off? Shanghai is scheduled to sound an air defense alert in five districts at 10 noon on the 15th.

Alarms were first placed on the roofs of some public buildings, such as government agencies/cinema/bus stations. Later, as more and more high-rise buildings became available, they were also placed on the roofs of some commercial buildings. It's an electric horn, dumbbell-shaped, about 30 cm in diameter and 50 cm long. There is usually an iron shelf underneath. There is also a part that looks like an inverted hat, like a UFO, wide at the top and narrow at the bottom. Urban distribution is generally evenly distributed based on distance. In the suburbs, they are usually at the commanding heights of market towns.