It's called a barrier light. Prevent aerial vehicles from hitting the tower crane. In the early years, they used a cable 220 AC light bulb. They use solar lights now. The national standard code stipulates that the tower crane with the tower top higher than 30 meters should be equipped with anti-collision red lights on the top of the tower and the head of the boom. Dysprosium lamps are used for tower cranes. Dysprosium lamp is a high-intensity gas discharge lamp, which is a new type of gas discharge light source with high luminous efficiency (75lm\/w or more), high color dominance (color index 80 or more) and long life. It is a kind of metal halide lamp, which uses the injected dysprosium iodide, thallium iodide, mercury and other substances to emit its unique intensive spectrum, which is very close to the solar spectrum. Thus, the luminous efficiency and color rendering of the lamp are greatly improved.
The red dot above the crane is a safety warning sign. It is usually used to indicate the working status of the crane or to warn people around. Red is a striking color that attracts people's attention and alerts them to the presence and potential dangers of cranes.
This red dot may indicate that the crane is in operation, or warn people not to go near the crane area. In either case, the red dot is meant to keep the workplace safe and prevent accidents. Therefore, when you see the red dot above the crane, please be sure to pay attention to and comply with the relevant safety regulations.