Alerts can be applied with a parking lot, transport vehicles around the
car, road construction site, the accident scene has obvious protective
warning to avoid accidental damage to property and caused huge
economic losses. Various situations in the complex field of sewer
construction, electrical cable construction site, the road construction
site, the building construction site in construction, there is a clear
warning of protection to avoid accidental access to the property
caused damage and human casualties, is not or lack of warning
protective equipment.