A micro signal can only apply for one health code. A person applying for a health code must be bound with relevant real-name information, so only one micro-signal can be applied after the real name, so a person cannot apply for two health codes. The "health code" is a personal two-dimensional code that can be generated by citizens or rework workers after self-declaration and background audit on the Internet. As an electronic document for personal entry and exit in the region, the QR code is declared to be universal in the whole city at one time.