The fact that the code shows up even when you're passing by means that the system is recording the short time you're there, and it's just a matter of system setup.

The trip code is the communication big data trip card a code is also equivalent to the health code, is by the China Academy of Information and Communication Technology, China Telecom, China Mobile, China Unicom three basic telecommunication enterprises to use the data received by the cell phone, through the user cell phone is located in the location of the base station to obtain, for the country's 1.6 billion cell phone users free query service, cell phone users can be used through the service, to query the first 14 days of my visit to all cities and towns information.

The changes to the travel code are introduced as follows:

The Travel Card APP2.0 adds a close contact reminder function based on Bluetooth Low Energy Protocol (BLE) on the basis of the travel query, so that if a stranger who has had close contact with you is diagnosed as a confirmed/probable patient of New Crown Pneumonia, the use of the service will remind you to pay attention to the isolation observation in a more timely manner.

The Chengdu trip card turns red only as a travel reminder, not associated with health status, but only for the names of cities and regions that contain medium and high risk areas marked in red. Please follow the local joint prevention and control mechanism for specific control policies.

Reference: People's Daily Online - Plan your trip in advance, people entering Beijing need to verify their trips in the last 14 days to get a green code