When you drive to a foreign country by yourself, the trip code will also be displayed because it is based on your cell phone signal and positioning.

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