Itinerary card. The communication big data itinerary card is provided free of charge to the country's 1.6 billion mobile phone users by China Information and Communications Research Institute and three basic telecommunications companies, China Telecom, China Mobile and China Unicom, using mobile phone signaling data and obtaining it from the base station location of the user's mobile phone. Inquiry service, mobile phone users can use the service to inquire about the information of all the cities that they have visited in the past 14 days. So I know which district in Guangzhou I am coming back from through the epidemic prevention itinerary card.