Why does the exit alarm sound even though I do not have any library materials?

The security system is the same type used in many department stores, and sometimes manufacturers put tags in places inside backpacks or clothing where the stores cannot eaily remove them; if the alarm sounds, please empty your bag and remove your coat, following the instructions of the staff member at the desk. If nothing belonging to the library is found, you should look carefully to see whether you can find a security tag somewhere in your belongings.