Because in order to prevent books from being lost, the library now uses electromagnetic induction detection system. He uses the detection coil to detect the medium to realize automatic alarm, including high frequency and low frequency, as well as an intelligent detector integrating high frequency and low frequency. The principle of the detection system is to use the high permeability of the magnetic stripe to detect the signal and drive the alarm under the action of a specific closed-loop electromagnetic field. Generally, the object of detection is only amorphous items in books, and no alarm will be given to other objects. But maybe some machine parts of your computer also have high permeability, which leads to false positives. However, this is usually not the case. Generally speaking, the induction channel has a specific setting and will not give an alarm. If you really keep calling the police, but others don't, you can discuss it with the librarian or explain the situation to him. If you give full consideration to the interests of readers, you are looking up information and have not violated the regulations of the library. To a certain extent, librarians should be reasonable.