I want to know how the books in the library make the access control system call the police. I heard that there is a magnetic stripe on the book, but why can't I find it all the time? Is it?
It is pasted on a book, similar to a bar code. Which page or pages appear randomly in a book. It's the same principle as in the supermarket, but it's not easy to see when it's posted on a book. You can read a book page by page, and you will find it naturally.