How do those walk-through scanners in libraries know if you’re taking a book without borrowing it, especially if those books don’t have metal inserts or anything like that?

Question

How does the library borrowing system work? and how come even if there is no obvious metal insert in the book those gates still know when and when not to beep if the book has or hasn’t been borrowed?

In: Technology

Answer 1

We call it tattle tape. A tiny strip that goes in between pages and so unobtrusive you would never know it is there. Of course, what sets off ours might not work at another library depending on the frequency.