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

Oh, they have them. You just aren’t seeing them easily, or they’re outright hidden.

There’s a few ways they can mark the books. A common one is a microchip. However, they can also use a sticker (sometimes looks like a circuit) or even slide strips into the spine or under a book jacket without them being visible. These then can respond to radio or magnetic signals from the scanners, and they have some kind of code read by this device that says what the book is. The strip may also be able to be programmed to say if it is checked out or not; otherwise, the code will need to be compared to the code in the system and the status listed there. If the code says it isn’t checked out, then it sends an alert.