How Do Library Security Scanners Work?

By Fraser Sherman

A man is checking out books at the library.
i Wavebreakmedia Ltd/Wavebreak Media/Getty Images

For most of the 20th century, accessing your local library was very low tech. You showed a staffer your library card. She took a card out of the back of the book, stamped it with the due-back date and made a record of what you borrowed. Now libraries rely on computers to check out books and stymie book thieves.

Behold the Bar Code

Some libraries use a bar code scanner to track who has which book. When you check out, the scanner fires a beam of red light at the bars on your card, and on each book. The scanner reads the pattern of reflected light, turns it into a digital signal and sends the data to the library computers, recording what you checked out and when it's due back. Some smartphones have apps that record the owner's library card number. However, bar code scanners can't read the pattern off a digital screen, so the library needs a different scanner to work with the apps.

Accessing Technology

The bar code on your card also makes it simpler to access library computers. You either scan your card or type the number on your library card on the computer keyboard. This identifies you as a library member and tracks the time you spend on the computer -- a lot of libraries limit time due to heavy demands. Some libraries issue temporary cards to give visitors or tourists access to the computers.

Books That Vanish

Radio-frequency identification technology goes a step beyond bar codes. To check out a book with an RFID microchip, the librarian places it on a receiver. The receiver sends a signal to the chip which replies with the book's identifying data. RFID chips make it easy for patrons to check out books themselves. The chips also double as a theft-prevention device. Scanners at the library exits detect chips that haven't been deactivated by the receiver and alert the staff.

The Downside

The biggest drawback to libraries going high-tech is often cost. Oregon's Washington County says on its website that setting up an RFID system cost an estimated $1.4 million, though the increased staff efficiency cuts costs every year; Even so, some smaller library systems can't afford it. One Ohio librarian told the "Columbus Dispatch" that despite theft losses, it was more important to use the library budget to add books to the shelves.