Tattle-Tape

The tape consists of a magnetic metal strip embedded in a strip of thick, clear adhesive tape.

When the magnetic strip in the tape is sensitized, an alarm will sound when the item passes through a special gate, typically near the exit.

When the book is returned, the tape is re-sensitized by library staff.

Tattle-Tape was designed by 3M and was first used at the Saint Paul Public Library in 1970.

[1] In 2015, Bibliotheca purchased 3M's Library Systems business and acquired the assets of its remaining global business.

A box of Tattle-Tapes still on their protective plastic strips, with some resting on top of a magnet block used for 'desensitizing' them, allowing a book to be taken out of the library without alarms.