I purchased a book from the book shop which has a small plastic white strip attached inside the book,upon payment the casher will put the book on a special device mat. If this is not done, when you leave the store the security alam will go off. I opened the plastic strip and found two pcs of slim metal strip of 3 cm length. I am curious what is the " magic " in this metal strip. Perhaps some members may have the same experience. Did any person know the " magic ". Thank you for advice in my question . Regards
- posted
15 years ago