Tattle Tapes (those little metal anti-shoplifting thingies)

Tattle Tapes. In library book bindings and glued to CD’s, in expensive razor blade boxes and stuck to your knees (well, maybe not, couldn’t think of anything that rhymes with CD’s).

Anyway, anybody know what the scientific principals behind these thingies is? I suspect it’s something magnetic involving those Star Trek sensor gates at the doors, but in that case why wouldn’t they screw up watches and pacemakers and stuff?

Anybody got the scoop? I promise it’s purely curiosity.

Does this help?

From “How Do Radio Frequency EAS Systems Work?

That looks like a great site, Alphagene, but I think the OP was talking about the EM system From its explanation at that site:

I was just about to go looking for a site such as this, to explain those EM systems. Thanks!