Post by thread:anti-theft sticker

I went to the bookstore, during my lunch break today and I bought a book. There was a plastic sticker on the book, with a bar-code on it and two isolated strips of metal inside the sticker. As soon as the bar-code is scanned the anti-theft gate doesn't 'care' the sticker, assuming, the good was paid. Otherwise, carrying the book through the gate will cause activating the alarm system. We all used to see them, almost everywhere. Does anyone of you, gentlemen, know, how this system is called, how the sticker 'works' ? I guess, it might be some kind of resonant / absorbing device, those two strips of metal are acting like but I can't believe it is addressable 'by sticker'. It should require very high accuracy. Regards, Jarek p.s. Of course, I'm not going to still anything. Except some knowledge.

part 0 1522 bytes In some systems there is a diode between the metal foil patterns which act as an antenna to pick up 2 GHz radiation, and reradiate back a lot of harmonics, which in turn are picked up by the alarm receiver. The device is defanged by applying a pulse that destroys the diode. But I have also disected some tags that are slipped into the binding of library books, that seem to be only a couple of parallel foil strips, no diode. I can't imagine how they work, but would also be interested if anyone has the answer. John {Original Message removed}

It is a resonant circuit, which is triggered by a transmitter in the doorway. By passing a strong magnetic field over the device, it can be deactivated - I am not quite sure how this works but I think what happens is that part of the strip is ferromagnetic. If it is magnetised, it affects the resonant circuit, either by changing the frequency or introducing harmonic distortion. Some variant devices use (I think) a small low-signal diode which is destroyed by an electromagnetic pulse - until this is done passing the circuit through the door will generate a strong second harmonic signal which will trigger the alarm. {Quote hidden}> ---------- > From: Jarek Pawlega[SMTP:spam_OUTjpawlegaTakeThisOuTPERLE.COM] > Reply To: pic microcontroller discussion list > Sent: Tuesday, December 02, 1997 8:46 AM > To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU > Subject: anti-theft sticker > > I went to the bookstore, during my lunch break today > and I bought a book. There was a plastic sticker on the > book, with a bar-code on it and two isolated strips > of metal inside the sticker. > > As soon as the bar-code is scanned the anti-theft > gate doesn't 'care' the sticker, assuming, the good was > paid. Otherwise, carrying the book through the gate will cause > activating the alarm system. > > We all used to see them, almost everywhere. > > Does anyone of you, gentlemen, know, how this > system is called, how the sticker 'works' ? > > I guess, it might be some kind of resonant / absorbing > device, those two strips of metal are acting like > but I can't believe it is addressable 'by sticker'. > It should require very high accuracy. > > > Regards, > Jarek > > > p.s. > Of course, I'm not going to still anything. Except some knowledge. >

On Tue, 2 Dec 1997 10:25:07 +1300, Andrew Mayo <andrewKILLspamGEAC.CO.NZ> wrote: >It is a resonant circuit, which is triggered by a transmitter in the >doorway. By passing a strong magnetic field over the device, it can be >deactivated - I am not quite sure how this works but I think what >happens is that part of the strip is ferromagnetic. If it is magnetised, >it affects the resonant circuit, either by changing the frequency or >introducing harmonic distortion. > I have dissected some of these and found a small printed metallic coil, which I presume is part of that resonant circuit. > >Some variant devices use (I think) a small low-signal diode which is >destroyed by an electromagnetic pulse - until this is done passing the >circuit through the door will generate a strong second harmonic signal >which will trigger the alarm. > Gee Whiz - does this mean I could defeat these things by carrying a small EMF pulse generator, such as an electric butane BBQ starter wand? ;-) CIAO - Martin. Martin R. Green .....mrgreenKILLspam.....NOSPAMbigfoot.com To reply, remove the NOSPAM from the return address. Stamp out SPAM everywhere!!!

Jarek, Take a look at http://patent.womplex.ibm.com/ and see patents (among about 100 others) 5,300,922 - 5,574,431 - 4,413,254 - 4,622,542 - 3,983,552 - 4,074,249 - 3,820,104 - 4,063,229 - 4,993,245 - 5,572,191 - 5,008,649 - 3,895,368 - 5,510,770 - 5,300,922....... and I think you'll know everything about how the whole security-tag stuff works.... Albert Smulders InSAD - Encarnaci—n, Paraguay EraseMEinsadspam_OUTTakeThisOuTitacom.com.py

<snipsnipsnip> Gee Whiz - does this mean I could defeat these things by carrying a small EMF pulse generator, such as an electric butane BBQ starter wand? ;-) CIAO - Martin. Martin R. Green mrgreenspam_OUTNOSPAMbigfoot.com To reply, remove the NOSPAM from the return address. Stamp out SPAM everywhere!!! ================= Actually, they are deactivated by a pulse that "burns them open"...something a B-B-Q starter would be hard pressed to produce;^)) Simply covering the patch with a piece of aluminum foil will render it inoperative. -Cheers, Hank

There are three types of theft detections systems I'm aware of. The kind that requires a sticker and is a resonant circuit is made by a company called CheckPoint. The sticker has a metal foil resonant circuit tuned to a specific frequency. The detectors are tuned to a specific frequency, so little else will set them off. I worked in a library that used the checkpoint system. We had special due date cards that went in the pockets to "deactivate" the sticker. The cards themselves had a sheet of foil embedded inside. You'll see the checkpoint sticker most often in the pocket of a book. In commercial applications, it may be disguised as a UPC. A tear in the circuit is usually enough to deactivate it (razor or simply rip some of the sticker off). The other major system in use, especially in libraries, is the 3M Tattletape. These are thin strips about 3-5" long and about 1/8" wide. They are magnetically deactivated, so a strong magnet will detune them. Of course, so will pulling out the Tattletape. The most common location for tattletape is in the spine, so the book can be slid along its spine in the desensitizer. The tattletape is also used a lot in cd stores. The third I've only seen in retail. It's a small plastic strip about 1 1/2" long, 1/2" wide and 1/16" high. It's also magnetically desensitized, based on the desensitizer's I've seen. Ripping the sticker off seems to be the only safe approach. {Original Message removed}

> The third I've only seen in retail. It's a small plastic strip about 1 1/2" > long, 1/2" wide and 1/16" high. It's also magnetically desensitized, based > on the desensitizer's I've seen. Ripping the sticker off seems to be the > only safe approach. Isn't a somewhat safer approach to hand the item to the person sitting near a machine with lots of buttons on top and a money drawer underneath? Prefer- ably with a bribe in an amount typically marked on the item in question? I have found this approach to be 99.9% reliable in ensuring that the alarm does not go off, and I have also found the store personnel to be quite friendly and apologetic on those occasions when the alarm has tripped. While your approach might have similar reliability at avoiding the alarms, I doubt the personnel would be as friendly on those occasions when the alarm sounds.

Hear! Hear! John Payson wrote: {Quote hidden}> > The third I've only seen in retail. It's a small plastic strip about 1 1/2" > > long, 1/2" wide and 1/16" high. It's also magnetically desensitized, based > > on the desensitizer's I've seen. Ripping the sticker off seems to be the > > only safe approach. > > Isn't a somewhat safer approach to hand the item to the person sitting near > a machine with lots of buttons on top and a money drawer underneath? Prefer- > ably with a bribe in an amount typically marked on the item in question? I > have found this approach to be 99.9% reliable in ensuring that the alarm does > not go off, and I have also found the store personnel to be quite friendly and > apologetic on those occasions when the alarm has tripped. > > While your approach might have similar reliability at avoiding the alarms, I > doubt the personnel would be as friendly on those occasions when the alarm > sounds. -- Regards, Wim ------------------------------------------------ Wim van Bemmel, Singel 213 3311 KR Dordrecht Netherlands @spam@bemspanKILLspamxs4all.nl ... Life is about Interfacing ..... ------------------------------------------------