Truncated match.
PICList
Thread
'anti-theft sticker'
1997\12\01@160151
by
Jarek Pawlega
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.
1997\12\01@162925
by
John Shreffler
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}
1997\12\01@163001
by
Andrew Mayo
|
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_OUTjpawlegaTakeThisOuT
PERLE.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.
>
1997\12\01@165333
by
Martin R. Green
|
On Tue, 2 Dec 1997 10:25:07 +1300, Andrew Mayo <andrew
KILLspamGEAC.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!!!
1997\12\01@170611
by
Alberto Smulders
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_OUT
TakeThisOuTitacom.com.py
1997\12\01@221327
by
Mroczkowski
<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
mrgreen
spam_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
1997\12\02@084627
by
David Anderson
|
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}
1997\12\02@113253
by
John Payson
> 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.
1997\12\02@154403
by
Wim E. van Bemmel
|
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@bemspanKILLspam
xs4all.nl
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