at the big box stores they have these little thingys that they put on some products

so it will sound an alarm when or if someone tries to leave without paying for it. My question is what is that little thingy anyway, I've cut them apart and all is in there is a piece of tinfoil, how does it work. what makes it not sound an alarm after you pay for it. I just don't understand how all this works.

But I'm not the definitive source on that. I've pulled one apart, and that's what they appear to be.

white things and I don't see anything except the shiny metal piece, so maybe this is a different type as there seems to be no circuit nor antenna, in other words I'm totally confused and I sure don't like it when I am either.

are demagnetized or something at checkout so as not to trigger an alarm when you leave.

The plastic thingy's with barcodes are probably RFID chips. They are not only antitheft devices but track you as you walk through the store, for marketing purposes.

"Do not place credit cards or drivers licenses here".

Which means that flat panel probably generates a low level EMP that fries the circuit but leaves the actual product intact.

Well, it may not be an EMP but something that wipes out a circuit that can also wipe out data on a magnetic strip...

I imagine 90% of that tinfoil is an antennae; the actual circuit in the middle -- once deactivated, the store's front door sensors don't react.

Amusingly, it's possible to buy something at one store, have it deactivated, go through the scanner just fine, then go to another store with the same item, walk through its sensors, and the bloody thing goes off. As that has happened, take my entire response with a grain if not a bucket full of salt.

the alarm was going off anytime anyone got near the door at the Home Depot down the road. The checkout gal says the things broke ya'll just go ahead. So I guess the way to trick fuck the alarm is to ensure it goes off all the time. Kinda like a car alarm in a parking lot. Who pays attention?

Paper's please! :-)

but I've often wondered because the ones I've taken apart has only a piece of shiny metal in them. I think I'll go look and see if I still have one and cut it apart to see if I can see anything other than that piece of shiny metal, a circuit or an antenna

Rather than having a chip that receives a frequency and retransmits at another to set the alarm off, some are simply magnetized, sounding the alarm when the magnetic field is detected. These are usually demagnetized at checkout. I'm not one hundred percent sure this is the case, but it seems to be.

I don't know if they're under other tags as well, they may be.

When my grocery was doing a remodel I saw them installing the sensors by the door and asked what they were for. They told me about using the security tags under the weight/price label on meat products then.

The magnetic strip simply causes changes in the magnetic field of the coils you walk through when you leave the store, causing a change in electrical current in the circuit, and setting off the alarm. That's the old way.

Newer systems use RFID tags - typically a sticker, with a thin foil antenna embedded in it, connected to a microchip the size of a pinhead. When an RFID reader activates the tag, by exposing it to a short range RF field, the radio energy is actually enough to be picked up by the foil antenna, which creates a tiny electrical current that powers up the microchip, which sends a signal back using RF backscatter, containing data like a serial number and the contents of a small amount of memory. Some tags do have a specific flag on them (called an EAS register) for anti-theft purposes that can be activated or deactivated by the cashier so when you walk through the door, if the flag is active, the reader reads that flag and sets off the alarm.

so now I will ask, why can't a would be thief carry a magnet or a demagnetizer with him/her and do the dirty deed before they get to the door. we just recently left the chinamart near here and set the alarm off and had to wait until the somebodies got there to go through our quite full basket and check off everything all the while we were stuck there with people, who some we knew looking at us like wow I wouldn't have ever thought you two would try to steal something. happened to our son and his wife a while back and he was to say the least pissed off about it. they like us are not thieves nor will we, any one of us, buy anything remotely that could be hot under any circumstances. anyways being the tinkerer that I am, always taking things apart to see how they work and all, I was wondering how those things work