Ok, We’ve all seen them, the little white strips on the inside of every CD you buy, or DVD, or any form of media. After my curious mind wondered exactly what they were, I investigated and found that they are magnetic strips. When magnetized, the alarms can sense them and put out an alarm. So before you leave the store they must be demagnetized.
This is where my question comes in. How? I ask this in hopes of getting answers to several smaller questions, such as:
Having only lightly dabbled with magnets, and never having studied them, I have no idea how demagnetization works. How is it done? Whate takes place when it is done?
I was told that the demagnetization takes place when the CD is wiped across a black mat type thing on the counter. I was also told this was a magnet. If so, how are VHS tapes not erased when wiped across it? If not, what is it?
Do CDs suffer data loss from exposure to a magnet? If so, how can they sit on top of a magnetized tag for weeks or even months and not get erased?
Lastly, and absolutely the least seriously, is it possible to remagnetize the strip and stick it to my friend and laugh as he cannot figure out why he sets off alarms?
Thanks in advance for your help. I’m a curious mind, and things like this bug me.
Ah, Ok. What about VHS though? I thought VHS was erased by magnets, yet they use the strips on them.
Nitroglycerine: Yes, sure could be. Go through all your old CDs, remagnetizing the strips, and then gain access to a friends dresser, applying a strip to the inside waistband of each pair of his pants. Assuming he doesn’t notice, your in for some fun. Even if you can’t be there, your bound to hear stories of his trip to the mall, where the alarms went crazy on him.
There are several types of those anti-theft strips, they aren’t all magnetic. Some of them are designed to resonate when passed between those gates at the doors, sounding the alarm. Notice at Blockbuster that they hand the tapes to you around that gate, rather than doing anything to deactivate the strip.
VHS tapes will be erased by some demagnetizing equipment if the exposure is long enough, much like credit cards will be demagnetized if left sitting on the pad.
As far as sticking tags on your friend, go for it. As someone who worked in retail for a while, it was great entertainment.
Right, I know, but I’ve seen the magnetic variation on VHS tapes at places that use the black pad. They rub the tape, and hand it to you, is the magnetic charge just not very strong?
Yes. Frequently, when dealing with magnetic-sensitive merchandise at my former place of employment (coughbigyellowtagcough), we would use a different system which used a handheld demagnetizer and key combo unit to unlock and demagnetize a product.
I really have no idea. Your best bet would be to find a strip of them in the store during stocking times.
I’m not sure on the specifics, but I believe it’s a little more involved than that.
erm, I’d tell you how to get around that, but that wouldn’t really be appropriate here, I suppose. I guess this method only works if your friend is with you.
My son set off the alarms at Wal-Mart the other day with one. He happened to have in his pocket the UPC code for an old CD-RW rebate that he’d cut off the box at home, meaning to get the rebate deal all together and mail it on the way home from Wal-Mart. So the UPC code happened to have the anti-theft strip on it, and it set off the Wal-Mart alarm.
If you learn how to re-activate the strip, don’t waste it on your friend. Stick it on a shopping cart so the fun can continue for days (perhaps weeks) to come.
Things are usually demagnetized by putting them in an alternating magnetic field that is gradually reduced to zero, or at least a miniscule strength. An alternative way is to have a constant magnetic field in which you place the object which you then move away. This also gradually reduces the field around the object and demagnetizes it.
There’s a very good article about anti-theft gadgetry at HowStuffWorks.com: How Anti-shoplifting Devices Work.
There are several kinds of ‘electromagnetic devices’, some which use magnetics, and can be re-activated (used a lot in libraries etc), and some that rely on electric fields only, and cannot be re-activated.
Answering that would basically be telling people how to steal, and wouldn’t be appropriate here.
The most common type in use uses two small strips of soft steel magnetized in specific orientations and to a specific level (details are on the How Stuff Works site posted above). As such, it would be very difficult for the average Joe to reactivate them.
Which is deactivated. The mods take a very, very dim view of anyone attempting to solicit information to commit crimes with, so I’d watch your phrasing/requests.
Meh, I can understand, but at the same time that’s stupid. That coming from someone as anti-censorship as myself, shouldn’t be offensive, however.
Civil Defense: My AIM name is Kaleckt999 (Don’t forget the k, alot of people do) and my email is NagelJ@maplenet.sparcc.org if you feel like contacting me. Really, I’m just curious. And since the rules here seem to be so strict…
Q.E.D. I’m not looking for info on how to steal. I can get a CD out of it’s locking case in three seconds flat with a simple paper clip, it is not hard. With a little seclusion, I can even remove the strip from inside the CD case in about 5 seconds. Also not hard. I’m asking solely because I’m curious, but I can understand your position.
