None of the others in town have these, thought it was unusual enough to share
some models use a wire in the ground that emits a low frequency radio signal… which can be also be transmitted by the speaker in a phone by simply playing these mp3 files: https://www.tmplab.org/2008/06/18/consumer-b-gone/ (!)
It’s absolutely insane that a speaker coil works as an antenna in this case, but perhaps even more insane that the signal survives mp3 compression.
It has to cover a parking lot full of radio signals from cars. They’re probably just listening for “close enough”.
It’s more likely a buried loop antenna, like an invisible fence.
Why is that insane? The entire point of an mp3 file is to be able to reproduce signals with reasonable accuracy. Seems like the signal has a frequency of around 8khz, which is very much in the range of human hearing and should be preserved by an mp3.
No, the point of MP3 is to compress audio in a lossy manner while minimizing the introduction of artifacts detectable by human hearing using psychoacoustic analysis. The coincidence that the necessary parasitic EM signal induced by speaker drivers happens to be created by a signal that doesn’t suffer degradation by a relatively specific lossy compression method is remarkable.
Right, but artifacts in the ~8khz range will be detectable by human hearing. mp3s are going to be perfectly acceptable for many sounds in that frequency range… The fact that this works is evidence of that.
Plus, you know what else is lossy? Radio. If the signal is that fragile there’s a good chance the locking mechanism wouldn’t work in the first place.
Go actually read about MP3 compression before you continue misusing the term “lossy.”
It’s just going to be pulses of an 8khz signal. Why would an MP3 not encode this just fine?
Like I said before, the coincidence is what’s remarkable.
Can you imagine what would happen if someone went into a crowded store with a device playing this. A short loop through the isles and til queues would wreak havoc.
Sounds like a basis for a fantastic prank.
Those things have been around for a long time.
I remember them being introduced at least 15 years ago. My manager at the time would wait and laugh at people trying to take them past the parking lot. She was a really miserable person.
I wouldn’t be surprised if they don’t even work anymore just because of how long they’ve been around.
I’ve never bothered to try it recently though.
They likely get repaired/replaced when they die. When the batteries die the brake locks shut so you can’t move it. No idea how long they last though
Many grocery stores in my area have these wheel locks. If I recall from college, if you took the cart out of the parking lot by carrying it over the plant beds, the lock would not engage.
These most likely lock from a small electric loop around the lot triggering an internal magnet, so y’all found a gap in the loop.
Nice hacking.
You can just lift the wheel about a foot off of the ground when passing the loop that engages the lock. Much easier.
The safeway near my apartment is so ghetto the wheels lock as soon as you leave the store exit. You have to take everything in one trip or wait for your car to pull around to load.
I’m pretty stubborn. I’d probably just drag it across the parking lot like a neanderthal and let the asphalt grind flat spots onto the wheels.
The ones I’ve seen usually only lock one wheel, maybe two on a side. So you can wheelie the carts just fine.
Half the carts I’ve ever used have a busted wheel anyway lol.
I’d go one step further and take the cart, for spite
Even better of you can figure out how to grind the asphalt away with the wheels. Make it reeeeeeally annoying for them.
Must be working. I haven’t seen a cart on cinder blocks in a while.
Pretty much every store in my city has these, didn’t realize they weren’t a thing everywhere.
It’s a litmus test for what type of place you live in. I guess you just found out where yours lands.
Whole thread freaking me out. This is a thing some find normal?!
And lemmy be like, “Fuck cars! Build walkable cities! Live like rats in a cage!”
Uh. No thanks. I’ll stick to the bleeding edge of town, thanks.
What does this have to do with walkable cities?
It’s an anti-theft mechanism to keep people from stealing carts, generally to prevent homeless from taking them.
I don’t agree with it, because the hostility toward homeless people these days is disgusting, but that’s how it is.
LOL, I went a little wide of my point. And my point was, this is the kinda crap you see in densely populated environments. Having experienced the city and country, I’ll take the country all day long. Mammals were not meant to live in packed populations.
Found out the hard way breeding rats in college. Long story, but they had 6 litters one Sunday morning. By Tuesday, those babies were all eaten, no trace. tl;dr: You pack people together, you get bad behavior.
And I hadn’t seen it as an anti-homeless thing! That idea has meat on the bones. Yet another case of American’s treating the symptoms and not the disease. Wasn’t it Chruchill who said, “You can count on Americans to do the right thing, after they’ve exhausted every other possibility.”?
Keep going! I’ve almost got bingo!
Bubbles would be really disappointed
The cart boy would easily find a solution to that weak level of protection. Couple of furniture dollies under a cart instantly restores the rollability and then he could disassemble the wheels back at the shed
If places where I am in the UK don’t have this, they have a coin return on them.
25¢ for a shopping cart is a pretty good deal if you think about it
And if they are like the US Aldi locations, the coin is in the cart. So you even get to take the money with you.
they can’t even charge you with theft because you still technically paid for it
(at least in poland) people usually just leave their coins in the carts, I’ve never had to put my own coin in there
Just more proof of how stingy we are here in England. But if I worked at a supermarket and people did this, I’d just put away the carts and pocket the cash everyday.
If they don’t, they’ll be fishing them out of the canal.
Still see them in back streets all the time
for the small price of a hex head wrench, you too can be the owner of a proud new Walmart shopping cart…. I wonder if walmart sells replacement wheels.
Steal another for spare parts
these are pretty common at supercenters in Chicagoland
There is a walmart locally that has these or used to have them. Theirs were easy enough to disable.
I’ve only ever seen these in malls so you don’t take the carts to other places in the mall. Do they really use these for carts going out to the parking lot too? How’re you supposed to get your groceries out of the store?
My local Kroger has these, the perimeter extends all around the parking lot.
That makes more sense. Prevents them from (easily) leaving the property
I’ve only seen these in action by accident. Happened to me when I tried to go around a planter to reach the eating area at a Whole Foods. Apparently that was beyond the perimeter and I got stuck.
I saw one just last week lock up right at the door of Safeway when a lady was trying to go out to her car (it’s not supposed to block you from exiting the store). She was stuck in the door, cart half outside.
But people who actually do want to take the carts away know exactly how to avoid the mechanism.
We’ve had these in the UK for a long time, mainly to stop people carting shopping home using the trolley and then abandoning it.
Was I the only one who thought the wheel was laying on the ground?
Yes. You are the only one.
Do you know how it works? Doesn’t seem to be electronic or so… Perhaps mechanical magnet based or so
There’s a talk at DEFCON on YouTube about hacking them. Great way to see how it works.
Probably an electrical fence type deal. When the signal gets too weak the pins pop out to prevent the wheel from rotating. Didn’t park near the edge of the property to test it lol
But what powers the wheels? Charged by spinning? What happens if they don’t get used long and the wheel dies.
By spinning yes, they operate mostly passively and therefore last a long time, including by having terrible security to save battery life.
