Wi-Fi Cards Can Now Detect Microwave Ovens 124
An anonymous reader writes "Researchers at UW Madison have used regular WiFi cards to detect non-WiFi interference sources like microwave ovens, Bluetooth devices, cordless phones, Xbox controllers and video cameras. They call their software Airshark. Current products like Wispy, Spectrum Expert are expensive and need extra hardware, whereas Airshark is a software-only solution that can directly work on the Wi-Fi cards on your laptops and APs. This also paves way several interesting applications. For example, your WiFi network will not be affected anymore just because your neighbor switched on a microwave oven or a cordless phone — the newer WiFi APs will be able to switch the channels and adapt to the interference accordingly."
You must live in the boonies (Score:1)
If you live in a city or in the suburbs, you can see LOTS of WiFi access points already, so switching to a different frequency won't get you to an interference free channel! Maybe you'll get to a little less populated one, but not interference free!
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My microwave is always running off. This should make it easier for me to find it.
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Down here in NC folks have several good solutions to the beer problem, including making their own (which is way, way better than the beer you can get in any gas station in the boonies unless for you US corporate beer is the epitome of corn-flavored goodness) or saying screw the beer and turning their malted corn directly into an untempered distilled spirit, made (as you say) in relative seclusion. I can only g
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Or use 5 or 5.8ghz. Even if there are tons of devices, it has many times more spectrum than the 802.11b/g band.
What's the deal with 802.11n and the 5 GHz band? I've seen a lot of N equipment that only seems to support the 2.4 GHz band- I'm guessing because it's cheaper to only have one radio?- so is is the case that N equipment doesn't *have* to support 5 GHz? (*)
At any rate, it sounds like buying 5 GHz-supporting N equipment would be worth the extra money. I made sure my first router and card (circa 2005) supported 802.11a even though it cost more because I suspected congestion might become a problem and the less-p
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Yup, cheapo 802.11n stuff doesn't support 5GHz. The only reason I'm still running 2.4GHz is my Android smartphone... stupid cheapo Broadcom BCM4329 doesn't support 5GHz.
At least all my Thinkpads support 5GHz and the router's dual band...
I can definitely recommend going with 5GHz if you don't need all too much range (through walls and such) and the airwaves around 2.4GHz are crowded in your neighborhood.
Look at this crap... my neighborhood at 2.4GHz: http://dl.dropbox.com/u/7086491/pictures/2.4ghz.PNG [dropbox.com]
And 5GH
If only all wifi devices could work cooperatively (Score:5, Interesting)
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The technology allows for this already. However, the security and privacy implications are big. Not to mention bandwidth limitations. And switching capability. And routing tables. And ARP tables. And those are the problems I though about while typing this. I'm sure there are several others.
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You are talking about point to point encryption. Yes, it would be possible, assuming you are able to establish encrypted point to point connections to all services you connect to. Or you can setup a VPN to a "relay" server. The first is simply not a reality at this point, and the second is something most people wouldn't know how to do.
Privacy would still be a problem, because anything up to Layer 3 would not be encrypted in the scenario you propose. Depending on how it is implemented, even Layer 4 would not
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It's call mesh networking. If everyone did it, we wouldn't need telcos (or ISPs) so much.
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In this ideal world of yours, what incentive is there for ISPs to maintain their networks, as you have effectively cut them out of the loop?
You do realize that you would need a backbone SOMEWHERE unless you wanted horrific latency, for example to get traffic from coast to coast?
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Yes, which is why I added "so much".
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Fucking corporate asslicker idiot.
Oh yes, I see. Clearly it is unacceptable to have most of the work I do, as well as most of my clients, rely on sub-1000ms latency getting to the internet.
Honestly, who do you know who would put up with 1second skype latency, or 25 seconds to load any modern webpage (which will ping several domains, as well as do AJAXy requests, all incurring massive latency on a mesh network)? Do you have any idea just how bad the internet would be if everything you do incurred large fractions of a second in latency? Do
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Well, it's not just that, it's that the devices are designed to give the most range possible without going with a unidirectional antenna. And the problem is that it worked fine when the 802.11b devices were first rolling out because few people had them, but as they've gotten to be common, you then have to deal with a dozen WAP competing for scarce spectrum.
And all is well and good if you have a large property, but if you're in an apartment and just need something that's fast and can let you move from the de
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say 15' away, having a device cranking out enough power to go 200' is way too much power
The WiFi routers I've seen have a setup were one can adjust the output power. Of course, almost noone sets it to something sensible, which means my neighbour's signals a stronger than my own in parts of the apartment (on the other hand, that same inability to configure WiFi means they all fight around the channels 1-4, so I can avoid them).
Routers should have an automatic power adjustment for the devices it has connected. Is this technically possible?
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figures out the optimal frequency (it uses multiple separate ones for the same cell) and the optimal
transmission power (for both downlink and uplink transmissions).
Part of the definition of optimal here is not so strong as to interfere with neighbouring cells more than necessary
In theory, you could implement some inter-AP protocol as part of a WiFi standard to allow them to
determine their resepective
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The WiFi devices actually cooperate, it's part of the spec. A WiFi network consists of more than just the clients attached to it - it includes *all* clie
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Re:If only all wifi devices could work cooperative (Score:5, Informative)
Hi, I'm working for The Serval Project [servalproject.org], and like other projects related to wifi mesh routing, we do have high level goals like this. And we're actively trying to make them a reality.
One of our staff just returned from a presentation to IEEE, to propose a more open standard for the next 802.11 spec.
The basic premise of our proposal is that the protocol for using wifi devices to route traffic should be dealt with in kernel or user space. Not in the radio spec. And that adhoc, and 802.11s are useless for this task (Damn you BSSID, why you change?). We also think that security and perhaps even error correction should be dealt with via a VPN or baked into the application layer.
We want the next wireless spec to include a basic packet radio mode, operating in any unlicensed white-space spectrum, that gives as much control as possible to higher levels of the OS. So that new interesting ideas are easier to experiment with and implement.
And we've been invited to the next IEEE working group to help make it happen.
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Like IMing in the same house (Score:2)
"Honey, did you leave the microwave on?"
"I don't know, Dear, let me log into my PC and check."
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Right, because no one has neighbors in close proximity or anything silly like that.
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Erm.. Is it even possible to "leave the microwave on?" Aren't they all on timers?
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Nomally, yes.
~20 years ago I had a microwave with a dial timer that stopped working but still kept the mic "running". Sometimes it would blow an internal fuse if you opened the door while operating, I got tired of changing the internal bit and wired it out. The part bypassed was the door safety assembly. Basically the thing would run with the door open and never stopped.
I had to warn anyone that was over to hit RESET before opening the door. Girlfriend moved in and we kept her microwave. Wimp.
Serious en
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Microwaves have never been shown to have any link whatsoever with cancer, nor has there ever been demonstrated any means by which they might cause it. The radiation is non-ionizing, and the effects we've seen it cause can be summed up as thermal (heats up water molecules really well), and electric (can induce arcing on metal).
If you can think up some reason microwaves are more likely to cause cancer than infrared, visibile light, and radio waves, Im sure the listening scientific community would love to hea
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Microwaves enable you to prepare food, which may contain carcinogens. I doubt that you can do that with infrared, visible light or radio waves.
SCNR
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In fact there is an entire market based around doing with infrared as a replacement for microwaves because they do it better.
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Nomally, yes.
~20 years ago I had a microwave with a dial timer that stopped working but still kept the mic "running". Sometimes it would blow an internal fuse if you opened the door while operating, I got tired of changing the internal bit and wired it out. The part bypassed was the door safety assembly. Basically the thing would run with the door open and never stopped.
I had to warn anyone that was over to hit RESET before opening the door. Girlfriend moved in and we kept her microwave. Wimp.
Serious end note: I called my microwave "Ol' Auschwitz".
Why not just wire the fuse part outside the unit?
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Now I'm 45 and stupid.
Prolonged exposure to microwave radiation does that do you.
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Why is there still microwave oven interference? (Score:3)
I thought that shielding was well understood and in fact a good reason of the part why microwave ovens are a common household item.
Could anybody with experience in these matters explain where the leak is coming from, and why do they still exist? Is it impractical or physically impossible to have perfect shielding for some reason?
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My el-cheapo microwave says on the box that it has 1500 watts of cooking power. Wifi stuff works over a couple of watts.
I see those numbers and I'm not surprised that the one can bother the other, but I don't have the EM smarts to know how easy it would be to shield the microwave enough to get the emissions down to (the equivalent of) a watt or two.
Re:Why is there still microwave oven interference? (Score:5, Interesting)
WIFI is only allowed to transmit 100 mW (0.1 watt).
Even if only 0.01% of the microwave is leaking it is still more powerful than the WIFI. And even less is required if you do not have a perfect WIFI signal to begin with.
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Even if only 0.01% of the microwave is leaking it is still more powerful than the WIFI.
Usually it's not any leaking from the cooking chamber, those are pretty well shielded, but the power supplies, which aren't well shielded.
I've read that it has to do with the AC duty cycle, but I previously had a Panasonic that ran on a DC inverter (supposed to make the microwave cooking better, but didn't) and it had terrible WiFi interference.
'Microwave robustness' and 802.11g didn't do a darn bit of good (maybe
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According to Wikipedia, the safety regulations are "5 milliwatts per square centimeter, measured 5 cm from the surface" (although it cites this as "over the lifetime of the device" - I'm unsure if that means "the total amount over its life" or "the maximum released at any time during its life"). Given their 28x38x25cm measures for a "standard" microwave, that comes out to 5.4 watts. Output power on most Wifi devices is 100-200mW. So yeah, it's completely plausible that a microwave can leak enough radiation
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In order to get that amount of microwave energy you'd need something in excess of 2kw of electrical energy. If you are in North America 1.5kw makes rather more sense as power consumption. The term "cooking power" could turn out to be as much a fiction as "music power".
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It probably doesn't even say exactly that on the box.
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If a microwave oven were leaking enough energy to be harmful, wouldn't that energy be perceptible as warmth/pain? Let's suppose that's not the case; what type of injury could be inflicted that would not be apparent to the exposed person?
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Leaking enough to be harmful to what? You can certainly feel 5 watts of RF under the right conditions like sticking your finger into a helical resonator but not from a diffuse source like a leaking seam or inadequate feedthrough.
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Really? I installed my Whirlpool microwave and neither my cell nor my GF's cell (ATT & Verizon) receives any text, call, or email while in the microwave. I test it often.
[joke]
Well, I repeated your tests and I can confirm: not only my cell does not receive any text, call, or email while in the microwave, but even for infinite time afterwards. Maybe due to the apparent design change, which occurred during the microwave exposition? You did not mention any visible changes...
Used methodology: put cell into microwave, set at least 700 W power, apply for at least 1 minute. Visible changes comes after some first 10 secs. My neighbor even reported (using the same methodology) e
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so what, celphones work on a different frequency, shielding is not the same as a Faraday cage
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It doesnt work that way. Microwave ovens are designed to block microwave radiation at the wavelength they produce; sticking a completely different EM source inside it and noting that the radiation isnt blocked doesnt show you anything. Wavelength plays a big part in it.
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All that proves is that it dosn't block 1.9GHz, 1.8GHz, 850kHz, 900kHz, 450kHz or whatever the phone was using.
You might just as well put a battery powered radio inside. Or even declared it was not "properly shielded" because you could see inside!
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I don't have much experience with this kind of thing but from what I can extrapolate from this [wikihow.com] wikihow article it's just that some microwaves are poorly designed or are old.
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Perfect anything is impossible to achieve when dealing with microwave devices, in my opinion. Particularly shielding - you can reduce it down to a point, and it gets expensive the lower you go. For instance, "quiet chambers" used when testing for EMI compliance typically have doors with beryllium-copper fingers that try to create a faraday shield to keep out external interference. I've never seen any commercial microwave oven that uses these - for good reason too, since they're expensive and won't last very
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Aren't the fingers there to avoid reflection of the inside radiation? In that case, they would be counter productive for microwave ovens; you definitely do not want the internal radiation to be absorbed by the walls.
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Finger stock breaks up seams which otherwise would act as slot antennas. Sometimes mesh wire tubing is used.
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yes it is impossible to have perfect shielding, for your average 30$ microwave, and even if it would probably blow something open from steam pressure inside
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That ground prong on the end of 6 feet of inductive power cord is not going to do anything for RF shielding even at a frequency an order of magnitude lower. The ground is for safety.
I've done this plenty (Score:5, Funny)
Microwave channel = 2450 MHz (Score:2)
Most microwaves oven are supposed to work right at 2450 MHz, so if you want to avoid microwave ovens (which you should if there's one in the area and it's used often), you want to use the highest or the lowest numbered WiFi channel -- you don't need a spectrum analyzer to tell you that.
But if you want to see the results of one on many microwave ovens ... here you go [bldrdoc.gov]. It looks like the exact bandwidth used by their signals vary quite a bit, though my advice above still stands in the majority of cases.
Of cou
If you buy one of the CHEAP WiFi Detectors (Score:3)
(not to be confused with the WIFE Detector(tm) )
then you can indeed detect a microwave oven, and pretty much anything that spews out parasitic signals from 1500-3000 Mhz.
*Technical explanation coming up* ;)
This is due to the cheap construction of those So Called WiFi detectors, they're not digital, they're in fact analog receivers that only detect any modulation on the band (very VERY wide-band / BroadBand reception)... it's just a glorified Crystal Radio with a small half-coil, 3-4 transistors to amplify anything...any signal picked up by the small 1 cm internal antenna, and 1 transistor to switch on a led (or 3-4 resistors, if it's sophisticated and have 3-4 leds...ha ha)
There...now the Chinese can mass-produce them, I just literally gave you the schematics for it... ...oh wait!
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Could it be possible to create a 3D image of your surroundings by some triangulation and delicate signal processing of WIFI signals? The more there are microwave sources the better the result.
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That would be tricky. A lot of things tend to reflect the 2.4 GHz signals, and the reflections interfere with the signal. A fun experiment is to attach a 2.4 GHz antenna to a spectrum analyzer, and move it around. Just moving it a few inches back and forth has enormous effect on the signal strength (that's why a lot of gear has two antennas).
Maleficence (Score:2)
I was going to say how this sounds like a potential invasion of privacy, but then I realized that the police knowing you have a microwave or Xbox controller probably isn't something to worry about.
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You're correct; however, if I can detect someone's 2.4GHz wireless security camera(s), it's another story. It really would be an invasion of privacy at that point, assuming I'm intent upon invading your privacy.
Microwave covers the whole 2.4 Ghz wifi band (Score:1)
The only escape is the 5 Ghz band, but if you could use that, you'd be doing so in the first place.
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You're agreeing with my me. 5 Ghz doesn't penetrate stuff well at all, which means obstacles both help prevent outside interference as well as block your desired signal. When you can use it, it's great, but you often can't.
Source (Score:1)
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So where's the source code for this?
Not the sources, but they put out a couple of FREE iOS and Android Apps: http://itunes.apple.com/us/app/network-test-networktest-org/id433948720?mt=8 [apple.com] https://market.android.com/details?id=com.measurement.frontend [android.com]
So, no maemo/meego version then (Score:1)
Drat
Android phone please (Score:2)
Using NetStumber to measure microwave oven leaks (Score:1)
I had a microwave oven that consistently stopped my Netflix videos streaming over WiFi every time someone made a cup of tea.
I was able to prove a contributing issue was related to its poor door seal letting microwaves out using the free WiFi tool NetStumbler [wikipedia.org] (Also known as "Network Stumbler").
NetStumbler has can graph the Signal/Noise ratio of a WiFi station over time. If you put a laptop running NetStumber in a microwave (Don't turn on the microwave!) you should see the signal to noise ratio drop 30 dBm [wikipedia.org] a
But can it detect... (Score:2)
But can the researchers detect the government mind control rays transmitted from cell phone towers? If it could do that, I wouldn't have to wear this tin-foil hat all the time!
New function for tricorder-like apps. (Score:1)
Handy-dandy microwave signal detector! Hey, if your app can tell between wifi and microwave then that would be a neat thing to be able to track.
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Sadly the 1950s style jiffy pop always seems to burn the popcorn.
Toaster ovens burn the bag.
That leaves hot air poppers, but they spew rf noise worse than microwave ovens do. (The momentary contacters in the hot air blower act like spark gap transmitters, and blanket a large spectrum. Same with hair driers btw.)
So, how am I supposed to make popcorn, eh?
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Bag of regular popcorn.
Medium size pot, with lid
Oil, or I prefer bacon grease
Put it on the stove, on just above medium *
Put a thin layer of oil in the bottom
Put two and only two kernals in it.
When the first one pops, turn the heat down a little *
Put in one and only one layer of kernals on the bottom
Put the lid on the pot
When it is 2 seconds between pops, it is done.
During popping, you may give the pot one and only one shake.
* your stove settings may vary
UW! (Score:1)
Eh, what? (Score:3)
First of all, switching channels to avoid a microwave is futile... the magnetron isn't all that frequency stable and the peak tends to wander across the band as a result.
Second, 802.11g/n uses OFDM. You get narrowband interference, you reduce the rate on the affected subcarriers. It's built in.
Third, I'm fairly sure using a wifi card as a spectrum analyzer has been done before.
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It is futile for another reason as well. The direct conversion receivers used in consumer level 802.11 equipment have atrocious out of channel rejection and dynamic range so the magnetron output only needs to be in the same band to cause significant problems.
How about one that can't (Score:2)
True Story (Score:3)
In 1992 I was at an IEEE 802.11 meeting (that's WiFi, if you didn't know it by that name). My company was presenting a "pre-standard" wireless LAN design that we were developing, to be considered as a contribution to the standard.
Someone asked "Why does your design have so much error correction coding? Are you expecting the RF environment to be that bad?"
I replied, "Well, I haven't seen any 'Listen Before Cook' microwave ovens out there!"
This got a few chuckles and we moved along.
Many years later, I was doing some patent searches, and I came upon Patent number 6,346,692, titled "Adaptive Microwave Oven"
I'll be damned! Somebody actually patented the "Listen Before Cook microwave oven!"
So now we have WiFi devices detecting microwave ovens. That seems obvious to me. But I'm still waiting for a commercially available microwave oven that will avoid stomping on my WiFi signal :-)
FWIW, The 802.11 Media Access Control (MAC) protocol effectively avoids microwave ovens most of the time, because the magnetrons in consumer microwave ovens only operate on a "half wave" basis. This means they're off at least half the time. A microwave oven during its "on" time looks indistinguishable from another WiFi transmitter, and so your WiFi device simply waits until the microwave oven turns off before transmitting the next packet. This results in slower throughput, but isn't a show stopper.
The bigger problem is that since the microwave oven doesn't listen before turning on its magnetron, it tends to "stomp on" your WiFi signal occasionally. This, combined with the fact that the majority of IP based communications is TCP (and TCP sees every packet loss as congestion, causing it to slow down for the next few-to-tens of seconds), results in more throughput loss than is strictly related to the number of packets "stomped upon."
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But I'm still waiting for a commercially available microwave oven that will avoid stomping on my WiFi signal :-)
That'd be nice, but I'm waiting for a reverse microwave: instead of heating food by exciting water molecules with microwaves, it cools stuff by sucking out the microwaves... so you put your warm beer in there and a minute later its frosty cold and completely drained of microwaves.
Handy smartphone and ps3 controler detector (Score:1)
But apparently can't detect name interference... (Score:2)
They should have done a little Googling before they decided on a name...there's already a commercial product (albeit a very different one) that uses the name "AirShark":
http://www.itrbo.com/airshark/airshark.html [itrbo.com]
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So we proved what we already knew? (Score:1)
Let me get this straight. These researchers managed to prove, on what was likely a proprietary platform, what we already proved on an open platform? The Ubertooth has been proving and showing this interference for months now. [Hak5 - Youtube [youtube.com]]
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There's also the Ubiquiti AirView, which I see is available for as low a $40 now.
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