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Wireless Networking Communications Hardware

Escaping WiFi Interference In The Modern Dorm Room? 144

j.cherney writes "I recently moved my son up to a dorm at Michigan State University. We set up a wireless router (D-link) and everything worked well-until the rest of the dorm moved in. Now he is getting intermittent outages which I am quite sure is related to the large numbers of cordless phones on the 2.4ghz frequency. So my question to everyone is: Is there anything that I can do to make wireless work in this environment? Obviously I'm not willing to buy everyone in the dorm a new cordless phone! Is one brand more resistant to interference than another? Is there a filter than can be installed? Or is he S.O.L.?"
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Escaping WiFi Interference In The Modern Dorm Room?

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  • Suggestions... (Score:5, Informative)

    by CommanderData ( 782739 ) * <{kevinhi} {at} {yahoo.com}> on Sunday October 24, 2004 @06:30PM (#10616557)
    1) Switch to 802.11a (in the 5.4Ghz range, so the cordless phones will not bother it)

    OR

    2) Wallpaper the dorm room with tinfoil (has the added benefit of blocking government mind control rays)
    • by redhotchil ( 44670 ) on Sunday October 24, 2004 @06:31PM (#10616560) Homepage Journal
      For the college student, 2 is pretty much the only option available.
      • but if daddy pays...option 1 just *might work*
      • Re:Suggestions... (Score:4, Interesting)

        by Holi ( 250190 ) on Sunday October 24, 2004 @07:53PM (#10617034)
        I don't know I picked up a Proxim Harmony access point (802.11a) for $10 on Ebay, pretty much the most affordable access point I have ever found.
      • Re:Suggestions... (Score:3, Informative)

        by caseydk ( 203763 )

        At Microcenter last Friday (10/15), I picked up an 802.11a/b/g router with a 4-port switch built in and a 802.11g usb keyfob for $137... or $107 after rebates.

        If this cost is split with a roommate/suitemate or two, this is not bad at all.
      • "For the college student, 2 is pretty much the only option available."

        For the college rooms I've seen, it would probably cost less than $3 in tinfoil...
      • True, but it's a pain in the butt to install it all. Have one of your buddies convince your floormates to "prank" you, by covering your entire room in aluminum foil. Act really pissed, and then never take it down.
    • Re:Suggestions... (Score:3, Insightful)

      by nocomment ( 239368 )
      or get a different antenna. :-)
      The router/nic will listen to whatever is loudest. Go pick up a bigger antenna. 7dbi should do it.
      • Re:Suggestions... (Score:4, Insightful)

        by Gherald ( 682277 ) on Sunday October 24, 2004 @07:41PM (#10616980) Journal
        > or get a different antenna. :-)
        > The router/nic will listen to whatever is loudest. Go pick up a bigger antenna. 7dbi should do it.

        Yes, because if everyone got a bigger antenna that would go a long way towards solving wifi interference problems... genius man, pure genius.
      • Why, so his access point can hear more and avoid transmitting? :)

        Wifi is a carrier sense media, enhancing the ability for his AP to pick up even more noise is just going to aggrevate the situation.

      • or get a different antenna. :-)
        The router/nic will listen to whatever is loudest. Go pick up a bigger antenna. 7dbi should do it.


        Just make sure it's a DLink antenna. DLink will most likely be the only manufacturer who has a certified antenna for their gear. If you're going to start a pissing match, you really don't want to be the one breaking the law. Believe it or not, it's legal for Superpass to sell an antenna that isn't legal for you to install.

        He could put a sector antenna on the AP (like the ATN2
        • Yes, though, I was under the impression that the recent court rulings had pretty much said fucking arund with your own antennas is OK, within certain limits.

          But, I might very well be wrong. Maybe somepone not as sleepy as I am right now feels like digging around old /. articles...
    • by hackwrench ( 573697 ) <hackwrench@hotmail.com> on Sunday October 24, 2004 @06:59PM (#10616732) Homepage Journal
      Build and turn on a jammer. Everyone else will go buy phones on a different frequency. Then the frequency will be free for you to use your network with.
      • My exact thought... except I think it might be illegal. Also, don't leave the jammer on all the time, at least not in your room. Maybe find a janitor's closet where it could lay undisturbed, without any evidence pointing to it's owner...
        • The spectrum is unliscenced. Every device just has to deal with it. Some may be better than others for the job ;)
          • Yes, but pissing off your dorm mates (and professors, and "the college" as a whole) is not a good idea.
            • Re:Suggestions... (Score:3, Insightful)

              by jd ( 1658 )
              Only if they can track the problem to you. I'm sure if you look hard enough, you'll find somewhere that's large enough to take a jammer, sufficiently out of sight for it to not be obvious, and sufficiently far from your room to not be traceable back to you.

              Ideally, the jammer should output more of a noise than a continuous signal. It'll look more natural and/or unintentional.

              However, if you want something spectacular, you want to use the standard 110v power line for your input voltage, and you want to u

    • 1) Switch to 802.11a (in the 5.4Ghz range, so the cordless phones will not bother it)

      I can confirm that this works. Back in 2002 I worked for the Tulane Computing Store as a student job and we recommended this to students and teachers who had the interference problems. It seemed to work since I don't remember anyone coming back to get their money back.
    • OR

      3) spread rumors that you and anyone else with the right equipment can listen to cordless phone conversations in the building. A few additional rumors about 'things you heard while sniffing phone conversations' will also help a bit. Students are a gullible lot.

    • I use an 802.11a network at home to avoid interference from a 2.8GHz phone also. It works fine but the range is lousy -- doesn't penetrate more than one layer of wall/floor so bedroom computing doesn't work very well.

      802.11a also has the advantage of not being widely used in the non-business environment so they may be overlooked by casual wireless sniffers or cheap neighbors loking to ride on your wireless LAN.

  • Google turned up http://w3.antd.nist.gov/pubs/golmie.pdf. Even though it's about Bluetooth and 802.11b, it might help. Also: http://hardware.mcse.ms/message90850.html for information on bandpass filters. Hope this helps!
  • by ForestGrump ( 644805 ) on Sunday October 24, 2004 @06:34PM (#10616576) Homepage Journal
    I'm a 3rd year junior, I've since moved off campus but this is my suggestions.

    1. The, IMHO,most logical suggestion. A dorm room isn't that big, buy a 50 foot cable. If you insist on keeping a wireless network around, try going for 11a equip. Kinda hard to find but a week or 2 ago, worst buy...er i mean bestbuy had a sale for a dual band 11a/b/g router.

    2. See if there is a campus wireless, and if it covers the dorm areas. If yes, convince EVERYONE to kill their AP and use the campus wireless. As for the phones, not much you can do if you're not buying everyone a new phone.

    3. You could try a game of "my transmitter is more powerful than yours" and use ext antennas to put out a stronger signal...but not that practical.

    Grump
  • by gl4ss ( 559668 ) on Sunday October 24, 2004 @06:38PM (#10616595) Homepage Journal
    like.. could having too many of them in the area cause that?

    of course obvious solutions: bigger/better antenna.
  • Faraday Cage? (Score:3, Informative)

    by Froze ( 398171 ) on Sunday October 24, 2004 @06:50PM (#10616667)
    If you have a microwave you know exactly how to build one. The freq. that a microwave functions at is damn near spot on 2.4 GHz so all you need is several rolls of metal window screen where the mesh size is the same as your microwave.

    Oh Yah, you also need to make sure that it is well grounded, you can tie directly to the ground lug of any triple prong outlet, or steam pipe, etc.

    Free Flat screen whatevers [freeflatscreens.com]
    • If you have a microwave you know exactly how to build one. The freq. that a microwave functions at is damn near spot on 2.4 GHz so all you need is several rolls of metal window screen where the mesh size is the same as your microwave.Oh Yah, you also need to make sure that it is well grounded, you can tie directly to the ground lug of any triple prong outlet, or steam pipe, etc.

      This also has the advantage of identifying appliances that have ungrounded "hot" metal cases by electrocuting anyone touching the
      • FYI, the ground leg of a properly wired outlet is physically attached to an earth ground at the nearest panel. Thus any "hot case" would also be a shock risk for a switch plate screw/outlet cover screw/water pipe/steam pipe/puddle of water/or other circuit direct to ground.

        BTW, you will never find a UL listed hot case in America unless it has been modified by the owner in an amazingly ignorant fashion. You would have to not only short the hot leg to the case, but you would also have to disconect the the ap
        • Re:Faraday Cage? (Score:3, Interesting)

          by bluGill ( 862 )

          Mostly correct, but the toaster is a special case. The toaster is ungrounded because it is safer when (not if) someone puts a knife in it. For just about everything else, grounds are required by UL. Toasters are about the only thing where having a ground would make it fail UL!

    • I've been doing some wireless surveys on my campus and one of the cisco geeks pointed out that the best sheilding he had seen for b/g wireless was chain link fence. It's something about the size of the grid being perfect to block that frequency range.

      So what you do is have your son go out some night a construction site and aquire 7 or 8 of the sections of the temporary fencing.
  • by Myself ( 57572 ) on Sunday October 24, 2004 @06:53PM (#10616688) Journal
    First: I'd guess that some of the interference is coming from other 802.11b/g gear, not necessarily cordless phones. It all defaults to channel 6 from the factory, so try 1 or 11. Or load the ETSI firmware and use 14, and just don't tell the FCC.

    Second: Try some FHSS gear, it seems tougher in noisy environments than DSSS. The old Proxim RangeLan equipment is cheap.

    Third: Get out of 2.4GHz entirely. Go go 5GHz with 802.11a, or 900MHz with older Aironet gear.

    Fourth: It's a dorm room, and worse than that, it's an MSU dorm room. What is it, 4x8 feet? Stick with wired. Get a real patch cord that uses stranded conductors, as the solid stuff is too stiff and will stress the connectors.
  • A dose of reality (Score:2, Interesting)

    by jbarr ( 2233 )
    Obviously, this situation sucks, but it does give the son a dose of reality. Move into a new neighborhood? Contend with interference. Move into a new apartment? Contend with interference. Sounds like a great opportunity to test out his technical and negotiation skills that he'll need once he enters the post-college real world.
  • Hang sheets of lead on the walls. Should block out most things.
  • hmm (Score:3, Informative)

    by man_ls ( 248470 ) on Sunday October 24, 2004 @07:15PM (#10616835)
    Nothing you can really do in this case.

    However,

    my Belkin equipment has a special mode it says you should enable in high-interference environments. My guess is, it either adds additional error correction, or boosts the output, or something, at the expense of a little bit of speed.
  • by OldMiner ( 589872 ) on Sunday October 24, 2004 @07:52PM (#10617024) Journal

    You probably already read the AUP for MSUnet [msu.edu]. It specifically addresses the issue of NAT devices, a common concern at universities. The issue is that normally a person must register their MAC on the network to gain access. Then any nefarious activity that occurs on the network can be tracked to the individual user who registered that MAC address. For now, let's ignore the possibility of being able to change the MAC address on some ethernet cards.

    By introducing a NAT'd device, you open an entry point to the network to anyone, even those not with proper access, and you rely on the good will of these nameless souls not to do bad things in your name. So if anyone ever becomes evil while connected to your basepoint, it becomes your responsibility to deny access to your AP or remove it from the network.

    • You're assuming they're running an open access point.
    • by toddestan ( 632714 ) on Sunday October 24, 2004 @09:06PM (#10617491)
      Most schools, including mine, ban wireless routers for this reason. They want to track who does what with what computer on the school network. They also ban regular wired routers too, for the same reasons. You might want to check to see if Michigan even allows wireless routers - they probably don't. While a wired router is hard for them to find, my school will sniff out student-run wireless and bust people for running them. So the first thing I would do is just make sure you aren't wasting your time trying to get this to work.

      Even if they do allow wireless routers, you might want to re-evaluate just how badly he needs that wireless. Dorm rooms aren't that big - just buy a long cable. Or buy a cheap hub and run a cable to the desk, to the bed, and anywhere else he's going to use a laptop. One of my roommates did just that, worked fine. Lastly, you might just try unplugging your router and seeing if you can pick the school's wireless if they have it. If he's really lucky, he might get a good signal from some other sucker's wireless router. In which he can download as much music, movies, warez, and p0rn as he wants, and if the RIAA/MPAA/BSA comes around, or if the ResNet people get annoyed at the excessive bandwidth use - they'll bust the poor guy who registered the MAC address on that router.
    • Ah... But if you use a wireless access point, which is just a bridge, you won't have NAT and you can use your wireless NIC as long as it's registered.
    • For now, let's ignore the possibility of being able to change the MAC address on some ethernet cards.

      Not some. All. Macshift for Windows XP can do it, and it works for damn near every network card. Wireless too. http://macshift.natetrue.com [natetrue.com]

  • Alternative (Score:4, Insightful)

    by drix ( 4602 ) on Sunday October 24, 2004 @07:58PM (#10617062) Homepage
    It could be due to huge numbers of people "stealing" his wireless. No, really--those cheapie consumer broadband routers don't fare well with more than a handful of simultaneous users. I'll bet a lot of people are turning on their laptops and finding that wonderful little connected icon in the bottom right and not thinking twice. Even with in-room connections, sometimes it's hard to get your ass off that bed :)
  • by gorim ( 700913 ) on Sunday October 24, 2004 @07:59PM (#10617084)
    FCC Part 15 rules state that this device must accept any interference, including interference that might disrupt its operation.

    This means that any other wireless routers, cellphones, microwave ovens, etc... are free to wreak havoc on it, and vice versa.

    Having said that, you can always spend more money to upgrade to the newest 802.11 wireless protocols that operate in a different range. It will still be another 6 months before prices drop enough for students without rich parents can afford them.

    Honestly, as a young man, I am sure he can tough it out with a CAT5 cable like we did in my day and age, before these new fangled wireless things made life easy. It won't be chic, and it is certainly very old-fashioned, but it gets the job done. Its quite possible your son might never have seen a CAT5 cable before, so now its time for you to show him how Daddy use to do it.

    Or you can have Grandpa come down and show him how they did it with 10base2.

    • Bah! Back in my day we used ARCNET [arcnet.com], Twinax [bosweb.com], PLIP [tldp.org], or if we were really lucky, SLIP [ohio-state.edu], and WE LIKED IT!!!
    • by bitingduck ( 810730 ) on Sunday October 24, 2004 @09:08PM (#10617501) Homepage
      We huddled around a 110 baud acousticoupler, and if you read something that was funny the laughing would generate errors in the connection.
    • FCC Part 15 rules state that this device must accept any interference, including interference that might disrupt its operation.

      That is true -- the FCC won't come in and save you. But there are still ways to work around it ...

      The 2.4 gHz band is probably toast. WiFi uses spread spectrum, as do some better cordless phones, but the cheap cordless phones just use one chunk of bandwidth and don't care what else is there too. And then any microwave ovens anywhere nearby will scramble all the 2.4 gHz st

  • Start using WiFi properly and encourage others to do the same. WiFi should only be used when a wired solution will not work. If the distance is only 10ft and wireless can penetrate it, most likely a wired solution will work.
    • Who wants to string a wire across the dorm room to the computer in your lap so you can access the network while laying on your bed?

      Then go through the hassle of unplugging it and storing it every time you turn your cpu off and on.

      It may not seem like that much of an inconvenience, but why put up with it when there's another solution that's possibley, in the long run, less of a hassle.
      • by shaitand ( 626655 )
        Like I'm concerned with what is a hassle for you. Sorry but wanting to browse porn in the comfort of your bed isn't a good enough reason for clogging my airwaves.
    • Not everyone who reads the AskSlashdot are in the *exact* same situation. I am having a very similar problem in my apartment (which is a lot bigger than a dorm room). I'm reading this so I can get suggestions to my problem. Not everyone looking for answers to this question is in a 10x10 room. I'm sure there are many others like me who are getting WiFi interference in apartments and even houses, who would like answers other than the smart-ass "use CAT 5".
  • by perlbaile ( 752196 ) on Sunday October 24, 2004 @09:09PM (#10617505)
    I work in a noc doing cpe (customer provided equipment) support for small companies in pop in downtown Toronto. Since we've introduced cpe enabled wifi, I've turned on snmp polling for stats on connectivity, signal strength etc, and its open my eyes as to where things can go wrong with wifi in a chaotic enviroment. We have about 64 + access points in a building that is less that 300 feet long, and 80 feet wide, that is two stories, and we have no radio interference. 99% of the cases of lost ip transit to wireless endpoints like laptops, bridges or a/ps were due to either Trojans/spyware/malware/viruses swamping the cpe's wan interface, nat process or someone cracking wep and swamping the connection with Kazaa traffic. Either way, I suggest you stick a network sniffer like snort on the wan ethernet interface of the dlink inline (an old p200 w/ 128 megs of ram and an 8gig disk makes a great sniffer, running linux, freebsd or openbsd), and watch what traffic patterns you see. Your son will be able to see what traffic is being used, and will have the tools he needs to take responsiblity for his own connection. Isn't that what great geek dads are supposed to do for their kids ? It might save you a few rolls of tinfoil.
  • by sakusha ( 441986 ) on Sunday October 24, 2004 @09:14PM (#10617533)
    This device [amazon.com] is the simplest solution to your problem.

    No, I'm not kidding.
  • All the people in my wing make fun of me and think I'm weird for doing this, but I'll share it with you and maybe you'll be one of the ones who understand.

    I've mastered a new technique employing "direct transcranial wireless transmission." All you need is about a 12' lenghth of aluminum foil, two coat hangers, and a pair of 9v batteries. I just added an extra battery yesterday to boost the signal and now I'm getting 1.1 Mb signals--wait...they're transmitting--from Andromeda, and also Tau Ceti. They...

    • Hello. I'm Galactic Sheriff Balcolm of the Andromedan Federation, and you're violating the Andromedan DMCA by intercepting and decoding our transmissions. Please remove your foil and step away from your saucer.
  • by Anonymous Coward on Sunday October 24, 2004 @09:54PM (#10617749)
    My god, you live in a *dorm* and you need wireless networking?

    You're the wifi version of the idiots I lived next to in college with GIGANTIC STEREOS jammed into little 8ftx8ft rooms. Did you know ALL music sounds the same when filtered through the low-pass filter known as "the walls"? I didn't!

    Yeah, when you're in college, you're king of your world and entitled to everything. Whatever.

    Besides, with the wireless, you're just letting that freaky Linux guy next door who wears a cloak see what kind of porn you like to hit it with.

    You don't need a cordless phone either, by the way. You live in a damn CLOSET!

    (Oops, this was the guy's dad. Adjust pronouns appropriately.)
    • As someone who lives in a dorm at Rutgers University...

      Ok, The huge stereos? Ok. You've got a point there. I don't need to share my music preference with people down the hall. I *do* have a THX rated surround sound system on my computer though. Why? Games. Movies. I want them to sound good. I live in a box. When I watch a movie, I don't want to feel like I'm watching a movie... in a BOX.

      The wireless? My dorm is broken up into 10 smaller "houses" attatched by tunnels and such, and each house has it's own l
      • Right, putting six inch concrete walls in the inside of the building is so feasible. Pumped concrete is Expensive, there's a reason they don't use it for interior walls, not the least of which is that interior walls six inches thick will consume a lot more space than the ~4" walls they usually put in.

        If they put six inch concrete walls in, your cordless phone wouldn't work either, and neither would cellular phones, which are the real solution. I ditched my land line and I've never looked back. Most studen

        • the walls here are 4-6" concrete. About six inches between rooms, and four inches betwen my room and the hallway. My campus was designed by an archetect that usually designed jails. We call our campus "The Rock" as a little joke. And land lines here in the dorms are included for free, you just need to pay if you want long distance. And shit does work, you just have a little bit of a range issue, but I have a massive window that faces the interior of the quad, so one antenna of my access point sends the sign
          • I'm a college student. I'm glad your Uni has jobs that pay properly, but I'm in a community college and they don't pay diddly here because California's community colleges (like every other primarily governmentally-funded school) are seriously low on cash. There are quite a number of important positions here which have been board-approved but for which there is no funding.

            Most college kids are spoiled. I'm glad you're pulling yourself up by your own bootstraps but the majority of you (by you I mean the y

            • because majority of people here at Rutgers ARENT spoiled by mommy and daddy. Sure there are the rich lil sorority girls and the guys that drive mercedes and jaguars and crap, but majority aren't. And I take offense to assuming I'm some spoiled little college brat. I'm defensive over it after all the work I've put into it.
        • the walls here are 4-6" concrete. About six inches between rooms, and four inches betwen my room and the hallway. My campus was designed by an archetect that usually designed jails. We call our campus "The Rock" as a little joke. And land lines here in the dorms are included for free, you just need to pay if you want long distance. And shit does work, you just have a little bit of a range issue, but I have a massive window that faces the interior of the quad, so one antenna of my access point sends the sign
    • so true, so true...

      As for a solution, try airpwn, it worked wonders for me, everyone stops using wifi after they feel the power of goatse.cx!
  • by abdulla ( 523920 ) on Monday October 25, 2004 @02:15AM (#10618691)
    Have you ever thought he might be faking it so he doesn't have to talk to you? Want hime to look after grandma this weekend and suddenly his line drops? Clip the cheeky bugger over the ears, I say.
  • fixes (Score:3, Informative)

    by beegle ( 9689 ) * on Monday October 25, 2004 @06:49AM (#10619512) Homepage
    1) Fire up NetStumbler (or your OS's equivalent) and see which channels are in use. Remeber that 802.11b/g "bleeds" both up and down at least one channel. Pick the "least-busy" channel. Failing that, pick the one with the weakest (i.e. "easiest to clobber") signal.

    2) Depending on your school's policies, see if you can turn on bridging or otherwise share the connection (some schools are okay with it so long as you bridge and don't use NAT). If your connection works, others might use it and shut off their own connections. This probably involves talking to neighbors with their own APs.

    3) Talk to a neighbor with an open AP and see if you can use that one rather than your own. Most people are cool about that sort of thing.

    4) If you can't share, think about -reducing- the power of your AP, and see if your neighbors are willing to do the same. This is the airspace equivalent to "quiet hours". :-)

    5) Almost every new AP supports some sort of "interference robustness" or "microwave-safe mode" or something like that. All it does is reduce your MTU so that -some- of the packets make it through. Either turn this on, or manually reduce your MTU.

    6) Think about Bluetooth, 802.11a, or other "alternative" wireless technology. Bluetooth shares the same frequencies, but is often able to get an across-the-room connection even when the wi-fi space is totally screwed up.
    • Re:fixes (Score:2, Informative)

      by swarm scool ( 443902 )


      You did consider dropping the whole WiFi idea and using a cable right?

      Honestly there isn't anything wrong with cabled networks.
  • by stinkydog ( 191778 ) <<sd> <at> <strangedog.net>> on Monday October 25, 2004 @09:25AM (#10620408) Homepage
    Remove the magnetron from and old school 1500 wattmicrowave. Mount it in focal point of an old Primestar (or other satellite dish). Install a pistol grip and a trigger and you are good to go. Get a nice long extension cord and sweep the entire dorm with cleansing 2.4ghz waves. As long as you shield you AP before you begin you should be the only one left on the 2.4ghz frequency. Save your rig, it makes a nifty hot dog cooker. One warning, line you shorts with lead before you start so as not to cook your own frank and beans.

    SD

    PS Don't try this anywhere, ever.
    • How not [bellsouth.net] to test a magnetron...
      • How not to test a magnetron...

        I agree. The thermal switch isn't connected and there is no fan on that magnitron. You wouldn't want to melt down a perfectly good magnitron!
    • PS Don't try this anywhere, ever.

      I've really been tempted to try it after I got tagged with a photo radar ticket...

      A van with a photo flash hanging out the back would make a great target.

      The other tempting target is the kid on that leafblower powered scooter that makes so much noise. I wonder if I can kill it's CDI ignition.

      Where to plug in the magnitron along the highway is the problem.
  • by Ecks ( 52930 )
    Try a patch, corner, or parabolic reflector located at the access point. It should do the job and if it doesn't you will not have wasted much time or money. Freeantennas [freeantennas.com] has plans. You can use ordinary tin foil or screening to You want to orient the antenna to either block the interference or to project it's stronger coverage over your desired area. If that doesn't use a cat5 cable. -- ecks
  • You can investigate actual Wi-Fi surveys from wardrivers at wifimaps.com [wifimaps.com]. You can view your location, and see the other access-points in the area -- complete with channel data.
  • How big is your dorm room? 12x10? get some cat5 cable, sheesh. Wireless isn't always the answer.
  • Just get him a 50 foot long patch cable he can use to connect his computer to an RJ45 jack on his wireless router. Voila--no interference *plus* a faster connection. Most dorm rooms are tiny; a cable 25 feet long would probably work fine in most.

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