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Communications Network Networking

Grandma's Phone, DSL, and the Copper They Share (hackaday.com) 177

szczys writes: DSL is high-speed Internet that uses the same twisted pair of copper wire that still works with your Grandmother's wall-mounted telephone. How is that possible? The short answer is that the telephone company is cheating. But the long answer delves into the work of Claude Shannon, who figured out how much data could be reliably transferred using a given medium. His work, combined with that of Harry Nyquist and Ralph Hartley (pioneers of channel capacity and the role noise plays in these systems), brings the Internet Age to many homes on an infrastructure that has been in use for more than a hundred years.
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Grandma's Phone, DSL, and the Copper They Share

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  • What year is this? (Score:4, Insightful)

    by pak9rabid ( 1011935 ) on Friday February 05, 2016 @11:54AM (#51446393)
    Did I accidentally wake up in 1999?
    • by JoeMerchant ( 803320 ) on Friday February 05, 2016 @11:58AM (#51446431)

      According to my prof in 1987, doing a paper on Shannon's work puts you back in 1959. (Fuzzy logic was his thing, in 1987.)

      • I think the 1999 thing was more to having a discussion about DSL as if that is still a viable thing.
        • The scary thing is I believe a lot of people likely still use it because that's all they can get.

          Viable still applies if it's being sold, and lot of people are on it.

          According to this [digitaltrends.com] (which is from 2013), 18% of American internet usage was on DSL.

          I don't think "viable" means what you think it means. Used by tons of people and still actively sold ... well, it's outdated, but it's still viable.

          • by c ( 8461 ) <beauregardcp@gmail.com> on Friday February 05, 2016 @12:21PM (#51446641)

            The scary thing is I believe a lot of people likely still use it because that's all they can get.

            I'd be thrilled if I could get DSL.

            • First ... you poor bastard.

              Second ... exactly my point.

              • by c ( 8461 )

                Well, fixed wireless broadband isn't *horrible* compared to some alternatives. I went from DSL to 28.8k dial-up for a few years and that was... well, I didn't worry about congestion from neighbours, that's for sure.

                The only advantage of fixed wireless over DSL or cable is that I don't have to worry much about where I put holes in the ground; the only line coming onto my property that I care about is overhead.

              • And even if you get DSL you may not get the best DSL either. Older neighborhoods may be really bad in this regard.

            • You certainly could get something much better than DSL if your carrier could be bothered. That is your only choice because they have a monopoly or duopoly (which isn't really any better than a monopoly).

              I say this assuming you are in what is typically called the last mile rather than the actual last mile so far from civilization where there are no phone lines and sat communications are your only option. If you are in the arctic or at sea DSL capabilities may indeed be reasonable. To a point anyway, there is
              • by c ( 8461 )

                You certainly could get something much better than DSL if your carrier could be bothered. That is your only choice because they have a monopoly or duopoly (which isn't really any better than a monopoly).

                I have a choice of broadband wireless providers (two that I know of), or satellite broadband. Or I could use cellular service for the week or so before I maxed it out.

                I suspect in a few years I might be able to get fiber, depending on what they're doing with those lines they ran down the highway at the edge

              • Verizon can't even be bothered to maintain their copper lines for POTS, let alone offer DSL.
            • by Dragonslicer ( 991472 ) on Friday February 05, 2016 @02:04PM (#51447757)

              I'd be thrilled if I could get DSL.

              Your Internet connection is so bad, you only have enough bandwidth for one letter in your username.

              • by c ( 8461 )

                Your Internet connection is so bad, you only have enough bandwidth for one letter in your username.

                I s

                -*- click -*-

              • Though his child, c++, has better connectivity.

            • by muridae ( 966931 )

              I'd be thrilled if the DSL here was rated above 1 Mbps.

              Instead I get 10 Mbps cable with a low GB-per-month cap, that have actively hijacked google's DNS record to point to their own . . . I dunno, local cache or something. HTTPS Everywhere kept me from noticing for the last month.

          • "Viable still applies if it's being sold, and lot of people are on it.

            According to this [digitaltrends.com] (which is from 2013), 18% of American internet usage was on DSL."

            That's only true if those people have a legitimate choice and weren't duped into picking an obsolete slow connection by a monopoly refusing to modernize.

            The article mentions 6mbps, that isn't fast enough to support many modern and common household internet usages which means customers are being sold a system which is not viable. You migh
            • The article mentions 6mbps, that isn't fast enough to support many modern and common household internet usages

              Like what? It's enough for TV-quality streaming video, web browsing, VoIP, email and all the usual stuff I can think of.

              • The article mentions 6mbps, that isn't fast enough to support many modern and common household internet usages

                Like what? It's enough for TV-quality streaming video,

                No, this must be one of the few times where they actually mean 6 MILLI-bits per second (mbps) and not 6 MEGA-bits per second (Mbps). Six mbps means you get one character every, umm, 27 minutes. Six Mbps would be fast enough for streaming all kinds of things.

          • by Kjella ( 173770 ) on Friday February 05, 2016 @01:06PM (#51447163) Homepage

            It all depends on how far you are from the nearest central, 3-5 km out on basic ADSL is pretty crap. If you live close to the exchange or they've pulled fiber "close" and you get ADSL2 or VDSL you can get decent 10-50 Mbit. No doubt the growth is fiber though, here in Norway it's now 28% (+6%) fiber, 22% (-5%) DSL since last year.

        • It just reminds me of something that would have been in Wired, cira 1998-99.
        • It is. Plenty of things don't need more than the 5-10 Mbps you can typically get with ADSL, and if that's not enough there's VDSL2 which gets you tens of MBps.

          Besides, cable and especially FTTH are much less widely available.

      • by jon3k ( 691256 )
        I just finished Idea Factory [amazon.com] which spends quite a bit of time on Claude Shannon, a really remarkable guy. Great book, lots of interesting Bell history. My only complaint is that Unix is only mentioned twice in the entire book and the second time it's referred to as a programming language. I was really hoping for more Unix history, but it tends to focus on earlier Bell and the transistor, satellite, the anti-trust suit, etc.
    • Re: (Score:2, Funny)

      by Anonymous Coward

      What the hackaday people need is an ISDN line.

    • by msauve ( 701917 )
      "DSL is high-speed Internet"

      No, it isn't.
    • by dfm3 ( 830843 )
      Maybe old news, but seeing that DSL is still one of the only viable options for decent internet access in many parts of the US (excluding satellite), not completely irrelevant. Plus it's an interesting read from a historical and technical standpoint.

      If this is the direction that Slashdot's new ownership is taking the site, it's still better than the barrage of constant articles meant to bring out the sjw/anti-sjw trolls, or articles about Trump's verbal flatulence, or *shudders* anything by Bennett.
  • It's an hack (Score:3, Interesting)

    by Anonymous Coward on Friday February 05, 2016 @12:03PM (#51446477)

    Would have been nice if DSL never existed, dial-up would be the norm and websites would not be bloated, no social media or other bullshit.
    Instead companies keep profiting while not investing anything into upgrading the rotting copper.

    • by sims 2 ( 994794 )

      Yeah! They should have never started selling 1TBps fiber connections. We wouldn't have all these holovideos, remote windows and HD video ads that can't be muted. Most people don't even have their own computers anymore they just buy these mini-terminals and pay $10/mo applecorp for time on the applecore mainframe system.

      Yep If no one had ever bothered to build the infrastructure lots of things like youtube, netflix, remote surgeons, drones, video calling and working from home wouldn't be possible today.

      But y

    • The thought of a world of dial-up is terrifying but I share your pain regarding bloated sites.
    • by antdude ( 79039 )

      You can still use dial-up these days if you still have copper lines. :P

  • I mean this history lesson is fascinating, but really, I think most of /. knows how DSL works alongside voice on POTS.

    • by sims 2 ( 994794 )

      Yep we do.
      My problem is At&t.
      They want to run VoIP over my DSL line over my POTS line.
      Sounds reliable don't it?

      • You mean, they want to run VoIP over IP? How rude.
        At&t should allow for a dedicated low bandwith link with end-to-end connection, so you can run your VoIP without bad quality, jitter and lost packets.

        • by sims 2 ( 994794 )

          Yeah as of now I have POTS with phone > DSL modem > router.
          They are trying to get me to switch to POTS no phone > DSL modem with voip bridged back to pots line > router

          As of now I can lose phone without losing DSL and I can lose DSL without losing my phone.

          So then If my dsl goes down I lose both internet and phone.

          They've been advertising it as fiber optic phone service.

  • Sigh. (Score:4, Insightful)

    by ledow ( 319597 ) on Friday February 05, 2016 @12:12PM (#51446547) Homepage

    Looks like the new owners of Slashdot are also failing to combat the biggest problem faced by the site for the last few years.

    Junk making the front page that talks to me like I don't already work in IT or understand how common household technologies work.

    • You do understand that Slashdot has users from a wide variety of backgrounds? If you don't like it, scroll on by.

    • by Jeremi ( 14640 )

      Junk making the front page that talks to me like I don't already work in IT or understand how common household technologies work.

      Who are you? I didn't understand how DSL worked until I read the article, now I do. (Well, probably not, but now I know more than I did)

    • by amlu ( 3528237 )
      i disagree with you. for me its a technically minded article about technology that refuses to die and is still widely used. prefer reading that, much better than the recent stuff about another 3d printed gadget or some crazy gun related politics on another continent.
    • Disagree (Score:4, Insightful)

      by kbahey ( 102895 ) on Friday February 05, 2016 @04:31PM (#51449147) Homepage

      I disagree.

      Not everyone here studied this stuff. Some of us are self taught, or are experienced in other fields (software, systems admin) ...etc.

      So, having stuff like this is enriching to some here, and relevant to the site ...

    • Sure it's not "news" to many of us, but might still be interesting to some.
  • Cable is still copper and some areas have old plants that some of the big guys like Comcast are not really upgrading that much.

  • Claude Shannon (Score:5, Informative)

    by JustAnotherOldGuy ( 4145623 ) on Friday February 05, 2016 @12:23PM (#51446655)

    Claude Shannon was truly one of the unrecognized geniuses of his time.

    He was an amazingly brilliant man who got very little of the recognition he deserved. Virtually ALL modern-day communication depends directly on the algorithms and information theory practices he invented. He's quite rightly known as the "founding father of electronic communications age".

    He was still alive when I was in tech school, quite literally a "living legend".

    • by slew ( 2918 )

      Claude Shannon was truly one of the unrecognized geniuses of his time.... He was still alive when I was in tech school, quite literally a "living legend".

      Not sure how old you are, but he was apparently one of the *recognized* geniuses of his time. He has a long list of awards dating back to an AIAE 1940, a National Medal of Science in 1966, to the Kyoto prize in 1985 and quite a few lifetime achievement awards since that time...

      You don't get that type of swag and get to claim to be unrecognized (not that Mr Shannon was the type to crave any recognition, by some accounts he didn't really care for the stuff)...

      On the other hand, Rosalind Franklin, Emmy Noethe

  • Let's not forget that there was also the option of running high speed internet over the power lines. It does mess with Ham operators signals, though, so is not widely adopted. But in areas where it is adopted, people seem pretty satisfied.

  • Forget twisted pair. I have hundreds of cable channels and a 25 Mbps internet all brought into my home with a single coaxial wire.

  • by sbaker ( 47485 ) on Friday February 05, 2016 @12:47PM (#51446927) Homepage

    Many *MANY* years ago I was working as a software engineer at Philips Research in the early 1980's when they were looking into ISDN systems somewhat like DSL for the UK market - the business of sending anything over twisted pair copper is a nightmare. I wasn't directly working on the electronics (I was doing software) - but I shared an office with people who did...and they had a heck of a time characterizing the wires that their signals had to go down.

    As I recall, the problems mostly come where one wire is spliced into another. Much of this infrastructure was put in the 1900's and it's horrible. Sometimes wires are just twisted together and capped, sometimes twisted and taped, sometimes twisted and just left open to the elements, sometimes they are soldered. Sometimes the places where the wires are joined gets wet when it rains. Sometimes the tightness of the twisted wire connection depends on the ambient temperature. The amount of cross-talk between wires is all over the map as different kinds of insulation was used (and much of it has degraded over the years). At the subscriber end, there were all kinds of phones being used - plus ugly stuff like "Party lines" (where two houses share a phone line!) that had been abandoned leaving extra wires in the ground that were still connected to the network.

    All of those things affect the ability to get a decent amount of bandwidth down a wire that was never designed to do it. So the electronics has to be smart about the signal being reflected at each splice down the line and causing 'echoes', and designing affordable circuitry to detect and cancel those echoes was a nightmare. The amount of attenuation you'll get is all over the map - everything has to self- adjust and monitor to give it any chance of working.

    So, as poor as DSL can be - it's a miracle it works at all over crappy old telephone wires.

        -- Steve

  • These days in my country at least the router/modem provided by the ISP has a connector to plug an old (or new) land phone in, but it goes over VoIP. You have an RJ11 to phone plug adapter if needed.
    "Real" POTS is something you would have to look for, likely from the former monopoly ("historical") operator. Or maybe in a few areas left where things still have to go through the historical operator even when your ISP is something else.

    BTW grandma has had a DECT cordless for a while. Also, a permanently seated

    • Out of interest which country? Here in the UK phone service is still usually delievered over "real POTS". ADSL and VDSL (FTTC) users use filters/splitters to seperate voice and DSL. The cable company runs phone wiring alongside the cable TV wiring (and have done so since long before the days of cable modems).

      FTTH services may be an exception but those are still pretty rare here.

      • France. I should have been clearer maybe, it's POTS lines and the filters/splitters, but I believe the ISP may not bother providing the plain voice service.

  • F#$^#$^@ (Score:4, Funny)

    by barakn ( 641218 ) on Friday February 05, 2016 @02:07PM (#51447795)

    My grandmas are dead, you insensitive clod.

  • by Chas ( 5144 ) on Friday February 05, 2016 @03:22PM (#51448549) Homepage Journal

    DSL is high speed internet...

    And I stopped reading bullshit article right there...

  • Does 6mbps actually qualify as high-speed anymore ? I thought Congress/FCC decided it had to be like 50 mbps to be called high speed ?

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