POTS line quality help
in [Design]
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From: Robert Baer on 24 Apr 2010 15:17 Kevin McMurtrie wrote: > In article <8rydnVl-iPND7U_WnZ2dnUVZ_v-dnZ2d(a)posted.localnet>, > Robert Baer <robertbaer(a)localnet.com> wrote: > >> krw(a)att.bizzzzzzzzzzzz wrote: >>> On Fri, 23 Apr 2010 20:01:41 -0700, Robert Baer <robertbaer(a)localnet.com> >>> wrote: >>> >>>> krw(a)att.bizzzzzzzzzzzz wrote: >>>>> On Thu, 22 Apr 2010 23:11:34 -0700, Robert Baer <robertbaer(a)localnet.com> >>>>> wrote: >>>>> >>>>>> Kevin McMurtrie wrote: >>>>>>> In article <k-adncl-GNqppFPWnZ2dnUVZ_ridnZ2d(a)posted.localnet>, >>>>>>> Robert Baer <robertbaer(a)localnet.com> wrote: >>>>>>> >>>>>>>> Once upon a time, a long time ago, there was only analog modems and >>>>>>>> nice paper manuals came with them. >>>>>>>> Some of those manuals, in the back discussed that for best use, one >>>>>>>> should order a specific quality of phone line and disclosed the BELLCO >>>>>>>> designation to use when ordering the line. >>>>>>>> As i remember it, that designation was something simple like >>>>>>>> (making >>>>>>>> this up) Z9. >>>>>>>> I think that the TekCom modem manual at that time was one that gave >>>>>>>> that info. >>>>>>>> Question: What is that designation? >>>>>>>> Thanks. >>>>>>> Cat 3 is commonly used for high quality telephone wiring. >>>>>>> >>>>>>> POTS is expected to go the way of the dinosaur within the next decade. >>>>>>> I'm ditching it as soon as my Internet gets a bit faster. New homes >>>>>>> are >>>>>>> wired with Cat 6 so the phone jacks may carry gigabit ethernet later. >>>>>> Ma Bell did not use Cat 3; there was no such thing in those daze and >>>>>> their designation of (POTS since that is all that existed then) their >>>>>> lines was (as i indicated) rather simple (and different). >>>>> Ma didn't, but pop often wired his house with Cat 3. Now all that stuff >>>>> is so >>>>> cheap there isn't any reason not to use a single pair of Cat 6s for >>>>> home-run >>>>> telephone wiring. >>>> So...i should buy about 20 miles of Cat 3 to run from the house to >>>> the CO? >>>> And make all the phone company, police, etc allow _that_?? >>> That was *not* the point made. >> The "point" is that you apparently do not know what you are talking >> about; i ask about bell designation for phone line quality and you >> mumble about Cat 3; not related in the slightest degree. > > You didn't originally mention that you wanted to know about utility pole > wiring. From what I've seen there is no standard cabling. Check some > old poles where the wiring has been cut and moved. The cable build > probably varies every block. > > Maybe you're thinking of fancy wiring that was used for long distance > calls before they were converted to digital signals. Correct; i made no mention or even allusion regarding utility pole wiring or even phone line wiring in general. As far as i am concerned, that is not relevant as even in the early 1980s, one could use a modem to communicate up to 28Kbaud if you had the money for those rather expensive (then) modems; all one had to do "extra" is to ask for a line selected for data service by way of their unique designation (T-1?). As communication technology improved and costs went down, one could (theoretically AND advertised) go to 56Kbaud (or was the lie "to 58K"). But some kind of stupid BS, that advertised rate was available on only ONE direction, a (slightly, sort of) slower rate in the other direction. I would not be surprised to learn, that in phone companies lust for money coupled with their UN-care for customers that NOBODY in the continental US can use POTS even at 33Kbaud.
From: Paul Keinanen on 24 Apr 2010 16:11 On Sat, 24 Apr 2010 12:17:53 -0700, Robert Baer <robertbaer(a)localnet.com> wrote: > As communication technology improved and costs went down, one could >(theoretically AND advertised) go to 56Kbaud (or was the lie "to 58K"). > But some kind of stupid BS, that advertised rate was available on >only ONE direction, a (slightly, sort of) slower rate in the other >direction. I do not what US advertisement claimed, but 56k technology assumed that the only analog path was the path between the phone office and the customer. The phone office produced 256 signal levels at 64 kbits/s and the end user modem had to determine which of these levels was actually transmitted. This required an A/D converter with more than 8 bits. The problem is much worse than this due to the A/u-law floating point format used in telephones, so in practice more than 12 bit linear ADCs are required in the downlink direction. In the uplink direction, there is no way that an phone office 8 bit A/D converter would be able to handle much more than 32k.
From: Robert Baer on 24 Apr 2010 19:25 Paul Keinanen wrote: > On Sat, 24 Apr 2010 12:17:53 -0700, Robert Baer > <robertbaer(a)localnet.com> wrote: > >> As communication technology improved and costs went down, one could >> (theoretically AND advertised) go to 56Kbaud (or was the lie "to 58K"). >> But some kind of stupid BS, that advertised rate was available on >> only ONE direction, a (slightly, sort of) slower rate in the other >> direction. > > I do not what US advertisement claimed, but 56k technology assumed > that the only analog path was the path between the phone office and > the customer. The phone office produced 256 signal levels at 64 > kbits/s and the end user modem had to determine which of these levels > was actually transmitted. > > This required an A/D converter with more than 8 bits. The problem is > much worse than this due to the A/u-law floating point format used in > telephones, so in practice more than 12 bit linear ADCs are required > in the downlink direction. > > In the uplink direction, there is no way that an phone office 8 bit > A/D converter would be able to handle much more than 32k. > > Hmm..maybe that was the reason for non-symmetrical communication rates; roughly 50K uplink and 56K downlink. Still....that is a damn sight more than the 28.8K i was getting up to last week and i would settle for the "original" 48.8K throttled speed.
From: krw on 24 Apr 2010 21:41 On Sat, 24 Apr 2010 15:25:46 -0800, Robert Baer <robertbaer(a)localnet.com> wrote: >Paul Keinanen wrote: >> On Sat, 24 Apr 2010 12:17:53 -0700, Robert Baer >> <robertbaer(a)localnet.com> wrote: >> >>> As communication technology improved and costs went down, one could >>> (theoretically AND advertised) go to 56Kbaud (or was the lie "to 58K"). >>> But some kind of stupid BS, that advertised rate was available on >>> only ONE direction, a (slightly, sort of) slower rate in the other >>> direction. >> >> I do not what US advertisement claimed, but 56k technology assumed >> that the only analog path was the path between the phone office and >> the customer. The phone office produced 256 signal levels at 64 >> kbits/s and the end user modem had to determine which of these levels >> was actually transmitted. >> >> This required an A/D converter with more than 8 bits. The problem is >> much worse than this due to the A/u-law floating point format used in >> telephones, so in practice more than 12 bit linear ADCs are required >> in the downlink direction. >> >> In the uplink direction, there is no way that an phone office 8 bit >> A/D converter would be able to handle much more than 32k. >> >> > Hmm..maybe that was the reason for non-symmetrical communication >rates; roughly 50K uplink and 56K downlink. > Still....that is a damn sight more than the 28.8K i was getting up to >last week and i would settle for the "original" 48.8K throttled speed. Sounds like they added a line to your neighborhood and stole part of your circuit (that they never promised you). You might see if you can find someone in the telephone company who can look up your circuit to see what happened.
From: miso on 24 Apr 2010 22:04
On Apr 24, 12:06 pm, Robert Baer <robertb...(a)localnet.com> wrote: > JosephKK wrote: > > On Tue, 20 Apr 2010 16:29:17 -0700, Robert Baer <robertb...(a)localnet.com> > > wrote: > > >> Once upon a time, a long time ago, there was only analog modems and > >> nice paper manuals came with them. > >> Some of those manuals, in the back discussed that for best use, one > >> should order a specific quality of phone line and disclosed the BELLCO > >> designation to use when ordering the line. > >> As i remember it, that designation was something simple like (making > >> this up) Z9. > >> I think that the TekCom modem manual at that time was one that gave > >> that info. > >> Question: What is that designation? > >> Thanks. > > > The last i heard you wanted a 3002 line. Should be able to provide 56k > > on typical current modems. > > THANK YOU!!!!! > I will see if that works here with Qwest in as much as they are > rather customer hostile; they only want money and care less about > anything else. > You make a call and find the line busy; an *automated* voice prompts > "for _only_ eightyfive cents we will try your call for later delivery" > (price something like that) Never Mind that it _costs_ them NOTHING to > do this; it is a way of extracting money from captive customers. > I could cite a fair number of other examples like the phone line > problem i have. > Up to about 6 months ago (roughly) i could reliably connect at 45K to > 48+Kbaud and then all of a sudden i got 28.8Kbaud and now am at 26.4K > and who knows how more it will sink? > The have been actively pushing DSL like crazy (3-5 inserts in monthly > bills, newspaper ads, etc) and PURPOSELY choking modem bandwidth to > "force" a change in $pending (= = ca$h to them). > Too bad the internet does not connect by way of semaphore flags... I'm baffled why anyone would use dial up. Somewhere in my paper documents I should have tossed (and might already have), I have the frequency responses from the old AEA phone line simulator. I had a tech run the spectrum analyzer on every line prior to designing a proprietary filter for (gasp) 2400bps. I don't recall the designators, but it should be documented in some dusty corner of an old Bell manual. The problem you have with a 56k modem is the fallback modes are intentionally crappy. What you would do in a modem design is throw the kitchen sink at doing the best possible performance on the top speed of the modem, and then do a minimal job on the fallback modes because they were just to have a check off on the datasheet. I was at Excess Solutions (Milpitas CA) today and they have two Rockwell 56k modems on the shelf for some crazy price like $15 each. In Silicon Valley, they are worthless. But if you had to use dial up in the boonies, I'd be using Rockwell gear. They always made the best modems. [I worked for the competition, so trust me on this one. We never could meet their specs.] The fallback modes on Rockwell gear were great. You paid for such performance dearly. I remember when we bought the AEA phone line simulator. It was about $20k in the early 80s. In the 90's, I saw it at RA Surplus for $200. |