29 Years of the Digest ... founded August 21, 1981
The Telecom Digest for April 09, 2011
====== 29 years of TELECOM Digest -- Founded August 21, 1981 ======
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Date: Thu, 7 Apr 2011 22:35:58 -0500 From: John Mayson <email@example.com> To: firstname.lastname@example.org. Subject: Re: Afghanistan does NOT have more cellular competition than the US Message-ID: <BANLkTi=CyY4rK-aS9mVD_1acPKX_ofqPjQ@mail.gmail.com> On Thu, Apr 7, 2011 at 10:20 PM, Bob Goudreau <BobGoudreau@nc.rr.com> wrote: > > And my town has about 1/2000th of the US population, but it also has four > major cellular providers: AT&T, Sprint, T-Mobile and Verizon. So what? > > Comparing the number of wireless networks to national population is a red > herring. What matters is the number of carriers competing with each other > for any given individual's business. China and India each have about 1000 > times the population of Estonia or Timor Leste, but no one expects either I think reality lies somewhere in between. You're right, the per capita number of providers doesn't necessarily equal more competition. I do think more is better and we're moving in the wrong direction with the AT&T/T-Mobile deal. To have true competition in the US we would need complete interoperability (i.e. all providers work off the same standard) and the freedom to take the phones we outright own across the street to another provider. Providers can take some solace in knowing we're locked into two-year contracts and there's little danger of customers moving on a whim. And when we do move we generally have to buy a new phone. I have personally taken a phone from T-Mobile to AT&T, but I'm a phone geek. Not too many people know how to do that or even realize it can be done. I got blank stares at the AT&T store and had to explain to them it would work. I don't buy the "we need to extra bandwidth" issue that AT&T is giving. Yeah, they will have more spectrum, but legacy T-Mobile customers are using that spectrum. Again, going back to having a single standard, the cell phone companies could share infrastructure which reduces their costs and benefits the consumer. The move is about knocking out a competitor. Sorry, I'll get off my "we need a single standard" soapbox at some point this century. :-) John -- John Mayson <email@example.com> Austin, Texas, USA
Date: Fri, 8 Apr 2011 11:41:28 -0400 From: "Jim Bennett" <firstname.lastname@example.org> To: email@example.com. Subject: Re: Does FiOS support rotary phones? Message-ID: <000501cbf603$6ffb0e10$01fea8c0@dell8100> Bill [our moderator] asked: > Why were Autovon phones designed for four wire connections? The short answer is that they didn't have to be four-wire. Many subscriber sets connected to the Autovon network were ordinary two-wire phones, connected to a PBX or through Centrex lines to a local switching center, which then connected to the Autovon network through special, dedicated trunk interfaces. The long answer includes some facts and a bit of conjecture. A subscriber set that connected directly to an Autovon switch was indeed a four-wire instrument, with a different internal network in the phone [lacking the "hybrid" transformer arrangement found in a typical POTS phone]. The standard explanation for this is that these subscribers were located a long distance from the Autovon switch, and the trunks were four-wire for the same reasons that all long-distance circuits have a separate transmit and receive path, i.e., the need for carrier systems and/or repeaters, which are easier to design and build when they do not have to be bi-directional [which they would need to be on a single pair], and the issue of echo cancellation [a huge problem on a long single-pair trunk]. Additional premise equipment was needed at a subscriber location in order to connect directly to an Autovon switch. In addition to the signaling system needed to place calls over a trunk [they used SF, and, on shorter circuits, DX signaling on a separate E&M pair], there was also a special interface required to handle call priority.  But now the answer gets even longer: The Autovon switches themselves are [were] referred to in the available literature as "four wire switches." Indeed, the crossbar switches originally used were in fact modified, and the 1AESS that replaced crossbar in Autovon was also a "special," with very different programming from a standard ESS. Much of the differences had to do with the actual route selection matrix, which was remarkably complex and could re-route circuits to bypass switching nodes and circuit paths that were down. This concept will likely sound quite familiar today - it is, of course, part of the basis of how the internet works. DARPA simply built on decades of existing developments that were all driven by the impetus of the Cold War. It is this reference to "four-wire switches" that leads to the conjecture that makes this answer so long. While I cannot produce any documentation to prove this, it has always been my belief that Autovon switches had the ability to treat the transmit and receive paths of a telephone call as completely separate circuits. In an ordinary toll switch, the two circuits that carry to two sides of a conversation are always handled and switched together as a unit, and will both travel over the same physical route. I will leave it as an exercise to the reader to conclude why the Autovon system would wish to treat the transmit and receive pairs [and their long-haul circuit routes] as distinctly separate. Officially, however, Autovon was always described as a "non-secure" system, and was [supposedly] never intended to carry "top secret" conversations. Proving [or disproving] any or all of this theory could be a challenge: While Autovon has been out of service for almost two decades, much of the official documentation regarding its operation remains classified to this day. On his website, "A Secert Landscape," Albert LaFrance has copies of two lists of Autovon related documents that were furnished by the DoD's DTIC [Defense Technical Information Center] in response to a Freedom of Information Act request. The first is the list of documents that have been "approved for public release," and it runs about fifty pages. The second list, which contains those documents that remain classified ["distribution restricted" in DoD-speak] runs some two hundred pages. Bill continued: > Were the "Digital Non-Secure Voice Terminals" actually ISDN sets?. > Are any of the switchboards or other systems that these phones > connected to available on the surplus market? I'm not looking to > take over Radar O'Reilly's job, but I wonder if these "DNSVT" units > connected to the equivalent of a small-business PBX. As you know, ISDN does not actually specify a physical circuit type, but I assume that you are referring to a typical ISDN phone in North America, which connects to the CO over a four-wire circuit [two 64 kbps channels, one transmit and one receive], essentially a single DS0 encoded using 2B1Q. The Digital Voice Terminal field phones used by the Army actually used a 16 kbps CVSD [Continuously Variable Slope Delta] coding technique for the actual talk path, and 16 or 32 bit conditioned diphase [sometimes called "differential Manchester encoding"] for call set-up and signaling. Some commercially available electronic key systems use CVSD for the talk path, and when this question came up a couple of years back on a popular interconnect forum, I questioned whether such a key system could be adapted to work with these phones. About a year after the thread first ran, an Army Signal Corps veteran posted to describe what was actually required to connect one of these phones to the PSTN: In addition to converting the talk path, you must of course also interface the call setup and signaling, and based on this person's comments it seems that there is no easy way to do this without the actual equipment used by the Service. As far as whether this equipment is available on the surplus market, that is an excellent question. As you know, surfing the global internets using our favorite search engine reveals that many of the common search terms for this sort of thing have been usurped by "content farm" sites and others that have nothing to do with Military phones, and exist only to try and sell you something completely unrelated [insert long sigh here]. If anyone knows of any legitimate surplus dealers that carry this equipment at a reasonable price, please let us all know! Bill also asked: > Are repairs or parts available for any of the more recent models? The best bet for repair parts for any Military phone is to cannibalize an identical unit. This is why it never hurts to buy one that is battered and incomplete, if the price is right and you have [or will have] a "good" one. In addition to ebay and actual surplus dealers, this equipment and parts for it often turn up at Ham shows, "old-school" computer shows, and even shows for Military vehicle collectors. I don't know of anyone that offers repairs for this equipment, but they may exist, so again I would ask that if anyone knows of them, please let us all know. And now, [drum roll, please] the end notes:  For an example of the additional premise equipment required to connect directly to an Autovon switching center, see BSP 981-210-100 [if the following is split into two lines, you may need to paste them into a text editor and splice it back together to use the link]: http://sc.infc.info/index.php?option=com_docman&task=doc_details&gid=3478&Itemid=2  "A Secret Landscape" is found at: http://coldwar-c4i.net/ . Also see Albert's other excellent site: http://long-lines.net/ .  This will come as no surprise to anyone who has ever looked for certain info regarding telecom and the Armed Services, as the DoD has always played it very close to the vest in this area. Some people may be amazed to discover that they can find a manual for their new mil-surplus machine gun in about 30 seconds, but days of searching can't turn up a manual for their ancient field phone. For example, the TA-1 phone is basically a butt-set with a built in magneto and a dynamic [sound powered] transmitter element. It is considered an antique now, but the manual for it remains "restricted" to this day. I keep mine locked in the safe, next to the launch codes. ;) Jim Bennett ************************************************** Speaking from a secure undisclosed location.
Date: Fri, 08 Apr 2011 11:31:36 -0500 From: firstname.lastname@example.org (Robert Bonomi) To: email@example.com. Subject: Re: Does FiOS support rotary phones? Message-ID: <v9adncd1uMX1pQLQnZ2dnUVZ_rqdnZ2d@posted.nuvoxcommunications> In article <000501cbf52c$7ab353d0$01fea8c0@dell8100>, > >***** Moderator's Note ***** > >Jim, I appreciate the info. I'll check out the phones you mentioned, >and maybe even get one for a conversation piece. > >Please answer these questions for me and the other readers: > >1. Why were Autovan phones designed for four wire connections? This one I can contribute on: (There were separate pairs for tx and rx, obviously, thus --) no need for echo cancellers on long circuits. easier interface to radio links. better control of signal levels -- very useful for multi-party calls.
Date: Fri, 08 Apr 2011 15:45:13 -0700 From: Sam Spade <firstname.lastname@example.org> To: email@example.com. Subject: Re: Cut Your Telecom Bills Message-ID: <Mrqdnd_zt-FnEgLQnZ2dnUVZ_jKdnZ2d@giganews.com> Bill Horne wrote: > There is a good article called "Cut your telecom bills" in the May, > 2011 issue of Consumer Reports magazine. > > There are several parts of it that caught my eye right away: a section > titled "Some fiber really isn't", covering some of the physical-layer > issues we've been discussing here, and a section on the "Ooma" VoIP > service, plus a section on "The benefits of bundling and bargaining". > > I'm curious what the Digest's readers think about the article. > > Bill > The glaring omission for me was their failure to mention how robust and reliable E911 is with a wireline carrier, and how 911 wireless or 911 Voip can be problematic at a residence.
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