30 Years of the Digest ... founded August 21, 1981
The Telecom Digest for August 17, 2011
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Date: Fri, 16 Sep 2011 06:54:55 -0700 (PDT) From: Wes Leatherock
To: firstname.lastname@example.org. Subject: Re: EXchanges (was: area code named beer) Message-ID: <1316181295.50485.YahooMailClassic@web111702.mail.gq1.yahoo.com> --- On Thu, 9/15/11, Thor Lancelot Simon wrote: > HAncock4~ > wrote: > >On Sep 13, 7:46~am, Neal McLain > wrote: > > > >As an aside, in some cases NYC had _8_ digit phone > numbers, such as > >HOllis 5-10254.~ A manual exchange could have > 10,500 numbers.~~~Also, > What happened to these numbers when long distance direct dialing was > implemented? Were they really all renumbered? >> was dialed, too. Literature on the panel exchange in NYC >> confirms the registers could hold and pass 8 digits. I don't >> know if that applied in other big cities. > "The" panel exchange? > I don't disbelieve this but I would certainly like to see some > references. I remember reading about this many years ago, probably in Bell Labs Record at the time. The devices at the manual end offices were called Panel Call Indicators (PCI). Somewhere I remember one of the illustraions was of the ir use in New Orleans, in addition to NYC, of course. I have no information on 8-digit numbers or party line suffixes, except to note that party line suffixes were very common in manual offices of all sizes, including magneto exchanges. Wes Leatherock email@example.com firstname.lastname@example.org
Date: Fri, 16 Sep 2011 15:08:31 -0400 From: Fred Goldstein
To: email@example.com. Subject: Re: Looks like the "LightSquare" deal is hitting some potholes Message-ID: <20110916190830.27B8D57C9@mailout.easydns.com> On >Thu, 15 Sep 2011 13:03:32 -0400, danny burstein wrote, > >Background: "LightSquared" has been pushing for using so-called >"spare" radio frequency space for data and other wireless projects. > >Current licensees are, for the most part, against it, partly >because of the added competition (natch), but also because >it looks like there are some pretty serious interference isssues. Boy, that Right Wing Echo Machine has been making up some weird stuff. Let's recap. (And I did read the lengthy report to the FCC that was filed last month as part of the proceeding.) LightSquared has nothing to do with "spare" frequenies, like the White Spaces on the TV band. It's all about satellite frequencies to which they hold the licenses. Lightsquared, formerly SkyTerra, is the licensee of L-band mobile satellite frequencies in the 1.5 GHz range. Around 2003, the FCC authorized Ancillary Terrestrial Component operation, which means that they can put earth-based base stations on satellite frequencies, not just use satellites. Originally this was meant to fill in coverage shadows, as in cities where buildings blocked the view of the birds. But later, the FCC allowed ATC to be used on a more primary basis, with handsets that did not also have satellite coverage. That's the controversy. Lightsquared's satellite frequencies are just below those used by civilian GPS. When their only transmitters were in the sky, this was no problem. But ATC means that there are high-powered transmitters on the ground, so if you're near one, you get a strong signal. Bear in mind that ATC has been authorized for years... GPS receiver manufacturers, however, noted that there were no ATCs in use, so they saved a little money (ahem) by not making their wares resistant to nearby-frequency signals. Not that it's impossible; it just costs a little. As GPS got more common, it often followed the declining price-quality curve characteristic of Chinese mass production. So now there are a bazillion GPS receivers that were built without the ability to withstand ATC on nearby frequencies. And LightSquared wants to build a new network. Some on the FCC like this because it provides just a bit more competition, as the mobile business otherwise consolidates, and doesn't involve more auctions (which would almost always go to the big two incumbents, since it's worth more to ATT and VZ to keep out competition than it is for a new operator to compete, the public be damnedd). Sprint likes this because they could use partners. But of course the GPS industry and its customers don't want to lose service. Hence the repeated studies. Now let's get a bit more technical. LightSquared has two 10 MHz bands to work with, one just below GPS and one about 30 MHz below that. Their study (with lots of test documentation) shows that the lower band does not cause interference to almost any consumer GPS, but the upper band does. So they offered to revise their plan and to only use the lower band for at least a few years, giving ample warning to the industry before turning on the upper band. In this week's revision, they've further offered to lower their signal strength by 6 dB for an interim period. There is one more angle here, the high-precision augmented GPS. This uses a second signal from commercial satellites, and is used for stuff like farm tractors and mining. (Military is separate. Aviation doesn't use this augmentation.) LightSquared and Inmarsat are the satellite providers. This uses their lower 10 MHz band. LightSquared has offered to pay every user of this signal to modify their receivers (a few hundred thousand of them) to use a different frequency. I don't recall if Inmarsat receivers are impacted too but LightSquared has offered to cover that cost too. So if LightSquared goes ahead there is a small risk that in the short term, some really grody GPS receivers will get interference in a few locations. If they get to use the upper band, then a lot more receivers will get interference, but the hope (a bit unrealistic, perhaps) is that they will mostly be replaced by then, and the GPS vendors will be on notice. But the vendors would rather shave a nickel off of their front end costs. And to the Banana Republican politicians, who only care about making Obama look bad regardless of the facts, it's just another talking point. -- Fred Goldstein k1io fgoldstein "at" ionary.com ionary Consulting http://www.ionary.com/ +1 617 795 2701
Date: Fri, 16 Sep 2011 07:24:37 -0700 (PDT) From: HAncock4
To: firstname.lastname@example.org. Subject: Re: EXchanges (was: area code named beer) Message-ID: <email@example.com> On Sep 16, 12:18 am, t...@panix.com (Thor Lancelot Simon) wrote: > >As an aside, in some cases NYC had _8_ digit phone numbers, such as > >HOllis 5-10254. A manual exchange could have 10,500 numbers. > > What happened to these numbers when long distance direct dialing was > implemented? Were they really all renumbered? DDD required that all subscribers have a uniform ten digit number-- three digit area code and seven digit local number. In 1950 a great many subscribers in smaller towns and cities had phone numers with three, four, five, or six digits, and all had to be converted to seven digits. This was a major undertaking that took years to complete. Those subscribers with an eight digit number, be it 2L-6N or a party line suffix, also had to get new numbers. >> ...was dialed, too. Literature on the panel exchange in NYC >> confirms the registers could hold and pass 8 digits. I don't know >> if that applied in other big cities. >" The" panel exchange? I >> don't disbelieve this but I would certainly like to see some >> references. The Bell Labs history volume 1 (op cit) mentions that manual exchanges had the capacity for 10,500 digits. Also, they show the interface panel for the inward B operator having eight digit capacity, either the leading 1 or a party-line suffix. Around 1930, New York Telephone prepared a booklet from a lecture describing the panel exchange in use in NYC, and this also notes the eight digits. Unfortunately, I don't have a title nor know how it can be found on-line. I've heard that NYC phone books circa 1950 had listings showing eight digits. Some day I hope to visit a NYC library and look up such a book (they do have them); I'm particularly curious to see the dialing instructions. There were classified ads in the NYT of that era showed an eight digit number.
Date: Fri, 16 Sep 2011 23:15:38 +0000 (UTC) From: firstname.lastname@example.org (Thor Lancelot Simon) To: email@example.com. Subject: Re: EXchanges (was: area code named beer) Message-ID:
In article <firstname.lastname@example.org>, HAncock4 wrote: >On Sep 16, 12:18 am, t...@panix.com (Thor Lancelot Simon) wrote: > >> >As an aside, in some cases NYC had _8_ digit phone numbers, such as >> >HOllis 5-10254. A manual exchange could have 10,500 numbers. >> >> What happened to these numbers when long distance direct dialing was >> implemented? Were they really all renumbered? > >DDD required that all subscribers have a uniform ten digit number-- >three digit area code and seven digit local number. In 1950 a great >many subscribers in smaller towns and cities had phone numers with >three, four, five, or six digits, and all had to be converted to seven >digits. This was a major undertaking that took years to complete. Not such a major undertaking. In roughly 1980 I lived in a rural area of New York State that still had 4 digit dialing. Extension to a _longer_ number can be done automatically -- it is fully deterministic, you are just adding predetermined digits. My number was 687-XXXX for external purposes, but for in-town callers, simply XXXX would do. The "687", obviously, was just added onto the front when numbers went to 7 digits -- and there were towns near us with switches still configured to allow 3-digit dialing, which had had four digits prefixed to the front, too. However, there is no such mapping from longer numbers (8 digits) onto shorter numbers (7 digits). Since New York City got only one area code in the original direct-dial plan, if there were really 8 digit numbers in circulation, some subscribers' numbers would have had to be completely changed, not just extended. This is what I am a little skeptical about. -- Thor Lancelot Simon email@example.com "All of my opinions are consistent, but I cannot present them all at once." -Jean-Jacques Rousseau, On The Social Contract
Date: Fri, 16 Sep 2011 18:57:33 -0700 (PDT) From: HAncock4
To: firstname.lastname@example.org. Subject: Re: EXchanges (was: area code named beer) Message-ID: On Sep 16, 10:24~am, HAncock4 wrote: > DDD required that all subscribers have a uniform ten digit number-- > three digit area code and seven digit local number. ~In 1950 a great > many subscribers in smaller towns and cities had phone numers with > three, four, five, or six digits, and all had to be converted to seven > digits. ~This was a major undertaking that took years to complete. P.S. Many times the "conversion" was accomplished at the same time a town was converted from manual to dial, which was a major effort in those years. Subscribers had to get used to a new phone number and billing routing records had to be all changed, but there was no equipment modification. However, towns that were already dial had to be converted to be 7D. In step-by-step offices this often meant adding a "digit absorbing" selector. Say a town had five digit numbers, 5-xxxx and 6-xxxx and the town was to become 345-xxxx and 346-xxxx. The switch would simply absorb the initial 3 and 4. This meant that people within the town would continue dialing five digits as they did before, only outsiders needed all seven. In many small towns in isolated areas five digit dialing continued well into the 1970s. It ended when more exchanges were added as population grew. I don't have any statistics, but I suspect DDD was not offered very widely in the 1950s because the company was too busy expanding toll line capacity and converting local exchanges to dial. I _think_ the Bell System was about 50% dial at the end of WW II, not sure of the percentage in 1960. Anyway, the first step in providing DDD was to providing operator direct dialing, which sped up call handling. That meant adding toll trunk signalling systems for ringing and supervision which was an effort in itself. (That signalling protocol would be compromised later on by the "blue boxes".) Even in the 1980s with DDD and TSP widespread, from time to time operators still 'built up' toll calls by calling intermediate toll centers and establishing the connection the old fashioned way. Likewise, they also wrote charge tickets instead of AMA. Other local exchange items that were necessary to provide DDD were increasing the sender length in #1 crossbar and panel exchanges to hold 10 digits, providing an 'exit' link in step by step exchanges, and providing AMA (automatic message accounting) with automated or operator calling number identification (ANI or ONI). AMA was installed either in the local exchange or at a tandem or toll switching office. Would anyone care to comment on how all this stuff is handled by modern exchanges today? Can a long distance company operator still "build up" a call manually? Are there still long distance company network managers watching their system for overloads and problems? Is there still a big AT&T network control center in Bedminster? Thanks. [public replies, please]
Date: Fri, 16 Sep 2011 17:18:53 -0700 (PDT) From: mattrix
To: email@example.com. Subject: Re: ANCIENT telephone transmission Message-ID: So much for my "Historian", On Sep 16, 10:58~am, Jim Haynes wrote: > "George O. Squier...was the inventor...in 1910, of telephone > carrier multiplexing... Thankyou Jim. by 1914 development of a commercial system > was underway." > > "By fall 1914 an experimental vacuum-tube-based carrier-multiplexed > telephone system carrying two simultaneous signals over a single circuit > had been set up in the laboratory of R. A. Heising." Suggesting that the original didn't use active components. >> - Without amplifiers, how do you handle attenuation? Turns out that the problem was phase distortion, more than attenuation. (I need to study transmission lines :) I'm still not sure how signalling worked. The US seems to have sent tones in the voiceband that could be recovered as signals? But I'm not sure if they did the same in Australia. In fact, after automatic exchanges were introduced (especially in the Step-by-Step system used in Australia), when did it become possible for the subscriber to make inter-exchange calls (say from one side of a city to the other) without operator intervention? How did the signalling work in that situation?
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