The Telecom Digest for November 10, 2010
Volume 29 : Issue 303 : "text" Format
Messages in this Issue:
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Date: Tue, 9 Nov 2010 08:59:32 -0600
From: "Gray, Charles" <charles.gray@okstate.edu>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Why is T-1 24 Channels? (telecomm)
Message-ID: <18AC66D00A844644BF202001BCE0FE26405C6E0C06@STWEXE3.ad.okstate.edu>
See http://en.wikipedia.org/wiki/T-carrier for a good write-up. Essentially,
it says that Bell Labs started muxing channels together, and just added more
until the performance suffered, so they stopped at 24 channels.
Regards.
Charles G. Gray
Senior Lecturer, Information Technology
Oklahoma State University - Tulsa
(918) 594-8433
***** Moderator's Note *****
Sorry, that's not the real reason.
Bill Horne
Moderator
Date: Tue, 09 Nov 2010 10:56:13 -0800
From: Sam Spade <sam@coldmail.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Bell System Technical Journal, 1922-1983
Message-ID: <u92dnaiAw9DSBETRnZ2dnUVZ_hidnZ2d@giganews.com>
Hudson Leighton wrote:
> Bell System Technical Journal, 1922-1983
>
> With this posting of the Bell System Technical Journal from volume 1
> issue 1 in July 1922 to the final issue published in December 1983, we
> are pleased to be able to open the vault of this knowledge to our global
> technical colleagues.
>
> http://bstj.bell-labs.com/
>
> ***** Moderator's Note *****
>
> Yes, we've seen this before, but I couldn't resist the chance to play
> "Ultimate Telecom Trivia"!
>
> Here's the question: why does a T1 line have 24 channels?
>
> Bill Horne
> Moderator
>
Sampling rate and type of conductor?
The long haul stuff had 96 channels and a more sophisticated conductor.
***** Moderator's Note *****
Sorry, that's not it.
Bill Horne
Moderator
Date: Mon, 08 Nov 2010 23:23:17 -0500
From: tlvp <tPlOvUpBErLeLsEs@hotmail.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: iPhone vs. Android vs. BlackBerry
Message-ID: <op.vlvyg3reitl47o@acer250.gateway.2wire.net>
On Mon, 08 Nov 2010 15:56:52 -0500, after tlvp <tPlOvUpBErLeLsEs@hotmail.com>
wrote, Moderator Noted:
>
> Well, how about setting up a cottage industry. You get the guys in
> Guatemala, and charge 50% of the "repair" price people pay up here:
> you'll be rolling in dough.
Heh ... shipping there and back can be too flaky, costly, and time-consuming
to make that a viable venture. As it happened, I was just going to be there
anyway, hence took the handset along with me on spec ... and lucked out.
Shoulda' bought a spare battery while I was at it ... :-) .
Cheers, -- tlvp
--
Avant de repondre, jeter la poubelle, SVP
Date: Tue, 09 Nov 2010 16:21:47 +1100
From: David Clayton <dcstar@myrealbox.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Bell System Technical Journal, 1922-1983
Message-ID: <pan.2010.11.09.05.21.46.207913@myrealbox.com>
On Mon, 08 Nov 2010 15:39:24 -0600, Hudson Leighton wrote:
> Bell System Technical Journal, 1922-1983
>
> With this posting of the Bell System Technical Journal from volume 1 issue
> 1 in July 1922 to the final issue published in December 1983, we are
> pleased to be able to open the vault of this knowledge to our global
> technical colleagues.
>
> http://bstj.bell-labs.com/
>
> ***** Moderator's Note *****
>
> Yes, we've seen this before, but I couldn't resist the chance to play
> "Ultimate Telecom Trivia"!
>
> Here's the question: why does a T1 line have 24 channels?
>
Apart from fitting in the required quantity of voice channels and the
signalling?
A bit like the E1 with 30x64kbps voice channels and 128kb of signalling.
--
Regards, David.
David Clayton
Melbourne, Victoria, Australia.
Knowledge is a measure of how many answers you have, intelligence is a
measure of how many questions you have.
***** Moderator's Note *****
Sorry, that's not the reason.
Bill Horne
Moderator
Date: Tue, 09 Nov 2010 09:18:12 -0500
From: Eric Tappert <e.tappert.spamnot@worldnet.att.net>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Bell System Technical Journal, 1922-1983
Message-ID: <3plid6p64a81f6ebfco0crekpa65on62th@4ax.com>
On Mon, 08 Nov 2010 15:39:24 -0600, Hudson Leighton
<hudsonl@skypoint.com> wrote:
>Bell System Technical Journal, 1922-1983
>
>With this posting of the Bell System Technical Journal from volume 1
>issue 1 in July 1922 to the final issue published in December 1983, we
>are pleased to be able to open the vault of this knowledge to our global
>technical colleagues.
>
>http://bstj.bell-labs.com/
>
>***** Moderator's Note *****
>
>Yes, we've seen this before, but I couldn't resist the chance to play
>"Ultimate Telecom Trivia"!
>
>Here's the question: why does a T1 line have 24 channels?
>
>Bill Horne
>Moderator
Bill,
The standard multiplexing scheme in use when T1 carrier was introduced
was based on a 12 channel group. The digital line was known as a
"digroup", or two groups. The choice was made to facilitate
connection to the existing long haul analog network (a single DS- 1
bank to two group banks). European providers use a 30 channel system
(plus a framing and a signaling channel for a total of 32 timeslots)
instead of our 24 channel arrangement.
ET
--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
***** Moderator's Note *****
I'll be the first to admit I'm wrong if you can find those reasons in
the BSTJ, but I don't think that's the cause.
Bill Horne
Moderator
Date: Tue, 09 Nov 2010 15:24:50 -0600
From: bonomi@host122.r-bonomi.com (Robert Bonomi)
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Bell System Technical Journal, 1922-1983
Message-ID: <C-Sdne367rO_IUTRnZ2dnUVZ_hCdnZ2d@posted.nuvoxcommunications>
In article <hudsonl-B830BD.15392408112010@news.isp.giganews.com>,
>
>***** Moderator's Note *****
>
>Yes, we've seen this before, but I couldn't resist the chance to play
>"Ultimate Telecom Trivia"!
>
>Here's the question: why does a T1 line have 24 channels?
A) Somebody dyslexic was reading Douglas Adamms.
B) To replace a 25-pair trunk cable, where one pair is held out as a spare.
***** Moderator's Note *****
A. I don't think so, but he'd have loved it.
B. Trunk cables have thousands of pairs.
Any other contestants?
Bill Horne
Moderator
Date: Tue, 9 Nov 2010 07:08:08 -0500
From: T <kd1s.nospam@cox.nospam.net>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Happy anniversary cellphone!
Message-ID: <MPG.274303b3e97f4108989cff@news.eternal-september.org>
In article <e55cf.dc33c6c.39fa1e21@aol.com>, wesrock@aol.com says...
>
>
>
> In a message dated 10/27/2010 5:23:15 PM Central Daylight Time,
> johnl@iecc.com writes:
>
> >> 339-DOG-TITS. Beat that for being easy to remember!
> >
> > My 800 number spells my wife's name. I think that's why she
> > finally agreed to marry me.
>
> A reporter on our company (SWBell Oklahoma) employee newspaper went to
> Stillwater to do a story on the fall enrollment rush at the business
> office. (I believe the business office had a set up on the camous
> where students arrived.) They had a list of numbers they would not
> assign because of what they spelled. One of them spelled TITS. I
> don't remember some of the others.
>
>
> Wes Leatherock
> wesrock@aol.com
> wleathus@yahoo.com
Apparently as of the 1990's they didn't check too well, at least not in
NyNex territory. Friend of mine got 401-APE-COCK.
Date: Tue, 9 Nov 2010 20:17:13 +0000 (UTC)
From: moroney@world.std.spaamtrap.com (Michael Moroney)
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Camouflaged cellphone tower plans for Cupertino CA
Message-ID: <ibca89$j2$1@pcls6.std.com>
Sam Spade <sam@coldmail.com> writes:
>Thad Floryan wrote:
>> Despite the local Cupertino CA residents' fight against the deployment,
>> this is the first cellphone tower plan I've ever seen and I thought it
>> interesting to share with the group. Visiting the following URL will
>> bring up a 7-page, 2.2MB PDF of the proposed AT&T tower facility:
>>
>> http://cupertino.granicus.com/MetaViewer.php?view_id=14&clip_id=1037&meta_id=53189
>>
>This isn't the first of those "trees." They are so phony they stick out
>like a sore thumb.
There's one of those cell phone "trees" that is so bogus-looking that
my then-two year old daughter would always point out the "silly tree"
whenever we drove by it. Personally, I find it uglier than a
non-disguised tower would be.
I've heard them called "Frankenpines".
***** Moderator's Note *****
Ah, but I bet it's a thing of beauty to any FCC bureaucrat.
Bill Horne
Moderator
Date: Tue, 9 Nov 2010 14:13:11 -0500
From: "Michael D. Sullivan" <mds@camsul.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Bell System Technical Journal, 1922-1983
Message-ID: <AANLkTi=pMt6dhtqXiEbPCpMPWSS8mqXbtFv5ta9HhvGY@mail.gmail.com>
On Mon, 08 Nov 2010 15:39:24 -060, in
<hudsonl-B830BD.15392408112010@news.isp.giganews.com>, our moderator
asked:
>>***** Moderator's Note *****
>>Yes, we've seen this before, but I couldn't resist the chance to play
>>"Ultimate Telecom Trivia"!
>>Here's the question: why does a T1 line have 24 channels?
>>Bill Horne
>>Moderator
Because that's how many channels a "supergroup" had. (And presumably
how many twisted pairs were in the cable it replaced.)
--
Michael D. Sullivan
Bethesda, MD
***** Moderator's Note *****
Sorry, I think there's another reason.
Bill Horne
Moderator
Date: Tue, 9 Nov 2010 10:04:30 -0800 (PST)
From: Lisa or Jeff <hancock4@bbs.cpcn.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: MSNBC on text message spam
Message-ID: <e5da829c-5d17-4a91-9a1e-555c711b220f@z22g2000pri.googlegroups.com>
MSNBC had a report on text message spam, as using for debt
consolidating companies. They send out a "survey"* then go into a
sales pitch.
For article please see:
http://redtape.msnbc.com/2010/11/next-debt-help-nuisance-text-message-spam.html
IMNO, any kind of unsoliciting texting to cell phones ought to be
illegal** because many subscribers (like me) have to pay for each
text, and it disrupts legitimate messaging. I'm not sure what the
cell phone carriers are doing, if anything, to curtail spam texting.
(Is there anyone who thinks this sort of thing should be allowed? If
so, why?)
In response to my complaint my carrier said they could turn off
texting for my account, and I had them do so. I don't text so it
shouldn't have been a problem.
However, I discovered several problems with turning off my texting
capability. Basically, _everything_ is turned off, including legimate
things.
--No "bounce message": A few people who texted me (not knowing I
don't text) didn't know I had it turned off. They did not get any
rejection message as one gets with regular email and assumed I got
their text.
--No service messages or balance replies: I cannot receive legitimate
service messages from the carrier nor responses to inquiries about my
account usage and balance.
--Hurts unanswered messages: If someone calls me and I don't answer,
they get an option to leave a callback number. But that message does
not go through.
*I get a great many "survey" calls at home on my landline.
Technically these are legal and not affected by "do not call" lists.
I hang up immediately before I hear what it's about. Now I wonder if
some of those "surveys" are in actuality veiled sales pitches.
**I understand unsolicited voice calls to a cell phone are illegal
regardless of their nature. Fortunately I've only gotten one or two
of those. I believe unsolicited calls to nursing home residents are
also illegal, but my mother still got some of those. I suspect the
originators are using sequential automatic dialers that simply go
through every number.
Date: Tue, 09 Nov 2010 00:08:51 -0600
From: Neal McLain <nmclain@annsgarden.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Bell System Technical Journal, 1922-1983
Message-ID: <4CD8E573.6060408@annsgarden.com>
Bill Horne wrote:
> Yes, we've seen this before, but I couldn't resist the
> chance to play "Ultimate Telecom Trivia"! Here's the
> question: why does a T1 line have 24 channels?
Because:
- Each voice channel requires 4000 Hz bandwidth.
- Harry Nyquist tells us that the sampling rate must be twice the
highest frequency within that bandwidth, or 8000 Hz.
http://mathworld.wolfram.com/NyquistFrequency.html
- The circuit uses Pulse Code Modulation with a sampling rate of 128
steps, so 7 bits (plus one check bit) must be transmitted for each sample.
- Manholes in urban areas are about 6000 feet apart, which is the
distance between loading coils in a voice loop.
- Data repeaters have to be accessible for service (i.e., in manholes),
so they must be 6000 feet apart.
- The circuit must operate over No. 22 twisted pair.
- Research at Bell Labs in the 1960s showed that the maximum data rate
that could be reliably transmitted over a distance of 6000 feet over No.
22 conductors is about l.6 Mb/sec. Presumably, this research included
allowances for overspaced manholes, wet cable, corroded splices, ambient
temperature variations, and anything else that Murphy could dream up.
- Maximum permissible number of channels =
(1600000 bits/second) / (8000 samples/second/channel) / (8 bits/sample)
= 25 channels.
- Subtract one channel for overhead (framing and signaling) yields 24
channels.
Drive down a country road and you'll often see T1 repeaters about every
mile or so, either on posts or on poles.
http://www.annsgarden.com/poles/T1_Repeater1b.jpg
Now here's my trivia question: how many channels did the first cable TV
system carry?
Neal McLain
***** Moderator's Note *****
I don't think that's the reason. If you were one of the designers,
I'll bow to your expertise, but I have a far less technical
explanation in mind. And, no, it's not a joke.
Bill Horne
Moderator
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End of The Telecom Digest (11 messages)
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