29 Years of the Digest ... founded August 21, 1981
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The Telecom Digest for May 13, 2011
Volume 30 : Issue 120 : "text" Format
====== 29 years of TELECOM Digest -- Founded August 21, 1981 ====== |
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Date: Wed, 11 May 2011 22:27:04 -0600
From: Reed <reedh@rmi.net>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: History Early Data transmission technical considerations
Message-ID: <df2dnXv0a48w_FbQnZ2dnUVZ_sOdnZ2d@earthlink.com>
On 5/11/11 4:51 PM, Robert Bonomi wrote:
> In article<E_ydndNE-PZOd1TQnZ2dnUVZ_oGdnZ2d@earthlink.com>,
> Reed<reedh@rmi.net> wrote:
>> On 5/10/11 1:33 PM, Lisa or Jeff wrote:
>>> An article in the November 1957 discusses the technical issues in the
>>> speed and accuracy of data transmission over private lines. It
>>> recognizes that the telephone network was built for voice, not data.
>>> Various modulating and carrier modes are considered such as "AM double
>>> sideband" and "frequency shift transmission". 1600 bits per second
>>> was deemed a good speed at that time. (and the term "bit" was used
>>> then.) Line noise, delay distortion, and required terminal equipment
>>> were critical issues that needed to be addressed. The article gets
>>> quite technical.
>>>
>>> http://www.alcatel-lucent.com/bstj/vol36-1957/articles/bstj36-6-1451.pdf
>>>
>>
>> The term "bit" still describes the speed of the raw "data transmission
>> over private lines".
>
> Sometimes "yes", sometimes "no".
>
> Consider analog line signalling where one 'symbol' represents multiple
> 'bits' in the original data stream.
>
> Thus the 'classical' distinction between 'bits' and 'baud' in more commplex
> analog data links.
>
> For an extreme case, consider the Telebit Corp "PEP" protocol, used in
> their 'trailblazer' (and compatible) modems.
>
Well, yes, various methods have been used to increase the usable bit
rate of an otherwise band-limited channel. QAM, Trellis coding, etc.
However I think the the usable "speed" of the channel would still be
expressed in bits per second.
Also I took "L or J's" comment as aimed at bytes, etc. Perhaps they
meant baud, since that always has been a common point of
mis-understanding when speaking of modem speeds.
Thanks for the reminder, Reed
Date: 12 May 2011 09:27:35 -0400
From: kludge@panix.com (Scott Dorsey)
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: History Early Data transmission technical considerations
Message-ID: <iqgn87$il$1@panix2.panix.com>
Reed <reedh@rmi.net> wrote:
>
>Well, yes, various methods have been used to increase the usable bit
>rate of an otherwise band-limited channel. QAM, Trellis coding, etc.
>However I think the the usable "speed" of the channel would still be
>expressed in bits per second.
http://en.wikipedia.org/wiki/Shannon-Hartley_theorem
The word "bit" actually comes from Nyquist back in the twenties, but the
actual relationship between channel capacity in bps, bandwidth, and noise,
was worked out by Shannon in 1948.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Date: Thu, 12 May 2011 20:59:15 -0400
From: ajbcommconsulting@frontier.com (Jim Bennett)
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: History Early Data transmission technical considerations
Message-ID: <4DCC8263.60106@frontier.com>
On 2011-05-12 00:27, Reed wrote:
> On 5/11/11 4:51 PM, Robert Bonomi wrote:
>> In article<E_ydndNE-PZOd1TQnZ2dnUVZ_oGdnZ2d@earthlink.com>,
>> Reed<reedh@rmi.net> wrote:
>>> The term "bit" still describes the speed of the raw "data transmission
>>> over private lines".
>>
>> Sometimes "yes", sometimes "no".
>>
>> Consider analog line signalling where one 'symbol' represents multiple
>> 'bits' in the original data stream.
>>
>> Thus the 'classical' distinction between 'bits' and 'baud' in more
>> commplex
>> analog data links.
>>
>> For an extreme case, consider the Telebit Corp "PEP" protocol, used in
>> their 'trailblazer' (and compatible) modems.
>>
>
> Well, yes, various methods have been used to increase the usable bit
> rate of an otherwise band-limited channel. QAM, Trellis coding, etc.
> However I think the the usable "speed" of the channel would still be
> expressed in bits per second.
>
> Also I took "L or J's" comment as aimed at bytes, etc. Perhaps they
> meant baud, since that always has been a common point of
> mis-understanding when speaking of modem speeds.
>
> Thanks for the reminder, Reed
>
>
Actually, I believe that Lisa and/or Jeff were pointing out that 1957
was a very early use of the term "bit." This is in fact quite
interesting: Many people today do not realize that transmission of
binary information over electrical circuits has been going on for a good
170 years or so, but the term "bit" was not commonly used until about
fifty years ago.
The 1953 edition on "Principles of Electricity applied to Telephone and
Telegraph Work" [aka the AT&T Big Green Book] does not use the word
"bit" anywhere in its 350+ pages, except to refer to "bits of paper" and
"bits of iron." However, they use the following terms extensively:
Make or Break
Mark and Space
Dot and Dash
I will leave it to others to expand this thread further. When I get
started about technology and semantics there is significant risk of a
5,000 word diatribe flowing from my keyboard...
Jim
**************************************************
Speaking from a secure undisclosed location.
Date: Thu, 12 May 2011 05:08:54 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Donner Summit fiber optic cable routes?
Message-ID: <iqfq16$e6l$2@reader1.panix.com>
AES <siegman@stanford.edu> writes:
>Reason for asking: Over the past several centuries Donner Pass has been
>a major route across the Sierras and into California for many modes of
>communication and transit, including:
Ditto Relay, Maryland.
http://www.npr.org/templates/story/story.php?storyId=1030846
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
Date: Thu, 12 May 2011 09:26:23 -0700 (PDT)
From: Lisa or Jeff <hancock4@bbs.cpcn.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: History--T1 line engineering
Message-ID: <4d35c3bc-a779-4eb4-9905-d4481610b51f@c26g2000vbq.googlegroups.com>
For those interested in the technical details of digital transmission
the following may be of interest.
The T1 digital line was a major component of transmission of the Bell
System. It used 24 voice channels, PCM, with a line signal of
1,544,000 bipolar pulse positions per second.
The March 1963 BSTJ has a technical article describing the engineering
of the T1 for repeaters, which were placed roughly every 6,000 feet.
Amplifying signals on a digital line was a different approach than for
the older analog lines. This article considers design limits from
crosstalk from other T1 lines and noise from the central office, as
well as error rates, signal loss, and signal-to-noise ratio.
http://www.alcatel-lucent.com/bstj/vol42-1963/articles/bstj42-2-431.pdf
more on T1 (also known as DS1)
http://en.wikipedia.org/wiki/Digital_Signal_1
Date: Thu, 12 May 2011 12:39:02 -0400 (EDT)
From: Lisa or Jeff <lisa_or_jeff@invalid.telecom-digest.org>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: BSTJ Telstar
Message-ID: <8CDDEDA3BCB1BEC-2478-27211@webmail-m142.sysops.aol.com>
Knowing of your interest in radio, you might find the following
interesting. It's amazing the basic issues that we take for granted
today all had to be carefully worked out.
The July 1963 issue of the Bell Labs Technical Journal contains
multiple articles on the pioneer satellite. They explain the
background of the satellite and ground systems used and the results to
date of publication. Things such as power, bandwidth, antenna gain,
radio path loss, stability, beam focus, Van Allen belts, and orbit
parameters are covered in technical detial.
http://www.alcatel-lucent.com/bstj/vol42-1963/bstj-vol42-issue04.html
J.
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