29 Years of the Digest ... founded August 21, 1981
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The Telecom Digest for May 12, 2011
Volume 30 : Issue 119 : "text" Format
====== 29 years of TELECOM Digest -- Founded August 21, 1981 ====== |
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Date: Tue, 10 May 2011 19:47:46 -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: <E_ydndNE-PZOd1TQnZ2dnUVZ_oGdnZ2d@earthlink.com>
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". Things like characters, words, bytes, packets,
frames, etc are formed at higher levels of the 7 layer OSI stack by
the DTE equipment attached to the data circuit.
see http://en.wikipedia.org/wiki/Osi_stack
--Reed
Date: Wed, 11 May 2011 17:51:27 -0500
From: bonomi@host122.r-bonomi.com (Robert Bonomi)
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: History Early Data transmission technical considerations
Message-ID: <G-SdnbbmN-Nyj1bQnZ2dnUVZ_rOdnZ2d@posted.nuvoxcommunications>
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.
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