LinuxSA Mailing list archives

  From: Richard Sharpe <sharpe@ns.aus.com>
  To  : Richard Walford <rwalford@picknowl.com.au>
        Daryl Tester <dt@picknowl.com.au>
  Date: Sat, 25 Nov 2000 20:18:54 +1000

Re: ADSL Enabled Exchange Areas: Updated 20/11/2000

At 11:52 AM 11/26/00 +1030, Richard Walford wrote:
>I found the Telstra reference at
>http://www.telstra.com.au/sfoa/docs/psts.doc , under ATTACHMENT 1:SERVICE
>PERFORMANCE SPECIFICATIONS.
>
>CONDITIONS NOT SUPPORTED
>The following terminal operating conditions are not supported by Telstra and
>may affect the PSTS service levels in this Attachment:
>....
>Data modems and facsimile Customer Equipment working at data signalling
>rates greater than 2400 bit/s.

This indicates confusion, and was probably not checked by one of Telstra's
techos. 'signalling rates' indicates baud, while they have written 2400
b/s, which as others have said, is not the same. 

>Data modems and facsimile Customer Equipment not conforming to ITU-T
>Recommendations V.18, V.21, V.27 ter or V.34.
>...
>
>So it was my memory playing tricks, Telstra do not state baud but they do
>state a signalling rate no greater than 2400 bps. Doh...
>
>Anyway, enough of the trivia, the only real limiting factor in Telstra's
>network these days is the local loop.  From the originating exchange card to
>the terminating exchange card Telstra carry all voice calls over a 64K
>digital channel.  Thus, there is no reason (other than marketing/product
>management and the grab for cash) that Telstra could not offer a base rate
>ISDN service as it's base level PSTN offering.  In doing so the need for V90
>modem technology would basically disappear along with all the quirks and
>problems that modem technology brings with it.
>
>Regards,
>
>Richard
>
>----- Original Message -----
>From: "Daryl Tester" <dt@picknowl.com.au>
>To: "Richard Walford" <rwalford@picknowl.com.au>
>Cc: <linuxsa@linuxsa.org.au>
>Sent: Saturday, 25 November 2000 9:18 PM
>Subject: Re: ADSL Enabled Exchange Areas: Updated 20/11/2000
>
>
>> Richard Walford wrote:
>>
>> > Sorry, the latest documentation from Telstra available on their web
>sites
>> > (now If I could rember where, umm maybe USO pages) explicitly states
>2400
>> > bps.
>>
>> The USO that I downloaded makes no mention of this.  And if Telstra
>> have stated this, then that means that they've got it wrong, and that
>> they are now unable to distinguish the difference between baud and
>> BPS.  Baud is not the same as BPS (technically untrue, as most
>> signalling that occurs below 2400 bps the two are the equivalent rate).
>>
>> > In fact I don't believe the USO (Universal Service Offering) actually
>> > defines what speed Telstra has to supply - I think you will find that
>> > Telstra only has to supply a voice grade service.
>>
>> Which is where the 2400 baud comes in - it's pretty much the maximum
>> bandwidth that you can squeeze out of a voice grade (3.3 Khz from
>> memory, but I may be out by a few hundred Hertz here) due to Nyquist.
>> Any bitrate over 2400 bps is done "by signalling trickery", like
>> QAM and run length encoding/compression, but the _baud rate_ cannot
>> exceed half the available bandwidth without sampling errors being
>> introduced.  Yet people keep making the same mistake (on both sides
>> of the fence) over and over again.
>>
>> > Feel free to correct me, but please supply a reference to a document
>that
>> > supports your position.
>>
>> Elementary communications, and my dealings with Telecom/Telstra and
>> modems in the mid 80's.
>>
>> BTW, an Altavista site-limited search cannot find any relevant
>> matches for "2400" on either www.telstra.com or www.bigpond.com.
>> I'm keen to see where Telstra have this in print.
>>
>>
>> --
>> Regards,
>>   Daryl Tester,  Software Wrangler and Bit Herder, IOCANE Pty. Ltd.
>>
>> "Who knows what men lurk in the heart of eval?"
>
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>

Regards
-------
Richard Sharpe, sharpe@ns.aus.com
Samba (Team member, www.samba.org), Ethereal (Team member, www.zing.org)
Contributing author, SAMS Teach Yourself Samba in 24 Hours
Author, Special Edition, Using Samba


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