LinuxSA Mailing list archives

  From: Richard Walford <rwalford@picknowl.com.au>
  To  : Daryl Tester <dt@picknowl.com.au>
  Date: Sun, 26 Nov 2000 11:52:58 +1030

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

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.
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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