Getting matching transformer from telephone

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
"Floyd L. Davidson" wrote:

Ross Herbert <rherber1@bigpond.net.au> wrote:
floyd@apaflo.com (Floyd L. Davidson) wrote:
:Ross Herbert <rherber1@bigpond.net.au> wrote:
:
:> voice frequency circuits were all 300 - 3400Hz in my day.
:
:The PSTN is specified from 400 to 2800 Hz, with 24 dB SNR.
:
:Individual channels on various carrier systems, and some
:private line voice circuits are specified with more
:bandwidth.

In Australia PSTN is specified for 300 - 3400 Hz bandwidth.

I doubt it.

You're just plain wrong about everything.
Click to expand...
Which would be easy to prove if it were true, but you
can't. Therefore it seems I am certainly quite correct!

"Most of the current telephone systems are still restricted to the historically
motivated limitation of the bandwidth from 0.3 to 3.4 kHz."
http://portal.acm.org/citation.cfm?id=1142855&dl=&coll=
Click to expand...
Do you have any idea what they are talking about?
(Indeed, do they?) They mention the *maximum* bandwidth
for a single PCM carrier channel, and of course if you
link multiple channels together, and put a 5 mile cable
pair on either end... you *can't* get that bandwidth.

Which is exactly why the PSTN has a minimum bandwidth
specification of 400-2800 Hz.

http://advancingphysics.iop.org/previous/wb/teacher/BandwidthW6.pdf
Click to expand...
That says exactly *nothing* about bandwidth
specifications for the PSTN. Did you even read it?

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
 
On Sun, 04 Jan 2009 11:35:39 -0500, Michael A. Terrell wrote:

PCPaul wrote:

On Sat, 03 Jan 2009 11:03:29 -0500, Michael A. Terrell wrote:

Gun control is for morons and cowards. England is the perfect
example
of a nation governed by cowards who are afraid of armed citizens.

Afraid of armed Yanks, definitely.

24% of the US casualties in the first Gulf War were down to 'friendly
fire'.

24%.


'Friendly fire' accidents do happen. Mostly due to the troops of
various countries not following the instructions for proper ID, correct
passwords, or keeping up with the proper communications for the day or
mission. Some are simply where they were told not to be. Either they
ignored the orders, or the command chain was so slow it never arrived.
Click to expand...
They do. But they happen far more in some countries armies than others.


Would you rather they be captured and tortured to death by the enemy?
Click to expand...
As opposed to being wounded or killed by their 'friends'? No.
 
On Tue, 06 Jan 2009 21:27:09 +0000, PCPaul wrote:

On Sun, 04 Jan 2009 11:35:39 -0500, Michael A. Terrell wrote:

PCPaul wrote:

On Sat, 03 Jan 2009 11:03:29 -0500, Michael A. Terrell wrote:

Gun control is for morons and cowards. England is the perfect
example
of a nation governed by cowards who are afraid of armed citizens.

Afraid of armed Yanks, definitely.

24% of the US casualties in the first Gulf War were down to 'friendly
fire'.

24%.


'Friendly fire' accidents do happen. Mostly due to the troops of
various countries not following the instructions for proper ID, correct
passwords, or keeping up with the proper communications for the day or
mission. Some are simply where they were told not to be. Either they
ignored the orders, or the command chain was so slow it never arrived.

They do. But they happen far more in some countries armies than others.


Would you rather they be captured and tortured to death by the
enemy?

As opposed to being wounded or killed by their 'friends'? No.
Click to expand...
Or rather yes. Damn.


I guess I'll have to stop Yank baiting now.

However - having worked for the MOD as a civvie for many years, I know
loads of UK service personnel. And they are unanimously nervous of being
posted to places where they have to fight alongside US forces. That ain't
right.
 
PCPaul wrote:
On Sun, 04 Jan 2009 11:35:39 -0500, Michael A. Terrell wrote:

PCPaul wrote:

On Sat, 03 Jan 2009 11:03:29 -0500, Michael A. Terrell wrote:

Gun control is for morons and cowards. England is the perfect
example
of a nation governed by cowards who are afraid of armed citizens.

Afraid of armed Yanks, definitely.

24% of the US casualties in the first Gulf War were down to 'friendly
fire'.

24%.


'Friendly fire' accidents do happen. Mostly due to the troops of
various countries not following the instructions for proper ID, correct
passwords, or keeping up with the proper communications for the day or
mission. Some are simply where they were told not to be. Either they
ignored the orders, or the command chain was so slow it never arrived.

They do. But they happen far more in some countries armies than others.

Would you rather they be captured and tortured to death by the enemy?

As opposed to being wounded or killed by their 'friends'? No.
Click to expand...

Have you ever been in combat, or even in the military?


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There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.
 
PCPaul wrote:
On Tue, 06 Jan 2009 21:27:09 +0000, PCPaul wrote:

On Sun, 04 Jan 2009 11:35:39 -0500, Michael A. Terrell wrote:

PCPaul wrote:

On Sat, 03 Jan 2009 11:03:29 -0500, Michael A. Terrell wrote:

Gun control is for morons and cowards. England is the perfect
example
of a nation governed by cowards who are afraid of armed citizens.

Afraid of armed Yanks, definitely.

24% of the US casualties in the first Gulf War were down to 'friendly
fire'.

24%.


'Friendly fire' accidents do happen. Mostly due to the troops of
various countries not following the instructions for proper ID, correct
passwords, or keeping up with the proper communications for the day or
mission. Some are simply where they were told not to be. Either they
ignored the orders, or the command chain was so slow it never arrived.

They do. But they happen far more in some countries armies than others.


Would you rather they be captured and tortured to death by the
enemy?

As opposed to being wounded or killed by their 'friends'? No.

Or rather yes. Damn.

I guess I'll have to stop Yank baiting now.

However - having worked for the MOD as a civvie for many years, I know
loads of UK service personnel. And they are unanimously nervous of being
posted to places where they have to fight alongside US forces. That ain't
right.
Click to expand...

Then they should be better trained to work with other troops.



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There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.
 
On Tue, 06 Jan 2009 17:06:52 -0500, Michael A. Terrell wrote:

PCPaul wrote:

On Tue, 06 Jan 2009 21:27:09 +0000, PCPaul wrote:

On Sun, 04 Jan 2009 11:35:39 -0500, Michael A. Terrell wrote:

PCPaul wrote:

On Sat, 03 Jan 2009 11:03:29 -0500, Michael A. Terrell wrote:

Gun control is for morons and cowards. England is the perfect
example
of a nation governed by cowards who are afraid of armed citizens.

Afraid of armed Yanks, definitely.

24% of the US casualties in the first Gulf War were down to
'friendly fire'.

24%.


'Friendly fire' accidents do happen. Mostly due to the troops of
various countries not following the instructions for proper ID,
correct passwords, or keeping up with the proper communications for
the day or mission. Some are simply where they were told not to be.
Either they ignored the orders, or the command chain was so slow it
never arrived.

They do. But they happen far more in some countries armies than
others.


Would you rather they be captured and tortured to death by the
enemy?

As opposed to being wounded or killed by their 'friends'? No.

Or rather yes. Damn.

I guess I'll have to stop Yank baiting now.

However - having worked for the MOD as a civvie for many years, I know
loads of UK service personnel. And they are unanimously nervous of
being posted to places where they have to fight alongside US forces.
That ain't right.


Then they should be better trained to work with other troops.
Click to expand...
Training to hide from them, you mean?

'Working with other troops' doesn't mean 'shoot first, ask questions
later'. Maybe it's a language thing.

I *know* that US simulator training has had to have massive amounts of
work done in the last few years to add 'friendlies' into the equation.
even then there was a lot of resistance to having hitting one of these
friendlies actually damage the health or 'score' of the shooter.. it
spoiled the fun of blasting everything that moved.

Anyway, if the combined non-US coalition forces couldn't get through to
the US hierarchy, then me moaning at you on here isn't going to do
anything, so I'm off now. Bye.
 
PCPaul wrote:
On Tue, 06 Jan 2009 17:06:52 -0500, Michael A. Terrell wrote:

PCPaul wrote:

On Tue, 06 Jan 2009 21:27:09 +0000, PCPaul wrote:

On Sun, 04 Jan 2009 11:35:39 -0500, Michael A. Terrell wrote:

PCPaul wrote:

On Sat, 03 Jan 2009 11:03:29 -0500, Michael A. Terrell wrote:

Gun control is for morons and cowards. England is the perfect
example
of a nation governed by cowards who are afraid of armed citizens.

Afraid of armed Yanks, definitely.

24% of the US casualties in the first Gulf War were down to
'friendly fire'.

24%.


'Friendly fire' accidents do happen. Mostly due to the troops of
various countries not following the instructions for proper ID,
correct passwords, or keeping up with the proper communications for
the day or mission. Some are simply where they were told not to be.
Either they ignored the orders, or the command chain was so slow it
never arrived.

They do. But they happen far more in some countries armies than
others.


Would you rather they be captured and tortured to death by the
enemy?

As opposed to being wounded or killed by their 'friends'? No.

Or rather yes. Damn.

I guess I'll have to stop Yank baiting now.

However - having worked for the MOD as a civvie for many years, I know
loads of UK service personnel. And they are unanimously nervous of
being posted to places where they have to fight alongside US forces.
That ain't right.


Then they should be better trained to work with other troops.

Training to hide from them, you mean?
Click to expand...

Not surprising that they want to hide. Hiding in the wrong place gets
you killed.


'Working with other troops' doesn't mean 'shoot first, ask questions
later'. Maybe it's a language thing.
Click to expand...

The inability to follow orders. Whoever has the largest number of
troops in an area has to set the rules. the others either work with
them, get enough additional troops of their own, or admit they are
useless and go home.



I *know* that US simulator training has had to have massive amounts of
work done in the last few years to add 'friendlies' into the equation.
even then there was a lot of resistance to having hitting one of these
friendlies actually damage the health or 'score' of the shooter.. it
spoiled the fun of blasting everything that moved.
Click to expand...

Simulators don't return live fire.


Anyway, if the combined non-US coalition forces couldn't get through to
the US hierarchy, then me moaning at you on here isn't going to do
anything, so I'm off now. Bye.
Click to expand...

Admitting that you're off is the first stage of healing. ;-)



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There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.
 
In article <4963B300.C2EC6BAC@hotmail.com>, Eeyore <rabbitsfriendsandrel
ations@hotmail.com> scribeth thus
John Livingston wrote:

Floyd L. Davidson wrote:

You mean ITU-T standards, which is what both the UK and
Australia use. (It hasn't been CCITT for a long time.)

You are citing the bandwidth for an individual *channel*.
It is not possible to provide that sort of bandwidth on
every local loop, and therefore significantly less is
required for a complete connection or for any individual
loop.

Are we discussing the same thing, I wonder ? The "Local Loop" is the
exchange - subscriber path, and is not bandwidth limited other than by
the basic line parameters. Hence the reason a local loop can (typically)
support 8Mbit ADSL.

Or up to 24 Mbps ADSL2+ !

Graham
Click to expand...
When you live -in- an exchange that is;!...
--
Tony Sayer
 
On Tue, 06 Jan 2009 04:53:17 -0900, floyd@apaflo.com (Floyd L. Davidson) wrote:

:Ross Herbert <rherber1@bigpond.net.au> wrote:
:>On Sun, 04 Jan 2009 20:36:09 -0900, floyd@apaflo.com (Floyd L. Davidson)
wrote:
:>
:>:Ross Herbert <rherber1@bigpond.net.au> wrote:
:>:
:>:> voice frequency circuits were all 300 - 3400Hz in my day.
:>:
:>:The PSTN is specified from 400 to 2800 Hz, with 24 dB SNR.
:>:
:>:Individual channels on various carrier systems, and some
:>:private line voice circuits are specified with more
:>:bandwidth.
:>:
:>
:>In Australia PSTN is specified for 300 - 3400 Hz bandwidth.
:
:I doubt it.


Well let's give some examples...

When I was involved in junction commissioning (unloaded copper inter-exchange VF
junctions) with Telstra, transmission measurements were carried out over the
300-3400Hz range. This hasn't altered.

When looking at the transmission characteristics of an international telephone
exchange (ITU-T Recommendations)the only frequency range mentioned is
300-3400Hz.
http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-Q.45-198410-I!!PDF-E&type=items
http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-Q.45bis-198811-I!!PDF-E&type=items

And the following document recommends all channel terminal equipment be lined up
using 300-3400Hz.
http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.120-199812-I!!PDF-E&type=items

Note that ITU-T G235 (3KHz spacing) is supesrseded and is no longer recommended
for international connections.

As for the specification relating to customer equipment connected to the PSTN
the frequency range used for testing is 100Hz - 4KHz.
http://www.commsalliance.com.au/documents/standards/S004:2008

In other documents from this website the definition of VF telephony or Voiceband
is 300-3400Hz.

There probably a number of other publications if I had the time to research them
but suffice to say that in Australia the VF telephony channel bandwidth is
specified as per ITU recommendations ie. 300-3400Hz.
 
Ross Herbert wrote:
On Tue, 06 Jan 2009 04:53:17 -0900, floyd@apaflo.com (Floyd L. Davidson) wrote:

:Ross Herbert <rherber1@bigpond.net.au> wrote:
:>On Sun, 04 Jan 2009 20:36:09 -0900, floyd@apaflo.com (Floyd L. Davidson)
wrote:
:
:>:Ross Herbert <rherber1@bigpond.net.au> wrote:
:>:
:>:> voice frequency circuits were all 300 - 3400Hz in my day.
:>:
:>:The PSTN is specified from 400 to 2800 Hz, with 24 dB SNR.
:>:
:>:Individual channels on various carrier systems, and some
:>:private line voice circuits are specified with more
:>:bandwidth.
:>:
:
:>In Australia PSTN is specified for 300 - 3400 Hz bandwidth.
:
:I doubt it.


Well let's give some examples...

When I was involved in junction commissioning (unloaded copper inter-exchange VF
junctions) with Telstra, transmission measurements were carried out over the
300-3400Hz range. This hasn't altered.

When looking at the transmission characteristics of an international telephone
exchange (ITU-T Recommendations)the only frequency range mentioned is
300-3400Hz.
http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-Q.45-198410-I!!PDF-E&type=items
http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-Q.45bis-198811-I!!PDF-E&type=items

And the following document recommends all channel terminal equipment be lined up
using 300-3400Hz.
http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.120-199812-I!!PDF-E&type=items

Note that ITU-T G235 (3KHz spacing) is supesrseded and is no longer recommended
for international connections.

As for the specification relating to customer equipment connected to the PSTN
the frequency range used for testing is 100Hz - 4KHz.
http://www.commsalliance.com.au/documents/standards/S004:2008

In other documents from this website the definition of VF telephony or Voiceband
is 300-3400Hz.

There probably a number of other publications if I had the time to research them
but suffice to say that in Australia the VF telephony channel bandwidth is
specified as per ITU recommendations ie. 300-3400Hz.
Click to expand...
Good, accurate stuff, Ross.

I really don't know where Floyd L. Davidson is coming from. He is grimly
sticking to an assertion the the UK and Australian PSTN is specified as
"400 to 2800 KHz", but has been unable to quote his source in terms of
unambiguous specifications.

I can only assume - from his location - that he has some experience as a
technician in military comms systems, and has some view of the US Bell
system. Hence the belief in "400-2800". As has been fully demonstrated
by several others, this is a profound misunderstanding of the
international PSTN.

This thread has wandered far and wide from the OP's question, but it's
getting a bit too far off the subject for me. It's also degenerated into
a classic battle of the Trolls.

If Floyd wishes to make further wild and inaccurate statements, perhaps
he would like to open a new thread ?

John
 
John Livingston <null@spambin.com> wrote:
Good, accurate stuff, Ross.
Click to expand...
All of it referenced the specifications for individual
channels on various facilities. None of it had to do
with the overall minimum allowed specification for an
end to end connection via the PSTN.

I really don't know where Floyd L. Davidson is coming from.
Click to expand...
More than three decades in the long distance
telecommuncations industry (but not with the Bell
System).

I can only assume - from his location - that he has some experience as a
technician in military comms systems, and has some view of the US Bell
system. Hence the belief in "400-2800". As has been fully demonstrated
by several others, this is a profound misunderstanding of the
international PSTN.
Click to expand...
I do understand that you cannot specify each channel end
to end at one bandwidth, and then switch them and
connect cable plant to the worst case customer and have
the same bandwidth! That is what you are claiming, and
any simple reality check should be enough to indicate
the problem.

This thread has wandered far and wide from the OP's question, but it's
getting a bit too far off the subject for me. It's also degenerated into
a classic battle of the Trolls.
Click to expand...
Threads drift. Whooo Hooo.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com
 
On Wed, 07 Jan 2009 06:52:48 -0900, floyd@apaflo.com (Floyd L. Davidson) wrote:

:John Livingston <null@spambin.com> wrote:
:>
:>Good, accurate stuff, Ross.
:
:All of it referenced the specifications for individual
:channels on various facilities. None of it had to do
:with the overall minimum allowed specification for an
:end to end connection via the PSTN.

Hold it, that's a dumb statement.

The ITU recommendation for international VF channel bandwidth is 300-3400Hz, so
why would it be necessary to "allow a minimum" bandwidth of 400-2800Hz? If the
300-3400Hz applies to ALL channels used in an end-to-end international link,
then it follows that the overall bandwidth is 300-3400Hz.

Obviously the ITU spec is greater than the so-called "minimum" of 400-2800Hz, so
it is not necessary to "allow a minimum" bandwidth of less than this.

The fact that some administrations may not have adopted the ITU recommendation
and continue to use 400-2800Hz simply means that they are not prepared to
upgrade their equipment and are therefore behind the times. Any communication
carried over such links will mean the overall bandwidth is degraded even if some
sections do conform to the ITU recommendation of 300-3400Hz.

:
:>I really don't know where Floyd L. Davidson is coming from.
:
:More than three decades in the long distance
:telecommuncations industry (but not with the Bell
:System).

And I have 37 years of Telco experience from 56 - 93 in both metro and long-line
installations. In all those years we used 300-3400Hz.
 
On Tue, 06 Jan 2009 19:47:17 +0000, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

:
:
:Ross Herbert wrote:

:> With regard to a POTS line the VF bandwidth is some 300 - 3400Hz - hardly
hi-fi
:> - so optimal flat frequency response is not an issue.
:>
:> The fact that the secondary impedance of the 600 ohm transformer does not
match
:> the input impedance of the sound card is totally unimportant in this
:> application.
:
:So your attitude is "it's so bad it doesn't matter messing it up even more".

Not at all. Any practical measurement of the degradation of a 300-3400Hz signal
using the 600 ohm transformer would be insignificant. If your assumption that
audio degradation when using a 600:600 transformer was valid then why is there
no available audio transformer, with a 3.5Kv isolation rating, to match a 600
ohm telephone line to a high impedance (eg. 10K ohm) input? The answer has to
be, "it's not necessary".

:
:A proper 600:600 transformer will be more expensive than a 10k:10k one too.
:

That may be true but how many readily available 10K:10K audio transformers have
a 3.5Kv isolation rating?

In order to conform to the required isolation rating of 3.5Kv between the mains
powered PC and the telephone line, the only transformer which is readily
available, and complies, is an approved 600:600 transformer.
 
In article <foiam451b5qv851h5ko7702391hgu63732@4ax.com>, Ross Herbert
<rherber1@bigpond.net.au> scribeth thus
On Wed, 07 Jan 2009 06:52:48 -0900, floyd@apaflo.com (Floyd L. Davidson) wrote:

:John Livingston <null@spambin.com> wrote:
:
:>Good, accurate stuff, Ross.
:
:All of it referenced the specifications for individual
:channels on various facilities. None of it had to do
:with the overall minimum allowed specification for an
:end to end connection via the PSTN.

Hold it, that's a dumb statement.

The ITU recommendation for international VF channel bandwidth is 300-3400Hz, so
why would it be necessary to "allow a minimum" bandwidth of 400-2800Hz? If the
300-3400Hz applies to ALL channels used in an end-to-end international link,
then it follows that the overall bandwidth is 300-3400Hz.
Click to expand...
Ummmm... those figures are not -quite- that meaningful unless we have
some sort of reference level ..

i.e. 300 to 3400 +/- ? dB ...


Obviously the ITU spec is greater than the so-called "minimum" of 400-2800Hz, so
it is not necessary to "allow a minimum" bandwidth of less than this.

The fact that some administrations may not have adopted the ITU recommendation
and continue to use 400-2800Hz simply means that they are not prepared to
upgrade their equipment and are therefore behind the times. Any communication
carried over such links will mean the overall bandwidth is degraded even if some
sections do conform to the ITU recommendation of 300-3400Hz.

:
:>I really don't know where Floyd L. Davidson is coming from.
:
:More than three decades in the long distance
:telecommuncations industry (but not with the Bell
:System).

And I have 37 years of Telco experience from 56 - 93 in both metro and long-line
installations. In all those years we used 300-3400Hz.
Click to expand...
--
Tony Sayer
 
"tony sayer" <tony@bancom.co.uk> wrote in message
news:Z0n1zqQBseZJFw3z@bancom.co.uk...
In article <foiam451b5qv851h5ko7702391hgu63732@4ax.com>,
Ross Herbert
rherber1@bigpond.net.au> scribeth thus
On Wed, 07 Jan 2009 06:52:48 -0900, floyd@apaflo.com (Floyd
L. Davidson) wrote:

:John Livingston <null@spambin.com> wrote:
:
:>Good, accurate stuff, Ross.
:
:All of it referenced the specifications for individual
:channels on various facilities. None of it had to do
:with the overall minimum allowed specification for an
:end to end connection via the PSTN.

Hold it, that's a dumb statement.

The ITU recommendation for international VF channel
bandwidth is 300-3400Hz, so
why would it be necessary to "allow a minimum" bandwidth of
400-2800Hz? If the
300-3400Hz applies to ALL channels used in an end-to-end
international link,
then it follows that the overall bandwidth is 300-3400Hz.

Ummmm... those figures are not -quite- that meaningful
unless we have
some sort of reference level ..

i.e. 300 to 3400 +/- ? dB ...



Obviously the ITU spec is greater than the so-called
"minimum" of 400-2800Hz, so
it is not necessary to "allow a minimum" bandwidth of less
than this.

The fact that some administrations may not have adopted the
ITU recommendation
and continue to use 400-2800Hz simply means that they are
not prepared to
upgrade their equipment and are therefore behind the times.
Any communication
carried over such links will mean the overall bandwidth is
degraded even if some
sections do conform to the ITU recommendation of 300-3400Hz.

:
:>I really don't know where Floyd L. Davidson is coming
from.
:
:More than three decades in the long distance
:telecommuncations industry (but not with the Bell
:System).

And I have 37 years of Telco experience from 56 - 93 in both
metro and long-line
installations. In all those years we used 300-3400Hz.


--
Tony Sayer
Click to expand...
What do you suppose happens to the bandwidth of a signal as it
is passed through successive audio devices that are band
limited to 300-3400 Hz?

Would you expect to get 300-3400Hz +- ndB response in an end
to end loopback test when you use white noise as the test
signal? (n =ITU spec)

Going from a handset to a PBX to MUX to a CO into the network
and back if each device has a 300-3400Hz response the looped
back signal should be more band limited than the first device
in the signal chain with 300-3400Hz response originating test
signal by quite some bit.


Peace
dawg
 
On Thu, 8 Jan 2009 16:18:52 -0500, "Wecan do it" <WeCanDoit@nospam.com> wrote:

:
:What do you suppose happens to the bandwidth of a signal as it
:is passed through successive audio devices that are band
:limited to 300-3400 Hz?
:
:Would you expect to get 300-3400Hz +- ndB response in an end
:to end loopback test when you use white noise as the test
:signal? (n =ITU spec)
:
:Going from a handset to a PBX to MUX to a CO into the network
:and back if each device has a 300-3400Hz response the looped
:back signal should be more band limited than the first device
:in the signal chain with 300-3400Hz response originating test
:signal by quite some bit.
:

I suggest you do some research on the various ITU documents, eg.
http://www.itu.int/rec/T-REC-P/e
http://www.itu.int/rec/T-REC-O/e

or pick any relevant section from the main page
http://www.itu.int/ITU-T/publications/recs.html
 
In article <ou5dm4plk5j62kgll8vm7qnhggbtdmd1u7@4ax.com>,
Ross Herbert <rherber1@bigpond.net.au> wrote:

On Thu, 8 Jan 2009 16:18:52 -0500, "Wecan do it" <WeCanDoit@nospam.com> wrote:

:
:What do you suppose happens to the bandwidth of a signal as it
:is passed through successive audio devices that are band
:limited to 300-3400 Hz?
:
:Would you expect to get 300-3400Hz +- ndB response in an end
:to end loopback test when you use white noise as the test
:signal? (n =ITU spec)
:
:Going from a handset to a PBX to MUX to a CO into the network
:and back if each device has a 300-3400Hz response the looped
:back signal should be more band limited than the first device
:in the signal chain with 300-3400Hz response originating test
:signal by quite some bit.
:

I suggest you do some research on the various ITU documents, eg.
http://www.itu.int/rec/T-REC-P/e
http://www.itu.int/rec/T-REC-O/e

or pick any relevant section from the main page
http://www.itu.int/ITU-T/publications/recs.html
Click to expand...
If you know anything about circuit theory, you understand that a
filter's frequency behavior is determined by poles in the complex s
plane where s - -a + jw and a is positive to keep stability. Whatever
the poles are for a single filter section, lining them up in tandem will
have multiple poles. The effect for your basic two-pole bandpass filter
is to sharpen the skirts and reduce your 3 dB bandwidth,

Bill

--
Private Profit; Public Poop! Avoid collateral windfall!
 
"Floyd L. Davidson" wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
"Floyd L. Davidson" wrote:

The PSTN is specified from 400 to 2800 Hz, with 24 dB SNR.

By WHOM ?

ITU-T standards and Bellcore standards.
Click to expand...
Bell don't count as they're not International.

Since everyone else says ITU-T say 300-3400Hz I suspect we're seeing
another case of you being stuck in a time warp.

Graham
 
Ross Herbert wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
:
:A proper 600:600 transformer will be more expensive than a 10k:10k one too.
:
That may be true but how many readily available 10K:10K audio transformers have
a 3.5Kv isolation rating?
Click to expand...
I believe this was required IIRC for only brief use. He could avoid using it during
thunderstorms too.
http://uk.farnell.com/triad-magnetics/ty-141p/transformer-audio-0-1w/dp/1610409
Probably in stock at Newark

Graham
 
Eeyore wrote:

Ross Herbert wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
:
:A proper 600:600 transformer will be more expensive than a 10k:10k one too.
:
That may be true but how many readily available 10K:10K audio transformers have
a 3.5Kv isolation rating?

I believe this was required IIRC for only brief use. He could avoid using it during
thunderstorms too.
http://uk.farnell.com/triad-magnetics/ty-141p/transformer-audio-0-1w/dp/1610409
Probably in stock at Newark
Click to expand...
http://www.farnell.com/datasheets/120167.pdf

Data sheet implies may be suitable for telephone coupling.

Graham
 
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