Getting matching transformer from telephone

[tony sayer]

In article <495EF5C0.E2464EA4@hotmail.com>, Eeyore <rabbitsfriendsandrel
ations@hotmail.com> scribeth thus

Stuart wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
High-fidelity Microphone

" Common uses include matching the relatively low 2K ohm output
impedance of a microphone to an amplifier’s much higher line input
impedance of 10K ohms. Studios commonly use the three terminal “XLR”
type of connector which is a balanced connection method with a terminal
for a center tap. A separate ground terminal, tied to the XLR
connector’s case is almost always present. The center tap may be used to
phantom-feed a small amount of current for powering a pre-amp or active
“condenser” microphone."

LMAO !

You mean you didn't know that either?

Ok, a typical dynamic microphone is often nearer 150-300 ohms output

Rather different to 2k I think you'll agree.


impedence and Ribbons can be as low as 50 Ohm but otherwise......

Ribbons are FAR lower. Maybe 50 ohms AFTER the transformer !

And Pin 1 on an XLR is ALWAYS the cable shield. It may also be GROUND -
but
that's another story. It certainly isn't used to provide phantom power
under
ANY circumstances.#

Apart from providing the -return path- for the current sent over the
balanced pair...

And the last time I came across a centre tapped transformer

in pro-audio was 35 years ago. It caused a bloody nuisance too. Modern
balanced audio circuits are 'floating'. The centre tap provides ZERO
advantage.

I now expect you to make an idiot of yourself trying to refute that one.

Graham

--
Tony Sayer

 

[tony sayer]

In article <Xns9B8756CEC79974C1H4@69.16.176.253>, Paul B
<mail@nomail.invalid> scribeth thus

On Wed 31 Dec 22:00, tony sayer <tony@bancom.co.uk> wrote
In article <495BE9F9.6DEA2000@hotmail.com>, Eeyore
rabbitsfriendsandrel ations@hotmail.com> scribeth thus

tony sayer wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> scribeth thus
Archimedes' Lever wrote:

Hey! Floyd doesn't have an attitude, and is pretty darned
good at accepting other standards and practices, once they
are brought to his attention. I am sure he will concur
with you once he realizes from your post, that the
geography and era were different than that he had his
mindset in.

Unfortunately has has NO CLUE about the characteristic
impedance of twisted pair cable as used for telecoms.

http://en.wikipedia.org/wiki/Twisted_pair#
Unshielded_twisted_pair_.28UTP.29

"UTP is also finding increasing use in video applications,
primarily in security cameras. Many middle to high-end
cameras include a UTP output with setscrew terminals. This is
Here's the original.

" I am looking for some 1-to-1 matching transformers to connect
varioua audio devices to my PC. I usually get noises and hum.

These line matching transformers are not so cheap at about Ł6 or
7 each.

Hello Tony and everyone, I am the OP.

I've been away for a few days and I see there's so many posts that
now I'm trying to get through them all!


MY OBJECTIVE

My aim is to take voice recordings made on various equipment and save
them to a PC. Some of the voice recordings are of telephone
conversations made onto tape. I would prefer to have fed the phone
signal direct to the PC but I get a lot of noise.

I want to preserve as much quality as possible because it will
probably be necessary for a third party to identify the person
speaking.

------

Secondly and quite separately from the above....

I didn't raise this problem in my first post. I am getting hum and
noise when I record using a purpose build connector (Retell model 156
~ see link below) to a hand-held battery-powered flash-memory
recorder even when the phone is on hook. I can't see where the hum
is coming from unless it is on the phone line because there can't be
a ground loop this time.

http://www.telephonerecorder.co.uk/recording/connectors/156.htm

I do know my landlines don't have all the hum and noise so they must
be doing something which I want for my recorder! I thought may be a
transformer to better terminate the Virgin Media phone line might
help but I am out of my depth here and line termination may be the
wrong idea altogther.

Interesting that your on VM there shouldn't be any really noticeable
noise with that device from an initial look of it. Any chance of posting
a recording anywhere this might provide an idea of what's up...

DEFINITIONS

I guess my use of the word "matching" is not a very good electrical
description. I'm not seeking to match impedances and I get the
feeling that in electrical engineering, "matching" is often shorthand
for impedence matching. So apologies for any confusion I have
caused.

I want to minimise any ground loop to reduce hum and other spuriae so
perhaps I should have said "isolating" transformer.

Retell have a model (the 157) which connects direct to a PC and I
believe it is identical to the 156 except it has the additional
transformer I am asking about.

That might be wroth a try. On the odd occasion when I've needed to
record a phone call an RS components 1:1 transformer worked very well
'tho I had to pot it down a bit and use a series cap on the input side.
Not exactly strictly tech correct but good enough for purposes..

And that was on a *VM line too....


*Just a note for those not in the UK VM is Virgin Media which is the new
operator for what was/is most of the UK cable companies.

They provide POTS services like BT do but whereas BT will provide
service over up to 7-8 km of copper from an exchange, they tend to use
roadside cabinets, fibre fed using usually Nokia equipment's, with
rarely more than a Kilometre of copper to the subs premises as they only
service urban and sub urban areas..
--
Tony Sayer

 

[Phil Allison]

"Archimedes'= CRIMINAL PSYCHOPATH "


** Report this FUCKING SCUMBAG to his ISP

NOW !!!!!!!!!!!!!!!!


Get the STINKING PIG fucked off usenet for ever.





...... Phil

 

[Phil Allison]

"Archimedes'= CRIMINAL PSYCHOPATH "


** Report this FUCKING SCUMBAG to his ISP

NOW !!!!!!!!!!!!!!!!


Get the STINKING PIG fucked off usenet for ever.





...... Phil

 

[Michael A. Terrell]

Eeyore wrote:

Archimedes' Lever wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
Archimedes' Lever wrote:
"Phil Allison" <philallison@tpg.com.au> wrote:

What the OP *actually asked* was this:

" If I strip down some landline phones I 've got here, then will there
be a matching transformer in each one? "

Which, to anyone with even half a brain, obviously means that he wishes
to utilize it as well, you stupid fucktard!

He can only utilise it if it contains one OBVIOUSLY !

That was not the argument, you retarded non-human dumbfuck.

The word is UTILIZE.

Not in the civilised world.

http://www.thinkscience.co.jp/toolshed/2008/10/british-vs-american-english-spelling/

Graham

Here is the donkey's 'Civilized World'

<http://www.dailymail.co.uk/news/article-1103843/Boozy-Britains-bloody-New-Year-A-999-seven-seconds-alcohol-induced-mayhem.html>


Is it any wonder that they can't spell?


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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.

 

[Michael A. Terrell]

tony sayer wrote:

Eeyore wrote:

And Pin 1 on an XLR is ALWAYS the cable shield. It may also be GROUND -
but
that's another story. It certainly isn't used to provide phantom power
under
ANY circumstances.#

Apart from providing the -return path- for the current sent over the
balanced pair...

Don't confuse him with facts. He has trouble breathing and typing at
the same time.


--
http://improve-usenet.org/index.html

aioe.org, Goggle Groups, and Web TV users must request to be white
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your account: http://www.usenettools.net/ISP.htm


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.

 

[Stuart]

In article <495EEC94.FEAC11DF@hotmail.com>,
Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

It isn't. Not for about 45 years.

45 years ago it certainly was!

--
Stuart Winsor

For Barn dances and folk evenings in the Coventry and Warwickshire area
See: http://www.barndance.org.uk

 

[Eeyore]

"Floyd L. Davidson" wrote:

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

"Pulling the line low"???? Giggle snort,
cough and laugh...

A: OFF HOOK you twit.

Off hook is a loop *current* condition.

WOW. I'd never have guessed !

B: the DC resistance of the transformer primary may cause the phone to stop
working by lowering the line voltage too much.

Typically a split winding is used, with a mid-point
capacitor to block DC current.

What a load of Bollocks !

Transformers are neither needed nor used any more.

Graham

 

[Eeyore]

"Floyd L. Davidson" wrote:

It has worked for roughly 100 years

Is that how long you've been practicing telephony ?

Graham

 

[Eeyore]

"Floyd L. Davidson" wrote:

You have that backwards. If you use a properly designed
pad with the correct impedance it will maximized common
mode rejection of induced currents.

As far as to how using correctly designed pads are
unsafe, I'll pass on that one and let you explain what
you think you are saying. (Because I just can't imagine
how a proper pad, or even an improper one, is unsafe.)

"Howls of derisive laughter" Bruce:

Graham

 

[Eeyore]

"Floyd L. Davidson" wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

Look, I've designed line interfaces FFS. For Xerox. I've already
mentioned it once.

You can say anything you like, but when you make up all
the ridiculous garbage you are posting to this thread
there is little doubt that you haven't got even the
faintest clue how telecommuncations equipment works.

Want to to see the schematics ? I'm sure I still have them here
somewhere.

Graham

 

[Eeyore]

"Floyd L. Davidson" wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
Phil Allison wrote:

plus cap couple the input side to stop pulling the line low.

Damn right ! Not ONE of these 'phone experts' has mentioned that.

BS. I had previously discussed it in detail.

You are full of BS.

 

[Eeyore]

Archimedes' Lever wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

You are DimBulb and I claim my Ł1000.

No, I am your superior, and there is nothing that you can do about it,
amp boy.

Proof positive. How's your DSP btw ? Ultra-low noise analogue circuitry,
interfacing one to the other etc ?

Graham

 

[Eeyore]

Stuart wrote:

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
It isn't. Not for about 45 years.

45 years ago it certainly was!

Minority use even then.

Try and think WHY.

Graham

 

[tony sayer]

In article <495F6025.9C826A31@hotmail.com>, Eeyore <rabbitsfriendsandrel
ations@hotmail.com> scribeth thus

"Floyd L. Davidson" wrote:

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

"Pulling the line low"???? Giggle snort,
cough and laugh...

A: OFF HOOK you twit.

Off hook is a loop *current* condition.

WOW. I'd never have guessed !


B: the DC resistance of the transformer primary may cause the phone to stop
working by lowering the line voltage too much.

Typically a split winding is used, with a mid-point
capacitor to block DC current.

What a load of Bollocks !

Transformers are neither needed nor used any more.

Graham

Umm... beg to differ .. they are used for 2 and 4 wire analogue or
analogue over digital voice band private circuits...

And they do sometimes use DC blocks but rarely now as point to point DC
available paths are rather rare unless on the same ends of the serving
exchange.....
--
Tony Sayer

 

[Phil Allison]

"Stuart" <Spambin@argonet.co.uk>

** Another fucking tenth witted autistic pommy cunt.

And Pin 1 on an XLR is ALWAYS the cable shield.

Did it suggest anything other than that in the given description?

It may also be GROUND - but that's another story.

It is always grounded, directly or indirectly, otherwise the screen fails
to be effective.

** More pedantic, pommy fuckwit nonsense.

Screening works even if there is no connection to AC supply ground or
actual ground.

It certainly isn't used to provide phantom power under ANY circumstances.

So how does phantom power work then?

** Shame a dumb as dog shit pommy cunt like YOU has no fucking clue.

Ain't it - eh ??

And the last time I came across a centre tapped transformer in pro-audio
was 35 years ago.

Why do you think people such as www.Lundahl.se and others are still
manufacturing and selling them, even introducing new designs.

** Go ask them why - fuckhead.

Such fake arguments ( based on a LACK of evidence) have no logical basis.

At a one-off price of around 20-30 quid they must be manufacturing them in
"quantity"

R.S. Components are a hard-headed, very commercially minded
electrical/electronics distributor, who only stock stuff they can shift in
quantity, yet they still list a centre-tapped primary, microphone
transformer

** Such units are sometimes used in * DI boxes* et alia to receive phantom
power - not deliver it.

Most mic trannys have centre taps on the low Z side - nothing more than an
historical relic.

In an article in Electronics World April 1991, Douglas Self of Soundcraft
stated "It is now rare to use input transformers...." It is clear,
therefore, that they were still being used, even if only in specialist
applications. That is a bare 18 years ago.

** Wot fucking asinine reverse logic drivel.

Doug Self is a smug, pompous idiot - at best.

His hands on experience with any area of pro-audio practice or design is
virtually nil.



...... Phil

 

[Eeyore]

"Michael A. Terrell" wrote:

Here is the donkey's 'Civilized World'

http://www.dailymail.co.uk/news/article-1103843/Boozy-Britains-bloody-New-Year-A-999-seven-seconds-alcohol-induced-mayhem.html

At least we don't kill thousands of our fellow citizens each year with GUNS.

I'd rather have a bloody nose than be dead from a gunshot thanks, you bunch of criminally retarted cunts. At least it's ONE thing
you lead the world at !

http://www.gun-control-network.org/GF01.htm

Graham

 

[Archimedes' Lever]

On Sat, 3 Jan 2009 10:28:53 +0000, tony sayer <tony@bancom.co.uk> wrote:

In article <jevql4tu0q5sb3f8mmta5g5f7d25nml5og@4ax.com>, Archimedes'
Lever <OneBigLever@InfiniteSeries.Org> scribeth thus
On Fri, 2 Jan 2009 02:25:48 -0000, "Phil McKerracher"
usenet@mckerracher.net> wrote:


It's true that isolation is not important for a well-insulated telephone.


A 10kV arc from a 2MV lightning strike *COULD* make it all the way into
the handset, and OUT of the perforations in the handset, through the
earpiece or mouthpiece, and hit the user. The microphone and the
earpiece transducer both use metal cans, making the distance to the user
a mere 1/4" through air. Not good.

This is ONE of the many reasons that isolation elements are
incorporated at VARIOUS locations in the system. One of which is at the
CABLE connection to the phone itself, which is why isolation elements can
be found at these positions. This is a standard element of device design
where human contact is present, and has nothing to do with it being in a
plastic case. It isn't your Dad's AC fed two wire drill motor with an
un-phased power cord and metal case. It is, however, in close
(electrical) proximity (potentially) with lightning events, and that is
why arresting elements have been incorporated.

Most incorporations are overkill, as it were, but I am happy that our
scientists and engineers of decades past were concerned about such
things.

Idiots today seem to think everything is low voltage and harmless.

Ummmm....

A standard UK BT NTTP socket as used for the UK POTS would have a gas
tube arrestor -across- the line. IIRC there is a centre tapped point
which might be earthed, but in most all cases won't be;-(..

So several miles of OHL and just that and an -out of service- resistor
doesn't seem like much effective protection to what nature can
deliver....

You left out the isolation transformer in the phone.

Also, the tube will have a return path, and quell any HV down to
non-arcing voltages.

 

[Archimedes' Lever]

On Sat, 3 Jan 2009 23:04:50 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"Archimedes'= CRIMINAL PSYCHOPATH "


** Report this FUCKING SCUMBAG to his ISP

NOW !!!!!!!!!!!!!!!!


Get the STINKING PIG fucked off usenet for ever.





..... Phil

Yes, Phil... the fucking scumbag, stinking pig that you are should
have complaints filed against him.

I agree... Folks... please file complaints about the stupid, group
abusing poster that we all know of as:

The EverVile PhilTard!

 

[Archimedes' Lever]

On Sat, 3 Jan 2009 23:05:43 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"Archimedes'= CRIMINAL PSYCHOPATH "


** Report this FUCKING SCUMBAG to his ISP

NOW !!!!!!!!!!!!!!!!


Get the STINKING PIG fucked off usenet for ever.





..... Phil



Hey, Phil, you fucking retard! You have been DOUBLE POSTING all of your

retarded tripe to the group TWICE.

You are about as stupid as a Usenet poster can get, but I assure you
that Roy has you beat.