Getting matching transformer from telephone

[Floyd L. Davidson]

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

Salmon Egg wrote:
For a long time I believe the term actually used for this transformer
was "induction coil."

Now we're getting to the point.

'Loading coils' were used to boost voice levels on long line circuits by
loading the line to compensate for line capacitance IIRC.

Loading coils are not the same as induction coils.

NOT needed in your average city. And certainly NOT a *transformer*.

Both are actually tranformers though. And, BTW, they were indeed
used in "your average city".

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

 

[Floyd L. Davidson]

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

"Floyd L. Davidson" wrote:

Salmon Egg <SalmonEgg@sbcglobal.net> wrote:
floyd@apaflo.com (Floyd L. Davidson) wrote:

A telephone loop has both VF (voice frequency) and DC
signals going in both directions, all of which need to
be "isolated" from each other. The transmit and receive
VF signals also have to be isolated from each other
(which is why the transformer is commonly called a
"Hybrid Network").

For a long time I believe the term actually used for this transformer
was "induction coil."

They are commonly called either "induction coil" or
"repeat coil". However, the ones used in the type of
telephone you would commonly see (in a home or business)
are generally encapsulated, and include a balance
network, midpoint capacitor, and possibly other
components, and is usually but not always called a
"network" of some kind.

Equipment seen in a telephone office would more likely
have been built with individual components, and at least
up into the 1970's would have had a separate transformer
that would indeed have been labeled as "Ind. Coil" or
"Rep. Coil". At least for WECo built equipment that
would have been true, and others at times did the same
or came up with something different just to be
different.

Complete overbuild. You should see a 'BT' one made by GEC or Plessey. No
such things.

As if you had a clue.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

 

[Floyd L. Davidson]

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

"Floyd L. Davidson" wrote:

What the phone is made of is not important in any way to this
conversation.

Really ?

Have you ever heard of conductors and non-conductors ?

I've also heard of semi-conductors. But my statement still
stands.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

 

[Floyd L. Davidson]

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

"Floyd L. Davidson" wrote:

"Phil Allison" <philallison@tpg.com.au> wrote:

The fact that phones are made of plastic IS the damn reason that GALVANIC
isolation from the phone line is not required.

That is one of the best bits of humor I've seen in some time on
this group. Nice post. I was rolling on the floor laughing.

I'm laughing at YOU !

Have you NO understanding how phones work ? Apparently NOT ! Ringing voltage is
around 100V AC or chopped DC. How's your matching transformer going to deal with
THAT ?

With relative ease. Want to see another schematic? Do you need
someone to explain it to you? (Get 'em Mike!)

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

 

[Floyd L. Davidson]

Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

Eeyore wrote:

"Floyd L. Davidson" wrote:

"Phil Allison" <philallison@tpg.com.au> wrote:

The fact that phones are made of plastic IS the damn reason that GALVANIC
isolation from the phone line is not required.

That is one of the best bits of humor I've seen in some time on
this group. Nice post. I was rolling on the floor laughing.

I'm laughing at YOU !

Have you NO understanding how phones work ? Apparently NOT ! Ringing voltage is
around 100V AC or chopped DC. How's your matching transformer going to deal with
THAT ?

http://en.wikipedia.org/wiki/Ringing_voltage#Ringing_signal

Astounding.

But, all I'ver ever read about it before was in things like
Bell Standard Practices, and various telecom engineering texts.

Did you want me to edit the wiki page to make it more precise,
or what?

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@apaflo.com

 

[Michael A. Terrell]

"Floyd L. Davidson" wrote:

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

"Phil Allison" <philallison@tpg.com.au> wrote:

The fact that phones are made of plastic IS the damn reason that GALVANIC
isolation from the phone line is not required.

That is one of the best bits of humor I've seen in some time on
this group. Nice post. I was rolling on the floor laughing.

I'm laughing at YOU !

Have you NO understanding how phones work ? Apparently NOT ! Ringing voltage is
around 100V AC or chopped DC. How's your matching transformer going to deal with
THAT ?

With relative ease. Want to see another schematic? Do you need
someone to explain it to you? (Get 'em Mike!)

Floyd, no matter what you show the 'Doubtful Demented Donkey' he will
insist that it is wrong, because 'It isn't done that way in England'.
Even when shown official British documents he calls them fabrications.

The nonexistent 'transformer' in the common 500/2500 family of US
telephones was used for cheap phone patches as well as remote control of
commercial two way radio systems over leased copper telco pairs for
generations.

He claims to be the world's top EE in audio mixing console designs,
yet he can't understand an early C.O. powered desk set. For evidence,
he doesn't understand how the ringing signal can be on the same pair as
the DC and audio. It was brilliantly simple use of a pair of thin
copper wires and copied worldwide, but he only sees Chinese phones from
the British equivalent of a dollar store.

His small mind would implode over a simple 1A2 system of 17 lines and
a couple hundred phones, yet almost anyone could be taught to install
and configure them. As long as they weren't color blind and could
count, that is. You can imagine what would happen if he ever walked
into a working '50s era electro-mechanical C.O.


The 'Deliriously Demented Diseased Dumbass Donkey' suffers from a
severe hatred of the US, and anything developed here. He is the butt of
thousands of 'D' jokes on the electronics newsgroups because of his
claims to have the highest IQ, yet he has never mastered the 'savant'
part of his being an 'idiot savant'.

He always chooses kiddy porn screen names that imply he is not even a
teenager.


--
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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.

 

[Archimedes' Lever]

On Wed, 31 Dec 2008 09:42:18 +0000 (GMT), Stuart <Spambin@argonet.co.uk>
wrote:

In article <87zlidi9tr.fld@apaflo.com>,
Floyd L. Davidson <floyd@apaflo.com> wrote:
"Don" <me@ntlworld.invalid> wrote:
In news:5015e0eccbSpambin@argonet.co.uk,
Stuart <Spambin@argonet.co.uk> typed:

What was the "test match" effect?


I'm intruiged! Go on - tell us!

This should be real interesting...

I'm waiting to see your guesses to *both* questions

Hint: both answers relay on the fact that the lines are straight analogue
from end to end.

Freudian shlip? 'relay'? rely

 

[Keith]

On Wed, 31 Dec 2008 20:04:59 -0500, "daestrom"
<daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:

krw wrote:
In article <oqydnaMeppa09cbUnZ2dnUVZ_gidnZ2d@earthlink.com>,
mike.terrell@earthlink.net says...

Eeyore wrote:

"Michael A. Terrell" wrote:

Now, you are catching on. Eeyore is a british idiot

Your ignorance stands out like a shining beacon on a dark night.

There never was or has ever been a need for a transformer in a
phone.


So much donkey arrogance, so little intelligence.

s/arrogance/dung/

Wouldn't the correct syntax be:

s/arrogance/dung/g

Could be. My backgound isn't DEC, rather IBM, so...

?? So it replaces more than one occurance on each line??

....where your version would be "c/arrogance/dung/al"l. However there
was only one occurance in the post I was replying to.

Sed, gotta love it

;-)

 

[GS]

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:eoidnU2FHLVbacbUnZ2dnUVZ_rLinZ2d@earthlink.com...

If the National Health System was any good you would be committed for
poor mental health.

Free isn't the same as compulsory...not yet anyway...

--
GS
reverse org.microhero@graham to reply

 

[Michael A. Terrell]

GS wrote:

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:eoidnU2FHLVbacbUnZ2dnUVZ_rLinZ2d@earthlink.com...


If the National Health System was any good you would be committed for
poor mental health.


Free isn't the same as compulsory...not yet anyway...

They are still softening you up to accept it.


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

aioe.org, Goggle Groups, and Web TV users must request to be white
listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in
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.

 

[Archimedes' Lever]

On Thu, 01 Jan 2009 12:27:01 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

GS wrote:

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message
news:eoidnU2FHLVbacbUnZ2dnUVZ_rLinZ2d@earthlink.com...


If the National Health System was any good you would be committed for
poor mental health.


Free isn't the same as compulsory...not yet anyway...


They are still softening you up to accept it.

I thought that was what the country was doing to us by putting Obama in
office.

Softening us up for the royal screwing we are in the process of
getting.

 

[Paul B]

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
made possible by the fact that UTP cable bandwidth has
improved to match the baseband of television signals. While
the video recorder most likely still has unbalanced BNC
connectors for standard coaxial cable, a balun is used to
convert from 100-ohm balanced UTP to 75-ohm unbalanced."

*** 100-ohm balanced UTP ***

I seem to remember from another time that Old Floyd worked for
some Alaskan phone company..

Anyways what was the original question .. seems to have fallen
off the news server?...

A slightly obscure question as to effectively (not sure if the
OP realised) whether impedance or voltage matching was
important. Needless to say, many IDIOTS think everything audio
HAS to be 600 ohms which is an irrelevant ancient standard
anyway but lingers on in the minds of the long brain-dead.

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.

Telephones seem to suppress line noise and hum rather well so I
figure the components they use are probably of half-decent
quality.

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

Graham

Right..

Wonder what's he actually trying to do .. in practice?..

If he's still there?...

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.


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.

 

[Archimedes' Lever]

On Fri, 02 Jan 2009 00:32:00 GMT, Paul B <mail@nomail.invalid> wrote:

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

According to Roy, you want a ground loop.

He is such an electrical genius!


NOT!

bwuahahahahahahahahahahahahaha!

 

[Phil Allison]

"Paul B"

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.

** Hey pal.

YOU already know what to do ( ie use a proper 600:600 ohms ISOLATION
transformer or a device incorporating same) ) and are just objecting to a
price of a few pounds or dollars.

Make you a fucking PITA wanker.

FUCK OFF.



...... Phil

 

[Phil McKerracher]

Interesting thread (not the childish abuse, the technical stuff!). I didn't
know that loading coils were so common in the US, for example.

My twopenn'orth, as someone who has designed line interface circuits in the
past:

Bill Janssen wrote:

Eeyore wrote:
...the phone should be a
reasonable match to the line to minimize refections which bother the
users as
echoes...

This is true - someone (not sure who, sorry) commented earlier that this
doesn't matter because the speed of light is so high, and that's true for
local calls but not for long distance ones. These days there is packet delay
to worry about as well. There are echo cancellers but they're not perfect.
Mismatches also affect loudness.

The transformers in some sets was not an isolation transformer but a
hybrid and matching transformer.

Only ever seen that in a fax machine I helped develop for Xerox (RXEG) and
the
hybrid part was done with differential amps, NOT the transformer. MUCH
cheaper.

It's true that isolation is not important for a well-insulated telephone.
It's also true that differential amps are a cheap alternative to
transformers for the hybrid part. But I have definitely seen phones with
transformers in them in the past (the 80s). And I have designed interfaces
myself (for modems) that used transformers in preference to op amps because
of their superior common mode rejection, isolation and (electrical)
robustness.

I have never seen a transformer in ANY phone including the carbon mic type
which
also 'draws power from the line' to power the mic as you say.

I have, from the days before transistors - they were specially constructed
to tolerate DC current without saturating the core or overheating.

--
Phil McKerracher
www.mckerracher.net

 

[Archimedes' Lever]

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.

 

[Phil Allison]

"Phil McKerracher"

Interesting thread (not the childish abuse, the technical stuff!).

** So you post more tech BS & childish stuff - great .

Bill Janssen wrote:

...the phone should be a
reasonable match to the line to minimize reflections which bother the
users as echoes...

This is true ...

** Make sure you get attributitions correct - pal.


- someone (not sure who, sorry) commented earlier that this

doesn't matter because the speed of light is so high, and that's true for
local calls but not for long distance ones.

** The comment was:

" Audible echoes on a few miles of twisted pair ??? "

Which excludes all longer lines, of course.

These days there is packet delay to worry about as well. There are echo
cancellers but they're not perfect. Mismatches also affect loudness.

** But *audible echoes* on a line are not caused by transmission line
behaviour.

They are caused by problems with the hybrid to line impedance match so that
signals get retransmitted back to the exchange PLUS there has to be a
significant time delay caused by a very long link - ie thousands of miles.

It's true that isolation is not important for a well-insulated telephone.
It's also true that differential amps are a cheap alternative to
transformers for the hybrid part. But I have definitely seen phones with
transformers in them in the past (the 80s).

** What you claim you saw without proof is irrelevant

- seen any Martians lately ?

Exceptional cases are also irrelevant to the original matter.

And I have designed interfaces myself (for modems) that used transformers
..

** Modems are not the topic.

Different animals to ordinary phones.



...... Phil

 

[Phil Allison]

"Archimedes' Wanker = total Fuckwit "

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.

** Plus it would jump across the insulation barrier in a 600 ohm line
isolation tranny too !!

FUCKWIT !

This is ONE of the many reasons that isolation elements are
incorporated at VARIOUS locations in the system.

** Surge voltage clamping is not "isolation" - FUCKWIT !!

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.

** Surge voltage clamping is not " isolation " - FUCKWIT !!

Most incorporations are overkill,

** Shame one has not killed you then - FUCKHEAD.




....... Phil

 

[Archimedes' Lever]

On Fri, 2 Jan 2009 13:57:33 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

** Plus it would jump across the insulation barrier in a 600 ohm line
isolation tranny too !!

FUCKWIT !

Except that they ALSO incorporate yet another arrestor at the service
entry. Nice try though... nice sig too... Fits you to a tee.

 

[Phil Allison]

"Archimedes' Wanker =Total Fuckwit "

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.

** Plus it would jump across the insulation barrier in a 600 ohm line
isolation tranny too !!

YOU LYING FUCKWIT !

This is ONE of the many reasons that isolation elements are
incorporated at VARIOUS locations in the system.

** Surge voltage clamping is not "isolation" - FUCKWIT !!

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.

** Surge voltage clamping is not " isolation " - FUCKWIT !!

Most incorporations are overkill,

** Shame one has not killed you then -

you fucking oxygen thief.



....... Phil