Getting matching transformer from telephone

In typed:


I'm intruiged! Go on - tell us!
--

Don



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This should be real interesting...
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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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.
--
Stuart Winsor

For Barn dances and folk evenings in the Coventry and Warwickshire area
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"Floyd L. Davidson" wrote:

Quite so !

Absolutely not. About 100 ohms.

Via 'Post Office Telecommunications'.

He has made that evidently apparent.
Graham
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Cable type Impedance at 1000 Hz
19NLS 470 19NLP 262 19H50P 675 16B22 806 19H245S 1882

So have you.
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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"Floyd L. Davidson" wrote:

What kind of screwy cables are those ? 1kHz has NOTHING to do with their characteristic impedance.
Here we use CW1308.
And why the heck do you think ADSL is based around an assumption of typical 100 ohm charactistic cable / line impedance ? http://www.st.com/stonline/products/literature/an/7205.pdf
CRETIN !
Graham
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Speaking of cretins!
The chart is from Bell System documentation (which I cited in another article). If you think the frequency has nothing to do with the characteristic impedance, argue with Bell Labs.
ADSL is based on 100 Ohm impedance for very good reasons. One of them being the frequencies used...
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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Course there are misunderstandings and some terminology shift in broadcast/telecoms and all related to the way various operators used to and now do things etc at different times..
But its all good for a slanging match;)...
--
Tony Sayer


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"Floyd L. Davidson" wrote:

General Post Office.
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"Floyd L. Davidson" wrote:

Which is why it's 100 ohms or so just like Cat 5 etc.
Graham
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Except of course when it has loading coils in it, and then it is something much higher.
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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"Floyd L. Davidson" wrote:

Try running ADSL down a line with loading coils ! There's no need for them anymore. These days you just adjust the line gain.
Graham
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Did you see where it said above... "Telephone cable". Not all telephone cable can run ADSL. (And no you don't "just adjust the line gain".)
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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"Floyd L. Davidson" wrote:

In civilised parts of the world with proper infrastructure it can.
Graham
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How would you know that?
--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson
Ukpeagvik (Barrow, Alaska) snipped-for-privacy@apaflo.com
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"Floyd L. Davidson" wrote:

Jesus Wept !
Graham
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Floyd L. Davidson wrote:

I think he is referring to a part of the world that is about to adopt sharia law..
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Stuart wrote:

They weren't using something that resembles a single pair of Cat 5 back then.
As I said, it's HISTORICAL only and of no practical value.
Graham
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Eeyore wrote:

Impedance for an un-loaded pair varies with frequency. So at DSL frequencies the impedance is 100 to 110 Ohms. But for telephone use They preferred to use loaded pairs and they were designed to be 900 Ohms. And the phone should be a reasonable match to the line to minimize refections which bother the users as echoes
The transformers in some sets was not an isolation transformer but a hybrid and matching transformer. The carbon mic. used in the old phones was powered from the line. And many of the newer phones derive power from the line. So isolation can't be used.
Bill K7NOM
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"Bill Janssen"

** Huh ??
Audible echoes on a few miles of twisted pair ???
The speed of electrical signals must be a * hell of a lot * slower than C where you live - pal.

** At least you do know what an "isolation " transformer is.
Unlike some here.
..... Phil
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