Getting matching transformer from telephone

[Eeyore]

It has everything to do with the information we are
discussing.

You don't know the difference between telegraph wire and
telephone wire, just for starters.

Quite so !

If that was in reference to the previous paragraph of
yours, then you should have put the information there.
In that case I would have jumped all over your claim
that it makes a difference for the 600 mile distance
mentioned when in fact it is not 600 miles *per* *section*.

You also apparently don't know what "repeater stations"
are when dealing with analog carrier systems.


You sent them that distance via FDM carrier systems, not
via landlines, even in the 1930's.


Twisted pair cables are not 600 Ohms.

Absolutely not. About 100 ohms.

Open wire might be though... ;-)


By and large? And 75 Ohms??? (Please don't try buzz words...)


Thank you. (I'm familiar with BT, which evolved from
the General Post Office.)

Via 'Post Office Telecommunications'.

Your problem is that you just don't actually understand
the telephone system, at all.

He has made that evidently apparent.

Graham

 

[Eeyore]

WRONG!!!!!

RIGHT !

Do the damn sums.

Graham

 

[Eeyore]

Impedance for an un-loaded pair varies with frequency. So at DSL
frequencies the impedance is 100 to 110 Ohms.

Correct. It is in fact the classic 'characteristic impedance'.

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

Only on long circuits which were treated differently.

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.

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.

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.

How do the clowns think they determine ON and OFF HOOK ?

Graham

 

[Eeyore]

"Bill Janssen"

** Huh ??

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

I think he was having a laugh !

USA and back via either underground cable or satellite can (did) do some weird
stuff, but even that has gone now with IP telephony which is becoming near
universal now. I can make certain calls to the USA from the UK for LESS than the
cost of certain types of UK call.

In fact a US call for me from the UK to a landline OR CELLPHONE costs 7.5c to
connect and 1.5c / minute.

Graham

 

[Eeyore]

"Lostgallifreyan"

** Oxygen thieves like this anencephalic turd need shooting.

I have to agree.

Plus think of the advantage in reduction of methane emissions !

Graham

 

[neon]

that is a lame idea transformers isolate and pass maximumn power if matched so what a phone is not exactly an good audio anything. Get smart use an photoisolator for that kind of ideas.

 

[krw]

What meds are YOU on ?

Metoprolol and aspirin why? Is your inferriority getting the better
of you again?

 

[krw]

So much donkey arrogance, so little intelligence.

s/arrogance/dung/

 

[Eeyore]

So much donkey arrogance, so little intelligence.

So, go on Mr Expert. Why is one *needed* ?

Graham

 

[Eeyore]

[email protected] says...

Metoprolol

US trade name.

Beta blocker ! Ticker problem ? Not surprised with your temper.

and aspirin why? Is your inferriority getting the better of you
again?

Mine are MUCH more exciting ! Hopefully the physio (suspected trapped
nerve) will remove the need for the opiates.

Going in for a CT on 14th Jan too btw. They're really giving me the
working over this time. And all for FREE on the National Health System !
You might learn something from that. Hillary's not wrong.

Graham

 

[Eeyore]

Alexander Graham Bell despised optocouplers

He didn't have the opportunity, as they didn't exist in his lifetime.

History's never been your strong suit has it ?

Graham

 

[Eeyore]

The transformers are made of plastic??? (I don't think so...)

The PHONES - STUPID ! Even when they bakelite, I doubt it was a good conductor
of electricity.

Graham

 

[Eeyore]

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.

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

Graham

 

[Eeyore]

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.

Graham

 

[Eeyore]

[email protected] (Floyd L. Davidson) wrote:
:>Archimedes' Lever wrote:
:>> [email protected] (Floyd L. Davidson) wrote:
:>> >
:>> >As far as it being a matching transformer, the line
:>> >impedance varies typically from perhaps 100 Ohms all the
:>> >way up to perhaps 2000 Ohms... but you will not find
:>> >anything in a telset to adjust it to match. That's because
:>> >nobody cares if it is even close to matching the line
:>> >impedance.
:>>
:>> Which is why I stated its primary purpose as being that of isolation
:>
:>What exactly needs isolating from what ? Have you noticed they tend to be
:>made of plastic ?
:
:The transformers are made of plastic??? (I don't think so...)
:
: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").

The hybrid in a POTS phone can have all windings effectively connected in
series. It is the polarity of the windings and the relative impedances and the
connections of the transmitter, receiver and balance impedance which effectively
provide for SIGNAL ISOLATION (ie. NOT galvanic isolation) depending upon whether
the telephone is transmitting or receiving. The windings don't have to be
galvanically isolated to do this.

Sense at last !

Graham

 

[Eeyore]

I do not recall giving it the moniker of "isolation transformer". I
merely mentioned the function of electrical isolation.

Which is NOT required.

Graham

 

[Eeyore]

** God, you are one STUPID PIG IGNORANT PUKE !

http://en.wikipedia.org/wiki/Isolation_transformer

http://en.wikipedia.org/wiki/Galvanic_isolation

...... Phil

You know Phil, there are times I really have to agree with you 101%.

Graham

 

[Eeyore]

[email protected] says...

You forgot; "A place that would shame Ali-baba & his 40 thieves",

I have found ebay to be an EXCELLENT place to shop. Many of the best
deals are to be had there. Why run a shop with overheads when you can do
it all online and they even provide the invoicing tools !

And I know shops who do have traditional outlets AND they sell on ebay
too, often at a lower cost. Saved someone several pounds exactly that
way recently in fact.

Graham

 

[Eeyore]

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 ?

Graham

 

[Eeyore]

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 ?

Graham