telephone lines

luca7300@yahoo.it

Hi ------
Just a simple question.....
How a telephone tx rx works???...I mean how 1 pair of conductor in
the
telephone can trasmitt and recive simultaneously audio
signals......????(if I understood well the pair trasmitt and at the
same time it recives signals)
How a single couple of wire tx and rx?????
many thanks
jac

Graham

<> wrote in message
news:1177587301.389146.89810@r35g2000prh.googlegro ups.com...
> Hi ------
> Just a simple question.....
> How a telephone tx rx works???...I mean how 1 pair of conductor in
> the
> telephone can trasmitt and recive simultaneously audio
> signals......????(if I understood well the pair trasmitt and at the
> same time it recives signals)
> How a single couple of wire tx and rx?????
> many thanks
> jac


Its actually very easy to achive.

When I was a child I wired two telephone handsets
together to make an intercom. The two carbon transmitters
And the two earpieces and a battery were all wired in
series. Yes it worked but not very well. You could hear
your own voice in the receiver just as loud as the other
party, telephone engineers call this excessive sidetone.

The trick is to use a transformer arrangement or an
electronic circuit that cancels your own voice to a
large extent, a small amount of sidetone is desirable.
Its all connected with correct impeadence matching,
Google the word "hybrid" in this context.

--
Graham.
%Profound_observation%