Bi-directory Amplifier in Telephone

[conkhicon]

I am designing a device in telephone line. VoiceSignal is transmit from A to B and B to A in the same as line.
Please tell me link or schema which is discussed about Bi-directory Amplifier.

 

[flatulent]

This is 70 year old technology. The device which splits the two way signals to one each one way signal is called a hybrid. They are made with two transformers with center taps.

 

[papyaki]

Hi,

Look at this application note. It give a very good schematic of phone line interface :

h**p://www.midcom-inc.com/tech/tn88.htm

* = t

 

[conkhicon]

Hi flatulent
You say true!
But it's is 2 to 4 wires. Transmit line is difference in receive line. I need transmit and receive in the SAME line. No hibrid.
That is a technical of 21th century., I hope.

 

[flatulent]

Hi flatulent
You say true!
But it's is 2 to 4 wires. Transmit line is difference in receive line. I need transmit and receive in the SAME line. No hibrid.
That is a technical of 21th century., I hope.

What you do is put these circuits back to back so that on the four wire side you have the amplifiers going in each direction. that is you split to 4 wires for the amplifiers and then back to two wires for the main line each side out.

 

[wky]

If you are talking about SLIC (Subscriber Line Interface Circuit), you can google it and find a lot of infos.

 

[conkhicon]

Hi flatulent
This is theory solution!
Assume 2 branchs are A and B. When A is role Amplifier and the same time B will be a part of position feedback -> Echo -> create electric oscillation
I think that invert phases 180 degree of one of A or B -> negative feedback -> atenuation (not gain!). And in practise not exactly for invert 180 degree.
Please tell me how....

 

[radiohead]

Flatulent is completely right. The problem here is to design a very good hybrid, with very high return loss. This way the echo's are very small, loop gain is lower than 1 and oscillation cannot occur.