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conkhicon
Joined: 31 Aug 2004
Posts: 106
Helped: 3
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 09 Sep 2004 10:11 Bi-directory Amplifier in Telephone |
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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.
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 09 Sep 2004 16:18 Re: Bi-directory Amplifier in Telephone |
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| 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.
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papyaki
Joined: 13 Apr 2002
Posts: 564
Helped: 19
Location: A small village somewhere in Gaul
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| 09 Sep 2004 20:10 Re: Bi-directory Amplifier in Telephone |
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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
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conkhicon
Joined: 31 Aug 2004
Posts: 106
Helped: 3
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| 10 Sep 2004 2:20 Re: Bi-directory Amplifier in Telephone |
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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.
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 10 Sep 2004 3:11 Re: Bi-directory Amplifier in Telephone |
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| conkhicon wrote: |
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.
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wky
Joined: 23 May 2003
Posts: 163
Helped: 82
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| 10 Sep 2004 6:34 Re: Bi-directory Amplifier in Telephone |
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| If you are talking about SLIC (Subscriber Line Interface Circuit), you can google it and find a lot of infos.
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conkhicon
Joined: 31 Aug 2004
Posts: 106
Helped: 3
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| 10 Sep 2004 9:14 Re: Bi-directory Amplifier in Telephone |
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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....
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radiohead
Joined: 13 May 2004
Posts: 326
Helped: 21
Location: Heart of Europe
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| 13 Oct 2004 17:21 Re: Bi-directory Amplifier in Telephone |
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| 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.
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