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Possible Duplicate:
How to boost audio volume coming from a telephone

Foreword: If you don't know the answer, don't leave. Write your idea where I could find an answer to this as a comment.

I want to connect my telephone to my computer's sound card. I want to connect my headset to my computer's line-in with a mic preamplifier in between. I want to hear my partner on the phone and talk to him using my cable headset connected to my computer.

The reason for me to connect my computer's sound card to my phone is that I want to include music samples into my voice channel so my partner I am talking to via phone can hear my voice aswell as music samples generated by my computer.

How would you do that. Be as precise as possible.

What kind of phone? This landline cable-bound phone. enter image description here

What headset?

Something like that

enter image description here

What have you tried?

A lot. I won't share it to avoid influencing the ideas.

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    \$\begingroup\$ You be precise first. What kind of phone? Cellular? Voip? Landline? Skype? Google Voice? What headset? What handset? What have you tried? \$\endgroup\$
    – Jim Paris
    Oct 7 '12 at 2:18
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    \$\begingroup\$ If a bbertrager is a transformer then the circuit you posted a link to in a semi random comment location will NOT work on a phone line but may work on a headset connection - it assumes a headset socket with send and receive "ports" on the 4 wire connection. Top of diagram is incoming audio from line and bottom is og audio to line. Use some hardwrae guy's cct as basic idea. Can buy surplus for small amount. Can just couple to line with TWO capacitors plus series resistors. Illegal (probably) potentially life threatening. Chep. May work. Transformer adds needed isolation to keep you alive. \$\endgroup\$
    – Russell McMahon
    Oct 7 '12 at 3:17
  • \$\begingroup\$ Your diagram shows 2 devices labelled "bbertrager". You may or may not what they are. Certainly, very few other people will. Supplying a diagram in English, where possible, is probably wise. If a bbertrager in the circuit you posted a link to is a transformer then the circuit will NOT work on a phone line but may work on a headset connection. The circuit assumes a headset socket with send and receive "ports" on the 4 wire connection. Top of diagram is incoming audio from line and bottom is o/g audio to line. \$\endgroup\$
    – Russell McMahon
    Oct 7 '12 at 22:31
  • \$\begingroup\$ Use user "some hardware guy"'s circuit as abasic idea, as he says he has done it and it works. You can buy surplus devices that do exactly what he shows for a small amount. || You CAN just couple to line with TWO capacitors plus series resistors but this is illegal (probably) & potentially life threatening. Also cheap, and it may work. A transformer adds needed isolation to keep you alive. \$\endgroup\$
    – Russell McMahon
    Oct 7 '12 at 22:32
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Not so hard I've built that before :) Long time ago though. Anyway first you can buy things like this if you want. Here's one that's not cheap but pre - built.

http://www.jkaudio.com/voice-path.htm

If you want to do it yourself you just need a hybrid transformer and a few parts. Check out this website it has a couple of schematics that will do the job. Especially look at the one titled "Recording interface from Tekniikan Maailma magazine"

http://hackipedia.org/Protocols/Telephone,%20POTS/html/teleinterface.html

enter image description here

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  • \$\begingroup\$ and how do you dial a number without a phone? Or is this parallel to the phone so I dial using the phone and then I use my soundcard to "talk". I thought about connecting the 4p4c-socket of the phone with the soundcard. Also your circuitry jkaudio.com/voice-path.htm does not work with my intended goal. \$\endgroup\$ Oct 7 '12 at 2:29
  • \$\begingroup\$ Also: Does this work in germany aswell? What are the requirements regarding the phone line? \$\endgroup\$ Oct 7 '12 at 2:35
  • \$\begingroup\$ I have this idea: mikrocontroller.net/attachment/156738/aktuelleSchaltung.gif Does this work aswell? \$\endgroup\$ Oct 7 '12 at 2:38
  • \$\begingroup\$ I think that circuit just attaches in parallel to your phone line. So you use your regular phone to dial (thought that's what you were looking for?) I've never made equipment for Germany but yeah I think this should still work. \$\endgroup\$ Oct 7 '12 at 3:30
  • \$\begingroup\$ Maybe we can make my approach ( mikrocontroller.net/attachment/156738/aktuelleSchaltung.gif ) work aswell as it is now all soldered but I can't get sound out of it at all. Some details: Goal is to have a max of 3 Volts output at the headphones, the phone supplies 77mV AC at 400Hz. So 77mV are to be amped up to about 2.8 Volts with a audio transformer in between. \$\endgroup\$ Oct 8 '12 at 0:33

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