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Phone to sound card interface

Discussion in 'Electronic Design' started by Chaos Master, Apr 30, 2004.

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  1. Chaos Master

    Chaos Master Guest

    Hello people

    I'd like to connect a standard phone to the microphone input and speaker output
    of my _PC sound card_ (no modem involved) to make using "Internet phone"
    software more pleasant to use.

    What type of circuit do I need for this purpose?


    Chaos Master® - Posting from Brazil - MSN:
    BRASNET: Wizard_of_Yendor at #POA, #Canoas, #XLinuxNews
    "Eu logo sem dar... mas cada um faz o que quer."
    -- Wagner Shimatai no
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    NP: C:\Meus Documentos\Downloads\linkin park - numb.mp3
  2. Chaos Master

    Chaos Master Guest

  3. hamilton

    hamilton Guest

    $109USD !!!!!

    Someone must have a schematic available for this.

    Any ideas ??

  4. Plenty as I am using VOIP via the PC, but I have a headset.
    Also a mike at thye keyboard..
    Handsfree, you can do other things while listening.
    Why want a normal phone? I think these suck.
  5. hamilton

    hamilton Guest

    The OP and I are interested in using a REAL telephone handset.

    I know its not Kool as a handsfree setup. But its what we want.

    thanks for trying anyway.

  6. Chaos Master

    Chaos Master Guest

    Jan Panteltje bleeding:
    It is to make things more "user-friendly" to peoples that are not used with a PC

    I am using MSN Messenger to do voice chat.

  7. OK, many years ago I did some sort of thing like that.
    You would need a small 48 V DC generator ciruit (published a 1 transsistor
    circuit here several times that could be used for that), a series resistor
    to limit the of-hook current, and then you need some circuit that prevents
    the signal send to the phone appearing a lot in the signal from the phone.
    (You have to substract the two).
    This can be done with a special transformer, but also electronically with an
    opamp circuit.
    Leaving out the ring tone generator..
    Hope I remembered that right.
  8. look up Lundahl transformers,
    they do a phone hybrid transformer, I used to use much cheaper OEP
    transformers, and a 1K pot, and crockclips


    Yesterday it worked.
    Today it is not working.
    Windows is like that.
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