Why not use a voice modem as FXO card?

Discussion in 'VOIP' started by John Doe, May 1, 2006.

  1. John Doe

    John Doe Guest


    I browsed through the archives, but didn't find a very good
    explanation as to why we can't use a good voice modem as FXO card for
    small setups (read: cheap).

    Is it because their CODECs suck, or they don't support enough of them?

    John Doe, May 1, 2006
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  2. ----- Original Message -----
    As far as I know, most (all?) voice modems are half-duplex: they can send
    or receive voice, but can't do both things at the same time. Moreover,
    their codecs are usually based on some variant of ADPCM, and the driver
    should transcode the data into some other format suitable for VoIP. All in
    all, it's just not worth the trouble.

    On the other hand, some Winmodems (or Linmodems, if we prefer a
    Penguinically-correct designation ;-) ), i.e. data modems where the data
    modulation/demodulation is offloaded to the CPU, can be adapted as FXO
    cards just rewriting their software drivers. This is not trivial
    (requiring the knowledge of the specific hardware) but was done by Digium
    for two models, one based on a Motorola chipset and another on an Intel
    chipset. They used to be sold under the names "x100p" and "x101p"
    respectively. Digium has now discontinued them, but there are still
    several third-party vendors of compatible hardware: just check the hits at
    http://www.google.com.hk/search?q=x100p .

    See also: http://www.voip-info.org/tiki-index.php?page=X100P+clone

    Enzo Michelangeli, May 1, 2006
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  3. John Doe

    John Doe Guest

    On Mon, 1 May 2006 15:27:30 +0800, "Enzo Michelangeli"

    Thanks for the links. I'm about to order a couple of those X10?p cards
    for my first test Asterisk setup, and see how they fare.
    John Doe, May 1, 2006
  4. Raqueeb Hassan, May 1, 2006
  5. John Doe

    John Doe Guest

    John Doe, May 1, 2006
  6. John Doe

    rochanan Guest

    I dont think its impossible. I read somewhere that Intel 537 chipset
    modems can function as an FXO. But I havent tried that out myself.
    But at the moment I have sucessfully used a hardware modem (not a
    softmodem) as a full duplex VOIP-PSTN gateway, that can route calls.
    (Usually the modem's audio driver is half duplex.)

    rochanan, May 1, 2006
  7. John Doe

    John Doe Guest

    Cool. Reference? Support for caller ID? :)
    John Doe, May 2, 2006
  8. John Doe

    Rochana N Guest

    Rochana N, May 2, 2006
  9. John Doe

    John Doe Guest

    John Doe, May 2, 2006
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