Re: Linux support for voice modems?

From: John-Paul Stewart (jpstewart_at_binaryfoundry.ca)
Date: 05/05/05

  • Next message: Haines Brown: "Re: Linux support for voice modems?" 
    Date: Wed, 04 May 2005 18:23:06 -0400

    Haines Brown wrote:
    > John-Paul Stewart <jpstewart@binaryfoundry.ca> writes:
    >
    >
    >>But to distinguish before answering (and hence not ring the phone for
    >>a fax) isn't possible without another line or distinctive ring, AFAIK.
    >
    >
    >>I've never seen it done in hardware, but that doesn't mean it can't
    >>be. Software, sure. But that means the computer has to answer *all*
    >>incoming calls and decide what to do. The vgetty docs mention that
    >>briefly, saying that if a non-voice call is detected, vgetty can be
    >>configured to spawn mgetty to handle a data call.
    >
    >
    > So, I infer that while vgetty might discriminate between voice and
    > fax, the phone will ring in either case.

    Correct.

    >>>I use fax too little to make a dedicated line worthwhile, I would
    >>>like to send/receive FAXes from the computer, and I would not want my
    >>>phone to ring if it is only a FAX coming in. Am I dreaming?
    >>
    >>That might be a bit of dream. Have you looked at the full VOCP system
    >>(built atop vgetty and mgetty)?
    >>
    >>http://www.vocpsystem.com/
    >
    >
    > I glanced at this URL, but it did not exactly say there would be no
    > telephone ring with incoming faxes:
    >
    >
    >>When a call comes in and the familiar beep beeps of a fax are
    >>detected, VOCP will correctly stop all voice modem activity and
    >>switch to fax mode (by exiting with a status code that vgetty
    >>recognizes). Mgetty will take the call over, and save the incoming
    >>fax (normally to /var/spool/voice/incoming).
    >
    >
    > I'm not clear whether this "beep beep" is in lieu of a telephone ring,
    > or in addition to the ring. Do you know?

    Yes. It's the first thing after the phone is *answered*. I.e., it
    rings, then something (either the fax machine or you at a telephone)
    answers the call. It's the act of *answering* that starts the sequence
    so there's no way to do anything without ringing (which will, of course,
    ring everything connected to that line---fax machine, modem, telephones,
    whatever).

    >>It won't quite do what you want, but it can come close. You can
    >>either have it answer all calls (voice and fax) and take voicemail or
    >>receive the fax. Or could you could have it answer no calls, and
    >>manually transfer incoming fax calls to the software. There are lots
    >>of possible scenarios that you could configure, but not quite what
    >>you're after.
    >
    >
    > So the VOCP System (open source, for curious lurkers), the choice is
    > between recording all incoming calls, voice or fax, or ring the phone
    > for all incoming calls. The former option would interfere with normal
    > phone operation, it seems.

    Well, you can use it as a digital answering machine. I.e., it's set to
    answer everything after N rings. Either you answer manually before that
    (and re-direct faxes when needed) or it answers and automatically routes
    things. It doesn't really interfere with normal phone operation.

    > Can a FAX machine have phone output jack so that it discriminates
    > between incoming FAX and voice, so that one simply puts fax machine
    > before the DSL adapter?
    >
    > | --> phone
    > incoming --> faxMachine --> DSLadapter |
    > | --> NIC

    That's no different from:

    incoming --> DSL Adapter | --> phone
                              | --> NIC
                              | --> fax machine

    or just about any other arrangement you can imagine.

    Again, the fax machine (like anything else connected to a phone line,
    and whether it is a stand-alone fax machine or a fax-modem) will cause
    the phone to ring for an incoming fax since there is *no way* for
    anything to discriminate between fax and voice until the DTMF tones come
    (which are *after* the line is answered). This is why distinctive ring
    service is so handy. Around here it's only $5-$10/month for the second
    number (which isn't a second line---you can't do fax and voice at once)
    which lets you distinguish by ring pattern whether it is a fax or voice
    call.

    The short version is that you cannot distinguish between fax and voice
    until after the line has been answered, and that pretty much implies
    ringing the phone for faxes. Either spend the money on distinctive ring
    (or a second phone line) -or- accept that incoming faxes will ring the
    phone and manually transfer them via VOCP (or equivalent).

  • Next message: Haines Brown: "Re: Linux support for voice modems?"

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