Re: flexfax: modem 1000$ question

["Jay R. Ashworth" <jra@baylink.com>]

On Mon, Sep 13, 1999 at 06:08:20PM +0100, Darren Nickerson wrote:
> >Seriously; almost every faxmodem built in the last 10 years has known
> >to send those automatically when originating calls in fax mode.  It's
> >so automatic that I don't even know that there's a knob to adjust it.
> 
> Nice try, but slightly incorrect. Some modems do have switches to disable CNG. 
> Multitech, for instance, use the @ at the end of the dialstring. Take the 
> following line from the class2 config file:
> 
> # We normally append the "@" symbol to the dial string so that
> # the modem will wait 5 seconds before attempting to connect
> # and return result codes that distinguish between no carrier
> # and no answer.  This makes it possible to avoid problems with
> # repeatedly dialing a number that doesn't have a fax machine
> # (kudos to Stuart Lynne for this trick.)

Note that the phrasing of that trick agrees with my memory of the
character's behavior: it causes a delay, not the disabling of the CNG
tones.

Most faxmodems, in fact, send the calling tones from the time they're
done dialling.

Interesting side note:

Last week, on a new install (which generated a question I asked here,
and don't remember seeing an answer on, BTW -- I guess I better check
and see what I wanted to know :-) I had a _very_ interesting problem.

The problem turned out to be another fax modem on the same line,
hearing the CNG tones on the line _even though it was on-hook_,
assuming there was an _incoming_ call, and answering -- about the same
time the modem I was _dialling_ answered.  I don't have to explain how
messy this was, do I?

Apparently some modems can listen for CNG on the line before answering,
to allow them to distinguish incoming fax calls, which they should
answer, from incoming voice calls, which they shouldn't.

Inasmuch as most CO switches no longer send transmit audio until the
call is answered, I don't see why this might be useful, but what they
hey...

Cheers,
-- jra
-- 
Jay R. Ashworth                                                jra@baylink.com
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