vgetty / vm shell programming Q

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Bjoern --

Bjoern Giesler wrote:

> Still, isn't it at all possible to somehow reliably detect when a phone
> has gone off-hook on the other side? E.g. would it be possible to start
> recording right after dialing, and analyzing the signal to check if it's
> a human voice or anything else on the other end? It wouldn't even be
> necessary to detect voice/fax/data; just to see if anything else than the
> "dialing" beep pattern is on the line.

I something like this.  I set the VRA/VRN delays to 0, started recording right
after dialing, waited
for the modem to detect silence.  I had to be recording to get silence
detection--just sent
it to /dev/null.  On the US Robotics and ZyXEL modems this was worse than using
the ringback
detection for determing when someone answered the phone.  Silence detection takes
several
seconds--so again there is a delay--and if you set the delay too short the modem
detects silence
between the ringbacks before anyone answers.  Also silence detection can be fooled
by
background noise--if I had music playing the modem would not detect silence.  You
can
control the sensitivity, but it all just seemed too unreliable.

Perhaps your Diamond SupraExpress 56e Pro modem can detect voice on the line and
that might work better than silence detection.  I don't think the modems I have
can do that.
You could try analyzing the recording yourself as it comes in and see if you can
distinguish
ringbacks from voice from silence--a challenge.

I decided that to really do this properly would require better hardware, like a
Dialogic board,
which supposedly can detect when the phone is picked up.  I have not pursued it
that far.

>  What's much more evil is that my modem doesn't stop dialing --
> it just reports ERROR, but keeps on calling. (It's a Diamond SupraExpress
> 56ePro.)

Don't know about that.

-- Al