asterisk users - Dec 2003 - Slightly OT and mildly insane: Modems through VoIP :-))

Hi,

First off, let me state that _YES, I am fully aware that what I am doing is 
insane, prone to major havoc and bad for general health_ :-))

Scenario: My GF needs an analog modem to use with her banking software 
(sodding backs don't supply a decent web-application for company use). I am 
experimenting to see if we can get it to work (albeit slow) trough our ATA186 
talking g711 to Asterisk with chan_capi to the outside world. Should we fail, 
there are more sane alternatives, but humour me :-))

Now, with some modems on the other end I have received nice 26400bps 
handshakes, but it takes a long time and the successrate is about 25% :-) My 
feeling is this should be better if we choose to slow it down more. 

But who can tell me what the best modem settings would be to try ? My HAYES 
dialect is rather old :-))

Any experiences or hints are appreciated.

-- 
Best regards,
Florian Overkamp

On Mon, 2003-12-15 at 16:13, Florian Overkamp wrote:
> Hi,
> 
> First off, let me state that _YES, I am fully aware that what I am doing is
> insane, prone to major havoc and bad for general health_ :-))
> 
> Scenario: My GF needs an analog modem to use with her banking software 
> (sodding backs don't supply a decent web-application for company use).
I am
> experimenting to see if we can get it to work (albeit slow) trough our
ATA186
> talking g711 to Asterisk with chan_capi to the outside world. Should we
fail,
> there are more sane alternatives, but humour me :-))
> 
> Now, with some modems on the other end I have received nice 26400bps 
> handshakes, but it takes a long time and the successrate is about 25% :-)
My
> feeling is this should be better if we choose to slow it down more. 
> 
> But who can tell me what the best modem settings would be to try ? My HAYES
> dialect is rather old :-))
> 
> Any experiences or hints are appreciated.
While playing around for a while back on my cable modem with the adit600
and a T100P doing IAX to my PRI in the office, I was lucky to get 14400
V42bis and keep it very long. The longer you are connected, the worse it
would get till it finally gave up.

What you may need to do is fake the modem out. Hook a null modem to your
GF machine and tell the banking software to use a standard 14400 modem
connected to the serial port. Connect the other side to your linux
machine and log what comes in on the port. Then figure out if it is just
attempting to make a ppp connection to the net and access something on a
globally accessible IP address. If so, hook up pppd to the port and let
the banking software muddle it's way through your linux machine much
like I used to do with my TiVo.  

I used my TiVo like that for almost 2 years before the latest software
update killed my account with TiVo. Updates where less annoying over
cable modem than over 14400 modem.
-- 
Steven Critchfield  <critch@basesys.com>

> Message: 2
> Date: Mon, 15 Dec 2003 23:13:46 +0100
> From: Florian Overkamp <florian@obsimref.com>
> To: asterisk-users@lists.digium.com
> Subject: [Asterisk-Users] Slightly OT and mildly insane: Modems through
VoIP :-))
> Reply-To: asterisk-users@lists.digium.com
>
> Hi,
>
> First off, let me state that _YES, I am fully aware that what I am doing
is
> insane, prone to major havoc and bad for general health_ :-))
>
> Scenario: My GF needs an analog modem to use with her banking software
> (sodding backs don't supply a decent web-application for company use).
I
am
> experimenting to see if we can get it to work (albeit slow) trough our
ATA186
> talking g711 to Asterisk with chan_capi to the outside world. Should we
fail,
> there are more sane alternatives, but humour me :-))
>
> Now, with some modems on the other end I have received nice 26400bps
> handshakes, but it takes a long time and the successrate is about 25% :-)
My
> feeling is this should be better if we choose to slow it down more.
>
> But who can tell me what the best modem settings would be to try ? My
HAYES
> dialect is rather old :-))
>
> Any experiences or hints are appreciated.
>
> -- 
> Best regards,
> Florian Overkamp
>
I've made data calls over g.711 voip from australia to the uk and they
trained up to 31k2 fine. What will throw them is packet loss. Just one lost
20ms frame was normally enough to force a retrain. Lose a packet during
retraining and the call would probably drop. Might pay to check the duplex
settings on your ata and whatever its connected to.
echo cancellers could possibly interfere with things but they should be
disabled by the 2100hz tone at the front of the call.

cheers,
darren