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Asterisk with modems instead of phonecards

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Anonymous
January 24, 2005 7:08:26 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

Hello everyone,
I'm a newby

My company does not want to invest in FX0 cards for an office with two
phones. We already have some modems though.

Is it possible to setup Asterisk linux PBX with four modems (two for pstn
two lines, and two for inside phone cables going to phones), and then
through Asterisk make that work?

Or this could be even better if Asterisk server would have two modems
connecting to PSTN lines and act as a gateway for two IP phones via tcp/ip.

Thanks a Lot!
Anonymous
January 24, 2005 8:03:52 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

> Is it possible to setup Asterisk linux PBX with four modems (two for pstn
> two lines, and two for inside phone cables going to phones), and then
> through Asterisk make that work?

The short answer is, no.
Anonymous
January 25, 2005 12:08:10 AM

Archived from groups: comp.dcom.voice-over-ip (More info?)

>> Is it possible to setup Asterisk linux PBX with four modems (two for pstn
>> two lines, and two for inside phone cables going to phones), and then
>> through Asterisk make that work?

>The short answer is, no.

The slightly longer and more correct answer is yes.

Make sure that you realize what "modem" means in this case. For connection
to the PSTN you'll need an "FXO" device and for connection to the telephones
you'll need "FXS" devices. There are more or less standard modems which
will do some of this. (I have used a Digium X100P modem with Asterisk.) I
recommend sticking with things that are designed to work with Asterisk.

The Digium product to do this all on one card is the TDM400P. (I have one.)
You'd then add two FXS and two FXO modules for a cost of over $300.
http://store.yahoo.com/asteriskpbx/tdtd2fxspo2f.html

I hate the sloppiness that results from connecting to a POTS line and I've
found my IP phones and Sipura devices to be much more satisfying so I don't
use Digium hardware anymore.

--kyler
Related resources
Anonymous
January 25, 2005 1:59:23 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

Thanks!

Ok, to simplify this, can i achieve the following:
Build an Asterisk Server with one SIP IP phone connected inside and an
outside phone line connected to a standard external modem, so that Asterisk
would be a PSTN gateway for that One phone?


"Kyler Laird" <Kyler@news.Lairds.org> wrote in message
news:6m2gc2-p55.ln1@lairds.us...
> >> Is it possible to setup Asterisk linux PBX with four modems (two for
pstn
> >> two lines, and two for inside phone cables going to phones), and then
> >> through Asterisk make that work?
>
> >The short answer is, no.
>
> The slightly longer and more correct answer is yes.
>
> Make sure that you realize what "modem" means in this case. For
connection
> to the PSTN you'll need an "FXO" device and for connection to the
telephones
> you'll need "FXS" devices. There are more or less standard modems which
> will do some of this. (I have used a Digium X100P modem with Asterisk.)
I
> recommend sticking with things that are designed to work with Asterisk.
>
> The Digium product to do this all on one card is the TDM400P. (I have
one.)
> You'd then add two FXS and two FXO modules for a cost of over $300.
> http://store.yahoo.com/asteriskpbx/tdtd2fxspo2f.html
>
> I hate the sloppiness that results from connecting to a POTS line and I've
> found my IP phones and Sipura devices to be much more satisfying so I
don't
> use Digium hardware anymore.
>
> --kyler
Anonymous
January 25, 2005 1:59:24 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

"acc admin" <cci-acc.admin@cciholdings.com.au> writes:

>Build an Asterisk Server with one SIP IP phone connected inside and an
>outside phone line connected to a standard external modem, so that Asterisk
>would be a PSTN gateway for that One phone?

Again iff you use the right modem, sure, it's no problem. The X100P is one
such modem. At only $30 there's not much point in messing around with other
modems.
http://www.digitnetworks.com/store/product_info.php?pro...

Also consider a Sipura SPA-3000. I suspect it'll do all that you want for
only $100.
http://store.voxilla.com/customer/product.php?productid...

--kyler
Anonymous
January 25, 2005 1:59:24 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

acc admin <cci-acc.admin@cciholdings.com.au> wrote:
> Ok, to simplify this, can i achieve the following:
> Build an Asterisk Server with one SIP IP phone connected inside and an
> outside phone line connected to a standard external modem, so that Asterisk
> would be a PSTN gateway for that One phone?

What do you mean by "standard external modem"? If you mean a 2400bps Hayes
MNP, then the answer is no. There are very few (if any) data modems that
provide satisfactory full-duplex voice operation. The chance that you will
happen to have one lying around without having bought it for that purpose is
quite low.

miguel
--
Hit The Road! Photos from 35 countries on 5 continents: http://travel.u.nu
January 25, 2005 5:18:58 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

mnc@admin.u.nu (Miguel Cruz) wrote in
news:jeKdnQEfsbYlamjcRVn-2A@speakeasy.net:

> acc admin <cci-acc.admin@cciholdings.com.au> wrote:
>> Ok, to simplify this, can i achieve the following:
>> Build an Asterisk Server with one SIP IP phone connected inside and
>> an outside phone line connected to a standard external modem, so that
>> Asterisk would be a PSTN gateway for that One phone?
>
> What do you mean by "standard external modem"? If you mean a 2400bps
> Hayes MNP, then the answer is no. There are very few (if any) data
> modems that provide satisfactory full-duplex voice operation. The
> chance that you will happen to have one lying around without having
> bought it for that purpose is quite low.
>
> miguel

Silly Questions #2

If i have a user with a analog modem can he dial out through *?

If I wanted to present myself as a dial up solution for low price, could i
purchase a "local" number in another area and have that user modem in to my
* and route that call to a computer on my network? I know my h.323 ATA is
really dsesigned to handle a fax machine, and that is a half duplex modem
for all intents and purposes.
Anonymous
January 25, 2005 8:12:24 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

syd <syd_at_klassifiedbbs_dot_net> wrote:
> If i have a user with a analog modem can he dial out through *?

You don't need asterisk for that; just script it in your favorite language.

> If I wanted to present myself as a dial up solution for low price, could i
> purchase a "local" number in another area and have that user modem in to my
> * and route that call to a computer on my network?

I think you'll have trouble routing modem calls over VoIP links. Anyway,
it's a very inefficient way of doing things. Just make a deal with one of
the zillions of companies bulk-selling dialin services. You definitely can't
compete with them; their margins are tiny.

miguel
--
Hit The Road! Photos from 35 countries on 5 continents: http://travel.u.nu
Anonymous
January 25, 2005 9:13:52 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

> Again iff you use the right modem, sure, it's no problem. The X100P is
> one such modem. At only $30 there's not much point in messing around with

I thought (hey I could have been wrong, but it appears I was not) by modem
he was saying any modem. This question comes up ten times a day in the
mailing list and on IRC and it almost always means "I have a modem [voice
modem, several modems] can I use this with *

The answer is, no.
Anonymous
January 26, 2005 6:08:09 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

syd <syd_at_klassifiedbbs_dot_net> writes:

>If i have a user with a analog modem can he dial out through *?

Sure, analog modems can handle data fast enough for some voice calls.

>If I wanted to present myself as a dial up solution for low price, could i
>purchase a "local" number in another area and have that user modem in to my
>* and route that call to a computer on my network?

You can use any (PPP/SLIP/...) IP connection to your Asterisk box for voice
calls as long as the connection provides sufficient bandwidth for the codec
you use and has latency you find satisfactory.

--kyler
Anonymous
February 4, 2005 6:33:55 PM

Archived from groups: comp.dcom.voice-over-ip (More info?)

"Miguel Cruz" <mnc@admin.u.nu> wrote in message
news:jeKdnQEfsbYlamjcRVn-2A@speakeasy.net...
> acc admin <cci-acc.admin@cciholdings.com.au> wrote:
> > Ok, to simplify this, can i achieve the following:
> > Build an Asterisk Server with one SIP IP phone connected inside and an
> > outside phone line connected to a standard external modem, so that
> > Asterisk would be a PSTN gateway for that One phone?
>
> What do you mean by "standard external modem"? If you mean a 2400bps
> Hayes MNP, then the answer is no. There are very few (if any) data
> modems that provide satisfactory full-duplex voice operation.

There is a basic misunderstanding here. The cards that may act as FXO
interfaces are so-called Winmodems (or Linmodems when used under Linux):
devices where most of the encoding/decoding work when acting as modems is
actually done by the CPU under the control of a device driver, and by a
DSP also loaded with firmware by the device driver. Writing a suitable
alternate device driver, one can give those cards a new lease of life as
FXO interfaces towards POTS lines.

Unfortunately, the characteristics of those cards vary from model to
model, so there is no way of writing a universal driver for all the
existing Winmodems. The Zaptel drivers for Asterisk include one (wcfxo.c)
that works for two models: one, called by Digium X100P, based on a
Motorola SM56 chipset (PCI ID: 0x1057, 0x5608); and another one, called by
Digium X101P, based on an Intel chipset with TigerJet Network Tiger
300/320 PCI interface (PCI ID: 0xE159, 0x0001). For any other Winmodem
card, you are on your own...

Enzo
!