Asterisk with modems instead of phonecards

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!

 

Is it possible to setup Asterisk linux PBX with four modems (two for pstn

The short answer is, no.

 

Is it possible to setup Asterisk linux PBX with four modems (two for pstn

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

 

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?

 

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/...id=28&osCsid=1299284a1df25dfed74c951d57ba64f2

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=16144&cat=0&page=

--kyler

 

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

 

(Miguel Cruz) wrote in

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.

 

Again iff you use the right modem, sure, it's no problem. The X100P is

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.

 

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

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

 

Modems through VOIP links get at best around 9600-14400 baud
connections before they start crapping out using typical CODECs out there.

Obviously, you'd be restricted to 28800 speeds at best anyway, because
you'd be going through more than the one D/A conversion restriction
that makes 56k modems even work.

Seems like alot to go through just to get something like that.

 

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

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

 

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

 

I'm sorry to ask this and I feel stupid, but...

I have seen many questions and discussions about using an old modem of some kind as an FXO with an Asterisk Setup. I am wanting to know if I can setup Asterisk with an SIP Provider and then use the modem as an FXS to plug my analog phone into. This way I can have the Asterisk Machine connected through Ethernet to my Network and then to the Internet connecting to my SIP Provider and then my Analog Cordless Telephone plugged into the modem. Is this idea crazy? If you can't do this then what kind of equipment do I need to look for to use to plug the analog phone into the the VOIP server? I have just started trying to do this since last night for fun. I am trying to see how far I can take my Google Voice and SIPGate Accounts and what all I can do for free with them. Any help would be greatly appreciated, because at this point I have about 5 hours of experience with this field!!! Thank you very much in advance.

-CHRIS