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!

Reply to
acc admin
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The short answer is, no.

Reply to
BlueRinse

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.

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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

Reply to
Kyler Laird

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

Reply to
Miguel Cruz

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.

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Also consider a Sipura SPA-3000. I suspect it'll do all that you want for only $100.
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--kyler

Reply to
Kyler Laird

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?

Reply to
acc admin

snipped-for-privacy@admin.u.nu (Miguel Cruz) wrote in news: snipped-for-privacy@speakeasy.net:

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.
Reply to
syd

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

Reply to
Miguel Cruz

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.

Reply to
BlueRinse

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.

Reply to
Doug McIntyre

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

Reply to
Kyler Laird

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

Reply to
Enzo Michelangeli

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