MoIP: How do we make modem calls over IP? (and general chat about phone networks and modems, T1, E1, BRI 56k etc)

[famicomaster2]

Just my two cents: While it would definitely be challenging, reinventing the wheel might make sense here.

I.e. simulate the phone line/call (like you would for tcpser or a similar situation), answer it, and then do the demodulation step yourself. Then you can forward purely digital data over the regular internet to a similar setup on the other end (whatever that happens to be).

Although UDP/IP might be a better starting point than TCP/IP because of all the extra overhead doing send/resend and error correction.

Since it isn't a true voice call you shouldn't need to capture and reproduce the whole spectrum of frequencies.

Using ATA and VoIP forces you to understand a lot of complex stuff that is/was used to provide functionally similar telephone service via the internet.

While that does make some things easier it also introduces it's fair share of problems and dilemmas

What you are describing is ISDN over IP which already exists and is an absolutely fantastic solution for exactly this. The problem is that the hardware is rather expensive and PSTN services that support it are hard to find and expensive. They're also not exactly what I'd call easy to set up.

 

[famicomaster2]

So, here's a "Version 2" setup. An Adtran Total Access 908e (3rd gen) now fulfills the IAD role, supplanting both the Patton SmartNode 4960 and Virtual Console PSTN Simulator. A Patton 2960 RAS has been added to (eventually) replace the Patton 2800 that sits outside of the photo, but both are currently connected to the TA908e for a combined 72 digital modems.

385-596-1770 - 10 channel trunk, Patton 2800, V.34 -> Telnet Gateway
385-596-1771 - 10 channel trunk, Patton 2960, V.92 -> Telnet Gateway
385-596-1772 - 10 channel trunk, Patton 2960, V.92 -> Telnet Gateway
385-596-1773 - 10 channel trunk, Patton 2960, V.92 -> Telnet/PPP
385-596-1774 - 10 channel trunk, Patton 2960, V.92 -> Telnet/PPP

How did you get the Adtran to give you multiple numbers for the PRI ports? When I set one number, any port connected will take a call from that number.
I've personally been unsuccessful in getting the SIP side of my Adtran working, but I still have a connection to the PSTN from my home landline.

Wow, those Virtual Console simulators are super expensive. I really want one of their BRI-PRI converters but I just can't justify $2500 for a new one. The last used one went for $400 and it sold within seconds of being listed.

The Patton 2800, while V.90-capable, has been intentionally constrained to V.34 (33.6 kbps) because V.90 (and V.92) connections are difficult to maintain across VoIP links. The Patton 2960 is currently uncapped (full V.92) for now, though I may cap it at 43.4 kbps later.

Why 43.4 specifically? That's an odd value.

The "Telnet Gateway" service will accept any Telnet-accessible host and, optionally, a port value. This is similar to the service that https://2600.network provides, but differs in that I didn't want to manage a list of BBSes and credentials on the RAS itself and am instead just forwarding to a Raspberry Pi for both the gateway script and Telnet host resolution. The maximum session time is set to 120 minutes.

My 2960 was sourced from the admins at 2600, who begrudgingly sold it to me for $1000 a few months back. And that's a pretty raggedy, beat up 2960/16.

 

[famicomaster2]

So, which is better ? On one hand, 56K would be a marginal advancement from V.34 since only the download speed is affected (the Dialogic is V.90-capable, but not V.92, software limatation).

Almost nothing is v.92 capable. It was a real quest to get my setup going. Neither the Eicon Divas nor the Dialfire 2977 support v.92 - i.e. there is no way to get it on a PCI card to stick in a computer. Unless someone writes some new DSP code to support it (entirely possible), it doesn't exist.

And also, as Cloudschatze stated, V.90/V.92 connections are hard to sustain over VoIP (I plan to connect the card to an Asterisk server in the same computer). On the other hand, the Multitech card has V.92-capable modems which benefit from V.44 compression in both ways, upload and download !

Is v.44 valid compression for any analog connection other than when linked to a v.92 host? I've never seen it active in any other case than connected to my Dialfire.

 

[famicomaster2]

Data Connect for the 2810 ($350), and a private sale for the 2960 (which was "priced per the last eBay listing" at $750).

Keep in mind that Data Connect now wants deep 4 figures for a 2810 and triple that for a refurb base model 2960.
Patton Electronics is still around and still refurbishes Dialfires among other hardware, but they will not sell to anyone other than through Data Connect. They are the dealer and whatever price they say goes.

One of the only Patton Dialfire I see available on eBay is a 2977 PCI card, at ~420USD.

The Dialfire 2977 is a renamed Digi Datafire, which you can probably find for cheaper under that name instead of Patton, but still nowhere near as cheap as the Eicon Divas. None of them will do v.92 anyways so there is no advantage to the Patton/Digi card other than brand name and driver preference.
The Eicons can do some cool stuff like be an IVR or voicemail and mass faxing, among other things, with the software.

 

[Neoa_56]

You can use plain CT1 as well

Very, very few BRI devices contain the brains to answer an analog call. The US Robotics Courier I-Modems (rare and expensive in many cases) can do v.90 and X2 with a proprietary license someone had to buy before the service went down, the Eicon Diva BRI cards have the DSPs to do analog calls, and the Tyan Netscalibur can do v.34.

The Adtran makes it dirt simple to set up and it's extremely reliable. They're also fanless, run pretty cool, and pretty cheap. I don't know about the Ciscos but I've heard they often have noisy fans and are rather power hungry. The Adtrans have a GUI setup as well, if you don't like a CLI.

I recently acquired 2 internal European I-Modems (17€ on Vinted with another modem) and a Dialogic Diva 4BRI-8 (~30€ on eBay), my wish is to integrate everything in a single computer with Asterisk and 56K/33.6K dial-up.

It's still not clear if Digium FXS cards are capable of handling 56K, though.
There may be another solution, as there is a post of someone on Reddit (currently discussing with them) using an I-Modem as the 56K digital modem and as the TA for the analog modem, on a Digium B410P ISDN Asterisk card.
If Asterisk doesn't work, I'll just buy some cheap Siemens or Panasonic PBX, probably a KX-TDA15/30 or an HiPath 3000/5000

 

[Neoa_56]

Keep in mind that Data Connect now wants deep 4 figures for a 2810 and triple that for a refurb base model 2960.
Patton Electronics is still around and still refurbishes Dialfires among other hardware, but they will not sell to anyone other than through Data Connect. They are the dealer and whatever price they say goes.


The Dialfire 2977 is a renamed Digi Datafire, which you can probably find for cheaper under that name instead of Patton, but still nowhere near as cheap as the Eicon Divas. None of them will do v.92 anyways so there is no advantage to the Patton/Digi card other than brand name and driver preference.
The Eicons can do some cool stuff like be an IVR or voicemail and mass faxing, among other things, with the software.

The only advantage of Patton/Digi cards is K56Flex support I guess.

 

[maxtherabbit]

The US Robotics Courier I-Modems (rare and expensive in many cases) can do v.90 and X2 with a proprietary license someone had to buy before the service went down,

It would be amazing if someone who had the skillset cracked this. It was done back in the day for the analog couriers and sportsters

 

[Neoa_56]

Almost nothing is v.92 capable. It was a real quest to get my setup going. Neither the Eicon Divas nor the Dialfire 2977 support v.92 - i.e. there is no way to get it on a PCI card to stick in a computer. Unless someone writes some new DSP code to support it (entirely possible), it doesn't exist.

Is v.44 valid compression for any analog connection other than when linked to a v.92 host? I've never seen it active in any other case than connected to my Dialfire.

With 2 laptops (V.92 winmodems) on my Siemens HiPath 1120 PBX

 

[Neoa_56]

It would be amazing if someone who had the skillset cracked this. It was done back in the day for the analog couriers and sportsters

You can still download the V.90 firmwares for USR I-Modems : https://binaryfury.wann.net/2025/05/finding-old-ftp-usr-com-us-robotics-support-files/

 

[maxtherabbit]

You can still download the V.90 firmwares for USR I-Modems : https://binaryfury.wann.net/2025/05/finding-old-ftp-usr-com-us-robotics-support-files/

the method described in the article for downloading the files did work for me, one must wonder for how long though

 

[Cloudschatze]

How did you get the Adtran to give you multiple numbers for the PRI ports? When I set one number, any port connected will take a call from that number.
I've personally been unsuccessful in getting the SIP side of my Adtran working, but I still have a connection to the PSTN from my home landline.

I hope I'm not misunderstanding the question, but the DIDs are provided through Anveo Direct, and the trunk groups were configured on the Adtran to accept call patterns per the following:

voice grouped-trunk "PATTON 2960 TRUNK"
trunk T01
trunk T06
accept 385-596-177[1234] cost 0
accept 1-385-596-177[1234] cost 0

voice grouped-trunk "PATTON 2800 TRUNK"
trunk T02
accept 385-596-1770 cost 0
accept 1-385-596-1770 cost 0

The further delineation between the "Telnet Gateway" and "Telnet/PPP" access on the 2960 is accomplished via DNIS Profiles.

I have the SIP side working well for outbound stuff (through Anveo Direct) and even SIP pairing with another device. I'd be happy to share more of the configuration, or the entire thing, if that would be helpful.

Why 43.4 specifically? That's an odd value.

I encountered the 43.4 kbps reference in some Avaya documentation and figured it might be more generally applicable. I haven't tested it yet though, so it may very well be as much a misadventure as the higher V.90/92 rates have been.

 

[famicomaster2]

I recently acquired 2 internal European I-Modems (17€ on Vinted with another modem) and a Dialogic Diva 4BRI-8 (~30€ on eBay), my wish is to integrate everything in a single computer with Asterisk and 56K/33.6K dial-up.

Yes, the Courier I-Modem is a very flexible unit, they're highly sought after. I had to pay through the nose for my two internal units, and I had to import my two external units from France. Still having difficulty getting BRI in my home network - I have a pair of Teltone ILS units (a 1000 and a 2000) but they cannot call out to the rest of my network, sadly.

It would be amazing if someone who had the skillset cracked this. It was done back in the day for the analog couriers and sportsters

I'm told some Russian website had a proper crack for it, but I have been unable to locate a copy. All of the ones in my collection already have the upgrade license.

With 2 laptops (V.92 winmodems) on my Siemens HiPath 1120 PBX

Interesting! I did not know you could use v.44 on other connections. This is very useful.

You can still download the V.90 firmwares for USR I-Modems : https://binaryfury.wann.net/2025/05/finding-old-ftp-usr-com-us-robotics-support-files/

The firmware is to upgrade X2 licensed units to support v.90 - It does not activate the X2/v.90 license if you do not already have it. Applying this update to a modem without the license get you the code to actually do v.90 but the feature is still disabled.

I hope I'm not misunderstanding the question, but the DIDs are provided through Anveo Direct, and the trunk groups were configured on the Adtran to accept call patterns per the following:

Ah, I am not attached to SIP on my Adtran. When assigning an ISDN number plan, it applies to all active PRI NT ports. I am calling port to port on FXS, out to the PRI for the Dialfire, and I have a VoCa FXO provided by the cable company which lets me answer and originate outside calls. I have a second VoCa line not attached to the Adtran right now because it does not support pulse dialing and that bothers me. Still looking for a viable replacement PBX.

I encountered the 43.4 kbps reference in some Avaya documentation and figured it might be more generally applicable. I haven't tested it yet though, so it may very well be as much a misadventure as the higher V.90/92 rates have been.

Interesting, I haven't heard anything like that. I have heard that lots of people have very good luck getting 28.8 over VoIP connections reliably, but that the more optimized Trellis pattern for 33.6 often fails.

 

[Neoa_56]

Yes, the Courier I-Modem is a very flexible unit, they're highly sought after. I had to pay through the nose for my two internal units, and I had to import my two external units from France. Still having difficulty getting BRI in my home network - I have a pair of Teltone ILS units (a 1000 and a 2000) but they cannot call out to the rest of my network, sadly.


I'm told some Russian website had a proper crack for it, but I have been unable to locate a copy. All of the ones in my collection already have the upgrade license.


Interesting! I did not know you could use v.44 on other connections. This is very useful.


The firmware is to upgrade X2 licensed units to support v.90 - It does not activate the X2/v.90 license if you do not already have it. Applying this update to a modem without the license get you the code to actually do v.90 but the feature is still disabled.


Ah, I am not attached to SIP on my Adtran. When assigning an ISDN number plan, it applies to all active PRI NT ports. I am calling port to port on FXS, out to the PRI for the Dialfire, and I have a VoCa FXO provided by the cable company which lets me answer and originate outside calls. I have a second VoCa line not attached to the Adtran right now because it does not support pulse dialing and that bothers me. Still looking for a viable replacement PBX.


Interesting, I haven't heard anything like that. I have heard that lots of people have very good luck getting 28.8 over VoIP connections reliably, but that the more optimized Trellis pattern for 33.6 often fails.

You might be interested in a Siemens HiPath PBX, they can do FXS and BRI for pretty cheap (<200€ for a HiPath 3500 or OpenOffice ME with a few BRI and FXS cards)
It can also have a T1/E1 trunk card, one per system afaik.
I'm probably buying one soon, it seems that they can also connect to an ITSP to provide dial-out and dial-in.

Regarding V.44, I talked about the Multitech ISI5634 before because it would be useful to have V.44 compression available on connections that can't sustain a 56K link (mainly dial-in users, outside of the PBX)

About the I-Modems, don't they all support X2 ? My units are from '97, and they seem to be from the "second gen" with "ISDN with V.EVERYTHING" marked on the box, rather than "ISDN with V.34"

 

[famicomaster2]

You might be interested in a Siemens HiPath PBX, they can do FXS and BRI for pretty cheap (<200€ for a HiPath 3500 or OpenOffice ME with a few BRI and FXS cards)
It can also have a T1/E1 trunk card, one per system afaik.
I'm probably buying one soon, it seems that they can also connect to an ITSP to provide dial-out and dial-in.

Interesting. Can they do BRI NT or the US ISDN protocols? (5ESS, DMS100, NI1)
I don't own anything that will work with E1, only T1/PRI. Two of my BRI modems can use international signalling, but the other 10 can't, so I definitely need that. None of them will work as anything *but* TE though, so whatever I connect them to needs to act as NT.

Sadly, they're not cheap here. Most of the base configuration ones I'm seeing are $500+ and don't have the cards I'd be looking for.

Regarding V.44, I talked about the Multitech ISI5634 before because it would be useful to have V.44 compression available on connections that can't sustain a 56K link (mainly dial-in users, outside of the PBX)

About the I-Modems, don't they all support X2 ? My units are from '97, and they seem to be from the "second gen" with "ISDN with V.EVERYTHING" marked on the box, rather than "ISDN with V.34"

Interesting. Both of mine say "ISDN with v.34" on the front.

 

[RetroAND]

Hello,

I am very interested in this matter, but unfortunately I haven't known the golden age of modems, just the final part when they were finally replaced.

I would like to build the infrastucture to host a legacy HTTP site for Dreamcast.

What would be required?

Thank you in advance and sorry for my ignorance

 

[mR_Slug]

I believe there is already a product that does exactly this. If you want to make it yourself you may want to look at that for the server. Hardware wise you need another modem set to receive and a PBX. Everything can be analog and simple. The PBX can be replaced by a line simulator, if all you want is a 1-to-1 modem connection.. Really depends on how much hardware you want, and/or integrate it into an existing phone system. Voip ATAs can be used as a PBX too. Anything BRI, PRI, ISDN, T1, E1 is digital and you can ignore.

 

[famicomaster2]

Hello,

I am very interested in this matter, but unfortunately I haven't known the golden age of modems, just the final part when they were finally replaced.

I would like to build the infrastucture to host a legacy HTTP site for Dreamcast.

What would be required?

Thank you in advance and sorry for my ignorance

A project exists called DreamPi which allows you to connect your Dreamcast to a USB modem attached to a Raspberry Pi. Hosting a legacy HTTP site is trivial and can be done with any one of hundreds of free hosting tools.

DreamPi Tutorial : Dreamcast Live

DreamPi is a piece of software created by Luke Benstead a.ka. Kazade that allows you to get your Dreamcast online. The software runs on a Raspberry Pi, which is essentially a tiny computer and turns a standard broadband internet connection into a dial-up connection that can be used by the...

dreamcastlive.net

If you want faster than 33.6K you will need to either get a Dreamcast ethernet adapter (the easy and cheap route) or do as Mr Slug suggests and set up a proper PBX or equivalent with a digital RAS of some kind. Highly complicated and expensive for your purposes.

 

[maxtherabbit]

If you want faster than 33.6K you will need to either get a Dreamcast ethernet adapter (the easy and cheap route)

At ~$200 I wouldn't call that cheap. But a BBA is really nice to have for save file management to a PC over the LAN and for ripping games.

 

[RetroAND]

A project exists called DreamPi which allows you to connect your Dreamcast to a USB modem attached to a Raspberry Pi. Hosting a legacy HTTP site is trivial and can be done with any one of hundreds of free hosting tools.

DreamPi Tutorial : Dreamcast Live

DreamPi is a piece of software created by Luke Benstead a.ka. Kazade that allows you to get your Dreamcast online. The software runs on a Raspberry Pi, which is essentially a tiny computer and turns a standard broadband internet connection into a dial-up connection that can be used by the...

dreamcastlive.net

If you want faster than 33.6K you will need to either get a Dreamcast ethernet adapter (the easy and cheap route) or do as Mr Slug suggests and set up a proper PBX or equivalent with a digital RAS of some kind. Highly complicated and expensive for your purposes.

I don't mind the low transfer speed. Thank you all!

 

[Neoa_56]

Interesting. Can they do BRI NT or the US ISDN protocols? (5ESS, DMS100, NI1)
I don't own anything that will work with E1, only T1/PRI. Two of my BRI modems can use international signalling, but the other 10 can't, so I definitely need that. None of them will work as anything *but* TE though, so whatever I connect them to needs to act as NT.

Sadly, they're not cheap here. Most of the base configuration ones I'm seeing are $500+ and don't have the cards I'd be looking for.

I'm not really well versed in ISDN protocols
I suppose they only do Euro-ISDN, their BRI cards have "S0" marked on them (S/T bus).
There is also a card for T1 access, it will only work if your device can act as a TE (same goes for the E1 access card).
Do you know of any other "PBX" options with lots of BRI/FXS + a few T1/E1s other than Adtran 550/830/890s ?