Just recently, there was a surge in traffic to my old legacy dial-up sounds pages. While I did my best with the equipment I had at the time to capture the sound of dial-up modems, I always knew that my job was only half done. As we approach the consumer POTS-line apocalypse, and ISP upon ISP are starting to disable their modem banks, the V.90/V.92 handshake sound is seriously under threat. Anything from V.34bis and down is still safe, since having modems “back to back” will allow for this type of connection to occur, but since V.90/V.92 are digital modulations on the downstream, the digital modems are rare, expensive and require special digital (ISDN or better) connectivity to function. There’s no way most home users can afford to have them. As a result, in this post, I finish the job I started (before it’s too late) to present the definitive collection of V.90/V.92 modem sounds at a quality never previously presented before.
A Two-Paragraph Introduction to Modem History
Early modems used simple modulations involving FSK/PSK modulations and separate carrier frequencies for receive and transmit. When that became spectrally impractical, interim protocols featuring “turn-around” which were half-duplex and various non-standard optimizations started to appear (e.g. Trailblazer, USRobotics HST, Hayes Ping-Pong/Express96). Over time, developments were made which increased the data rate by using more sophisticated Trellis-code modulation, and full-echo cancelling to allow for the full voice-band frequency to be used in both ways simultaneously. This increased the complexity of the modems, which also increased their handshaking times due to the requirement for training, a process whereby the modems assess the qualities of the phone line and set optimal parameters to maximise the transmission rate within a given set of line conditions.
A good introduction to the various sounds of dial-up modems was done in a relatively viral image by Oona Räisänen on her blog, reproduced here under CC:
This image, however, depicts a V.34-type connection, as it has no high speed sound.
The High Speed Sound
This is not the correct technical term for it, but it’s a term which I’ve heard amongst my less technically proficient group of friends. They realized that by listening to the modem’s handshake, there was a particular sound towards the end of the handshake which signalled a high speed connection. They were right.
This sound is of the Digital Impairment Learning (DIL) sequence. This is only applicable for V.90/V.92 connections, as V.34-type (analog, up to 33.6k) connections do not have it. If you heard this “sound”, you would be fairly certain that you were attempting a V.90 (up to 56k) connection.
For those who want a headache, they can go and try to digest the ITU-T’s V.90 recommendation here, specifically the section about DIL (8.4.1) and the section about Signal Ja (8.3.1).
While the document is technical, I will try to explain the concept in a progressively more difficult way. Basically, the standard dictates that the analog modem (customer side) sends a Ja sequence which tells the digital modem (ISP side) what signals to generate for the DIL segment and send back. This allows the analog modem to understand the line parameters better – namely, is there robbed bit signalling (i.e. where one-bit of every six 8-bit frames, or more in case of multiple RBS links, is altered by the signalling equipment), or are there digital pads (i.e. a DSP algorithm based scaler which reduces the maximum level on the phone line). This allows for the modem to adapt and compensate for these impairments.
The signal itself is rather complicated in specifications, consisting of up to 255 segments, 8 codes per segment, with the length in 6-symbol blocks determined by the associated H-value. Further to this, the specifications also define a sign-pattern and training-pattern, which are up to 128 bits long, and specify whether a symbol transmitted is a training symbol or a reference symbol, and whether the symbol has positive amplitude or negative amplitude. This sequence is repeated completely until it is aborted by the analog modem, or the sending modem times out. Further to this, throughout the DIL procedure, the analog modem is also permitted to send scrambled data (SCR), but is not required to do so.
Because of this analog modem defined nature of the DIL signal (i.e. the high speed sound), different modem manufacturers were at liberty to use a different DIL training pattern optimized for their algorithms. This resulted in a case where people would notice that my modem didn’t quite sound like that recording!
As to why this flexibility is in the V.90 standard (and not found in earlier standards) may have to do with the compromise nature of V.90 which came about to end the war between K56flex and X2 by producing an incompatible but similar modulation that modems from both camps could be upgraded to. This flexibility may have been necessary to appease both parties and reduce the engineering effort required to redesign their digital impairment learning algorithms, but that’s just a hunch.
Methodology
In order to capture the best quality handshakes, I had to resort to a necessary evil of VoIP. While generally not optimized for data, I was careful to configure the transmit/receive amplitudes, disable echo cancellation, reduce packetization to 10ms increments, use G.711a codec, disable fax pass-through detections and lock the jitter buffer at its minimum value of 30ms. This made it much more suitable. I terminated my test calls through the Linksys/Sipura PAP2T ATA to a local VSP which has digital terminations I know are capable of returning the exact digital codes and permit a V.90 connection, which is very difficult. Additional V.92 testing was performed using an overseas VSP termination, as local V.92 modem banks that were reachable through VoIP terminations were not known.
The VoIP ATA was connected through a Ethernet bridge where all the packets in both directions were collected and reconstructed into call audio using Wireshark (as PCM 16-bit samples, rather than the native a-law 8-bits). This allowed me to separate digital and analog modems into separate channels. Some echo is heard due to impedance mismatches at the analog end, which is expected behaviour.
This method is much better than recording the audio output from the modem’s speaker jack (as I did previously) as it eliminates power supply and digital hash noise from the recordings, and allows for separation of the two ends of the call. It’s also obviously miles better than recording the audio using a microphone, as the tinny piezo buzzers on many internal modems do a pretty bad rendition of the actual call audio.
Of course, getting the drivers and getting the modems installed was not necessarily trivial especially with some of the less popular and less supported winmodems. This required computers spanning Windows 7 x64, down to Windows 98SE to ensure the functionality of the collection of modems.
The Samples
This is the section you’ve all been waiting for. In this section, we will look at the actual recorded sounds. Before we begin, here’s a few things to look out for (spectrograms generated with Spek):
Some modems perform the V.8bis and escape to V.8 at the beginning of the call, with some of them getting the timings wrong and mucking that up. Others don’t bother at all, and just respond only to V.8, which is possibly slightly faster. Some modems send a guard tone with the data sequences before and after the line probing signal, while others do not, resulting in a slightly brighter sound. The DIL sequences vary between the chipsets, but some have scrambled data being sent back and others do not – so keep an ear out for that as well.
V.90 Handshakes
These will be presented, grouped by chipset. Click on the link text for the audio. Waveform images shown, with green indicating analog modem, and blue indicating digital modem. If you would like to hear just the DILs cut-together into one audio file, here it is. It probably makes an ideal nerdy ringtone, for those who still use a ringtone.
Rockwell/Conexant HCF/ACF/ACF2 Modems
![Conexant-HCF-[smooth-crescendo]](https://goughlui.com/wp-content/uploads/2016/05/Conexant-HCF-smooth-crescendo.png)
Rockwell/Conexant were the most popular chipset as they were relatively low cost solid performers. These could be found in various brands of external and early internal modems. The sound that these produce is arguably the most typical V.90 sound that most people remember, having a smooth crescendo as the DIL. It does not perform V.8bis.
![Netcomm-RoadsterIIUltraSVD-[two-tone-cres]](https://goughlui.com/wp-content/uploads/2016/05/Netcomm-RoadsterIIUltraSVD-two-tone-cres.png)
By all means, this was not the case with all ACF2 modems, but my Netcomm Roadster II 56k UltraSVD (AM5690) and Roadster II USB (AM5050R3) both make this two toned crescendo, which might easily be mistaken for the first. It also has some difficulty during the INFO sequence which causes it to be prolonged. It performs V.8bis.
![Conexant-HSFi-[stuttering-crescendo]](https://goughlui.com/wp-content/uploads/2016/05/Conexant-HSFi-stuttering-crescendo.png)
These were fairly popular internal soft modems and instead use a stuttering crescendo rather than a smooth one. It seems to get the V.8bis timing wrong, and misses the first capabilities request message consistently, which may be a driver bug.
Lucent Technologies WinModem (later known as Agere)
![Agere-Mars1648C-[bipbipbipbip]](https://goughlui.com/wp-content/uploads/2016/05/Agere-Mars1648C-bipbipbipbip.png)
Arguably one of the best softmodems I have used, and one that had kept me online for almost half of my dial-up career. This one uses a “bipping” noise with scrambled data sent during DIL. No V.8bis negotiation takes place. This used the Netcomm IN5699_5 with the latest V8.36 driver, although many products used the 1648C chipset, the last hardware-DSP based generation.
Lucent Technologies WinModem (later known as Agere)
![Agere-Mars-HV90-[bipbipbipbip]](https://goughlui.com/wp-content/uploads/2016/05/Agere-Mars-HV90-bipbipbipbip.png)
This one was recorded using the 1646 HV90 chipset modem running (deliberately) V5.44 driver under Windows 98SE (the things I go to for this). This validated the observation made by Richard Gamburg of Modemsite of DIL changes. The differences can be seen in the tone pattern and scrambled data during the DIL.
Agere Softmodem (later known as LSI)
![Agere-Venus-SV92PP-[echo-blip]](https://goughlui.com/wp-content/uploads/2016/05/Agere-Venus-SV92PP-echo-blip.png)
A relatively unrelated cousin of the LT winmodem, also went through a name change due to a series of acquisitions. It is seen that this modem does not do V.8bis negotiation and does not send scrambled data during the DIL, with a DIL that sounds like an echoing blip. The Broadcom modems also sound identical.
Texas Instruments DSP based Modems
![USR-Sportster-[bong-bong]](https://goughlui.com/wp-content/uploads/2016/05/USR-Sportster-bong-bong.png)
This particular chipset was considered a premium chipset and was part of most of USRobotics’ extremely reliable range of modems, such as the Sportster Flash, Courier, Message Modem etc. I also found the same chipset in an Aztech EM6800U/A and the same line frequency diagnostic command also works (ATY11). The DIL is known affectionately as the “bong”.
Ambient Technologies (later Intel) Modems
![Swann-SpeedDemon-[crackly-buzz]](https://goughlui.com/wp-content/uploads/2016/05/Swann-SpeedDemon-crackly-buzz.png)
This chipset was found in the Swann Speed Demon as well as the Amigo Intel Host-Accelerated Modem. This one makes a crackly buzzing noise, which on tinny piezo speakers, is hard to distinguish from the regular noise of scrambled data. The modem also does not participate in V.8bis negotiations. Not very commonly encountered.
Motorola Hardware/External Modems
![Acer-AcermodemSurf56-[laserbeam]](https://goughlui.com/wp-content/uploads/2016/05/Acer-AcermodemSurf56-laserbeam.png)
This sample was recorded from an Acer Acermodem Surf 56, the only Motorola hardware external modem I have come across. The modem has a very particular DIL sound which I have dubbed the laserbeam and has the honour of being the shortest DIL sequence recorded.
![Motorola-SM56-[laserbeam]](https://goughlui.com/wp-content/uploads/2016/05/Motorola-SM56-laserbeam.png)
The SM56 soft-modem, while also a Motorola chipset, differs from their hardware chipsets in the pace of the DIL. For their soft modems, the DIL sequence is slower and more prolonged. A subtle, but noteworthy difference.
![ESS-Teledrive-[stuttering-bip]](https://goughlui.com/wp-content/uploads/2016/05/ESS-Teledrive-stuttering-bip.png)
A relatively uncommon, low cost soft-modem which had some good opinions from time to time. I’ve never used it, however, its DIL is distinctive with a staccato bipping that makes it sound like someone’s having a seizure or something. It was nice to hear this one as I had never heard this one prior to this investigation.
![Smartlink-SL2800-[smooth-crescendo]](https://goughlui.com/wp-content/uploads/2016/05/Smartlink-SL2800-smooth-crescendo.png)
This modem was an SL2800 modem, but it sounds practically identical to every Smartlink/Modio product I have used. At a time, these were quite popular as a softmodem driver for AMR/CNR based modems in cheaper computers and laptops, and they worked with many integrated audio chipsets. Their crescendo is easily mistaken for a Rockwell/Conexant but is slower.
V.92 Handshakes
V.92 was the last dial-up modem standard, and bought along with it features such as quick connect which at least, in theory claimed to reduce handshaking times by remembering line performance parameters, support for call-waiting modem-on-hold to suspend and resume data connections (although this was rarely allowed by ISPs), PCM upstream for increased upload rates up to 48k at the cost of limiting downstream rate to 48k as well (again, rarely used). It was accompanied by V.44, an improved data compression standard, which was commonly used to improve throughput.
In the course of testing, I also made calls overseas, terminating via a u-law gateway in the USA to their V.92 modem banks. The increased latency makes the connection both difficult, and prolonged, with the handshake signals almost artificially prolonged to lengths not often heard. However, this gave me a chance to capture the quick-connect behaviour of the V.92 capable modems that did successfully exhibit quick connect within the 10-30 test calls I made per modem.
Agere Softmodem Normal V.92 Connect
There’s nothing too flashy about this one, and it doesn’t differ very much to the V.90 connection reported earlier with the exception of increased latency and the ulaw/alaw conversion or mismatch. Regardless, the arrangement was sufficient to demonstrate V.92 connection in normal mode.
Agere Softmodem Quick V.92 Connect
This is where things get interesting. The quick connect recognizes V.92 upfront and skips the line probing sequence entirely. The DIL is still used, but an accelerated version of it is used. This is the first time I have exhibited the one modem using two different DIL sequences. The connect is indeed quicker by a few seconds, although its robustness may be affected.
USR Message Modem Normal V.92 Connect
![USR-Message-V92NC-[bong-bong-bong]](https://goughlui.com/wp-content/uploads/2016/05/USR-Message-V92NC-bong-bong-bong.png)
Because of the latency, the DIL has “looped” around resulting in two-and-a-half bongs in the DIL segment. Normally, hearing four bongs indicates a time-out of the DIL and a retrain occurs, but in this case, the connection is successful as V.92 and the extra partial bong is due to latency of the “abort sending DIL” command.
USR Message Modem Quick V.92 Connect
![USR-Message-V92QC-[bong-bong-bong]](https://goughlui.com/wp-content/uploads/2016/05/USR-Message-V92QC-bong-bong-bong.png)
Again, the line-probing sequence is skipped in the quick connect, as V.92 capabilities are quickly identified, but the DIL in this case remains the normal regular DIL as this modem only has the one DIL sequence.
Motorola SM56 Softmodem Normal V.92 Connect
In the case of the Motorola, the increased latency of the trans-pacific connection gives us an unusual glimpse into its extended DIL sequence. In the case of the USR above, its termination was merely delayed by latency, but in the Motorola, it was delayed more than just by latency revealing more of the DIL which is not normally heard.
Motorola SM56 Softmodem Quick V.92 Connect
![Motorola-SM56-V92QC-extDIL[laserbeam]](https://goughlui.com/wp-content/uploads/2016/05/Motorola-SM56-V92QC-extDILlaserbeam.png)
The extended DIL is also used on the quick connect with the high latency, but the line probing phase was skipped. I suspect there may be different levels of quick connect, but achieving the fastest quick connect, especially under VoIP conditions where the impairments are different to POTS, is rather difficult.
Conclusion
A lot of calls were made, and some ISPs were probably annoyed. Variations on the V.90/V.92 handshake were examined, with differences in V.8bis negotiation, guard tone, DIL, scrambled data and INFO sequence length shown. It seems that certain chipsets (e.g. Rockwell/Conexant) have a habit of not sending scrambled data during DIL, whereas some others do.
With this posting, I think I am ready to farewell V.90 and V.92, and I think I won’t be too sad when the last V.90/V.92 modem banks are turned off and unplugged from the network for good. I’ll always be able to hear the comforting high-speed sound, and remember the various chipsets who were part of making internet connectivity faster and more affordable to the world.
While I wasn’t able to test every variation of V.90/V.92 chipset, the DILs recorded cover every chipset I know of (as most vendors use the same DIL for their whole family of chipsets), possibly with the exception of the IC-Plus/Topic chipset which I haven’t seen for sale or encountered personally.
I hope this post is enjoyed by those who enjoyed my legacy pages, and I hope it goes some way to helping you find your dial-up modem sound.
Nice work. I had no idea the old dialup modem was so complicated.
Mark
I think you should do Trumpet Winsock next. This should include version 1.0, 2.0 (first version with PPP support), 2.1 (first timelocked version), 3.0 (an attempt at Win95 support), …. This should also include Trumpet vs OzEmail lawsuits, and http://thanksfortrumpetwinsock.com/
I wonder if VoIP can be used to simulate a digital modem answering V.90/V.92 connections.
In theory, you can implement a digital modem that way, namely that your answering modem has its samples encapsulated into RTP instead of as digital (ISDN/DS*) signals. In fact, if you have a digital answer bank, and you connect it to a ISDN/DS* card of some sort that’s Asterisk capable, it may well be possible to have your own digital modem bank.
Unfortunately, as the V.90/V.92 standard is quite complex, especially in regards to training and echo cancellation, that even though you have “soft” V.90/V.92 originating modems (all those nasty PCI cards), there isn’t any VoIP-native software that will do such standards or even V.34 for that matter. V.17 (14.4k fax) does have several VoIP-native alternatives, namely t38modem and Digium Fax for Asterisk to name a few, which leverages both T.38 and “regular” audio passthrough methods. Unfortunately, because of a lack of market, I suspect a VoIP V.90/V.92 answer modem will never eventuate – also because VoIP is horrid at transporting such signals for long periods/over longer internet paths.
– Gough
This is so cool 🙂 But I cannot find the sound that I distinctly remember. My memory starts out like the contextant, and then instead of “white noise” there are more rapidly changing tones. I suspect that you recorded links at the max negotiable speed, and my memories are of hardware that is capable of faster speed, but negotiating to a lower speed? Anyways, still pretty cool.
Excellent resource! I’m building a hobbyist project which involves mimicking a modem connection. These sounds will really add authenticity. Thank you!
This is really awesome. I would love to see this done for X2 and K56flex, but finding a compatible termination point would be a real challenge. Same for Telebit PEP.
And v.32terbo! 🙂 That was quite a cool sound. I remember calling certain BBSes just to hear the connect sequence.
This is great! Hearing the modem noises with the outgoing/incoming channels separated into their own stereo channels puts a whole new dimension on things.
I remember the computer I used as a kid (a Toshiba laptop) made a noise like a machine gun going off during the DIL sequence, and I’ve been looking for it ever since. It’s not on here but listening to all the variations are very interesting.
What’s the one that made the sonar sound at the end?
Usually Texas Instrument based chipset modems did that
https://archive.goughlui.com/wp-content/uploads/2016/05/USR-Sportster-bong-bong.wav
I have a cisco spa122 ATA. I am unable to dial anything that starts with 019. I get a busy signal immediately. Any fix?
Does it give a busy tone mid-dialling? If so, could be dial-plan. Perhaps change it to (xxx.) which means 3 or more digits for a number.
Lots of VoIP providers do not terminate calls to 01xxxxxxxx at all, so you could well be getting a busy because your VSP is refusing to terminate to those numbers. Also check if the number is active – many older ISPs using Telstra’s modem banks have been turned off and their numbers are no longer active.
– Gough
im using the active dialup numbers. i can hear the dialup tone on mobile but the ata gives a busy signal once i enter 019
Then the number is active, but your ATA dial plan may not be allowing the number through. For 10 digits, you could replace your dial plan with (xxxxxxxxxx) which will accept 10 numbers only then put out the SIP INVITE request, or as I suggested, something like (x.) or (xxx.) if you can dial really quickly (like a modem does).
Best to have a Wireshark trace of the data going into the ATA as well, because your VSP may not be terminating the number correctly and giving you a reply of 4xx or 5xx.
– Gough
ill try that when i go home this evning.
Got another question relating to dial-up, to create a 33.6k DIY dial-in connection, that is as easy as connecting 2 modems together with line volatge and a way to ring one of them. but to make a 56k diy dial-in server, digital modems are required. i found a cisco router and the digital modem that attches to the router. it outputs to T1 line. problem is what happens next? were does the T1 line go and what equipment do i need to convert the t1 to analogue?
Your digital modem expects to be plugged into a digital line, so that’s what you’ll need. Perhaps consider plugging the T1 line into a T1 line interface on an Asterisk server and then accepting SIP connections from ATAs as a way of connecting analog FXS lines to it, although not ideal because there will be a fair amount of jitter buffering and packetization delays involved.
Perhaps you might need to buy some more equipment – maybe something like a second interface on the asterisk server that produces an FXS interface so you can basically route the call directly through the PBX or perhaps another interface that you might have the equipment to convert to an FXS interface – e.g. perhaps ISDN/BRI although I’ve never tried.
Good luck with your endeavours.
– Gough
ive tried the the various dial plans. i am using the (x.) as it works the best but this time, i dont get busy signal anymore, i get a voice sayng i dialed the wrong number.
Check with your VSP about the number format they expect – perhaps they need a full IDD+Country+Area+Number for out of area calling. However, I suspect they just can’t terminate calls to those numbers.
I’ve not used a single VoIP provider that can call 0198xxxxxx numbers at all, some of them return busy, unavailable, etc. This is one reason why I was very concerned about the loss of access to digital modems for these kinds of experiments. This is why you’ll have to find a non-01-virtual-area-code number if you’d like to hear your own V.90/92 handshake. There are not many remaining.
Otherwise, dialling overseas is a possibility but the likelihood of a V.90 handshake is even lower in part due to latency/packet loss but also due to the potential for a codec mismatch (i.e. USA uses G.711u, rest of world uses G.711a “in general”).
– Gough
Cant get the 01xx… numbers to work so ill just pass by. The 56K dial-in server i am planing to make is going to be used in a private system, in other words, the dial-in server goes straight to a computer and not to VOIP or landline, exactly like connecting 2 modems together for PPP conection. Ill use the ATA to ring the server. I currently dont have the parts to make the 56k dial-in server but when i figure out what items i need, ill order them. ive done alot of research but despite being new into this i kind of have an idea on how this might work. the connection starts from the router with the digi modem. it sends the signal out using T2. A second router takes the T1 and interfaces it to a ISDN/BRI network module card, producing the FXS signal. is that right? i probaly got something very wrong as i have no experience with this equipment.
To be honest, you’ll need to consult with an expert as frankly, while I have some idea of how it might look, I’ve never had the chance to own or play with the equipment. But basically you have a digital modem with a digital line – you need to interface an analog line to “eventually” for the client modem. How you make the transition is really up to you – it could be via an Asterisk PBX machine you set up with a T1 interface card on one end, and an FXS capable card on the other, bridging the calls together. Or you could possibly have a different interface, say ISDN-BRI and use some external equipment that takes ISDN and creates an FXS port or two out of it. Telecomms gear can be configured in a bewildering array of topologies – you’ll need to see what is available to you and what you really want.
I mean, it is possible to interface the analog modem to the FXS port of a consumer grade ATA and have it go over SIP to Asterisk with a T1 card to the digital modem – but I can’t guarantee this would work too well especially for longer connections due to the asynchronous nature of SIP. In fact, I’m not sure how accurate the sample clocks would be on “prosumer” gear such as the interfaces you might get for an Asterisk box. Desynchronization leads to burst errors and potential retrains/disconnections, so best to be avoided if at all possible.
While your dial-in server is for your own intranet – you’ll need to think about how you provide the inbound phone trunks to this digital modem bank. That’s probably where you might get stuck in some ways as the world is very much VoIP now unless you can get an T1/ISDN/etc digital trunk line from your Telco.
– Gough
ive been doing alot more research into making my own 56K dial-in server. I found 4 seperate cisco parts that can be asembled together to make the server and it is the cisco router, ISDN BRI interface card, digital modem card and the ethernet card. when asembled and programed, this allows a client to connect directly to the router using an analogue connection with real 56K v.92 speeds. i said in the past that i found a router with a digital modem that outputs T1. ive passed by this innitial config and the recent configuration eliminates the T1 interface and makes it ALOT easier to set up the server. i found the parts for very cheap, but i am in the process of saving up to get this amazing equipment.
Well, if you’re thinking what I’m thinking, then perhaps something like a Cisco 36xx/38xx with a digital modem module and an analog FXS module? Not being familiar with the gear, while I would like to build one of my own, I don’t think I can justify the investment as yet.
– Gough
ive sold a few items in ebay and collected $500 for getting the cisco equipment. ive been reading varius pages and mostly, a web guide on how to set up dial in with the folowing equipments, ive ordred a cisco 3640 router, NM-30DM digi modem, an E1/ISDN module, ethernet module and the part ive been trying to find for a long time, an access unit that converts the E1 ISDN interface comming out of the cisco router to 4 FXS interfaces. all equals to $364.35. pretty expensive but the most expensive part is the E1-FXS interface as it is SO EXPENSIVE but i managed to get myself a very good deal. once it arrives and configured, ill be my own V.92 provider (at least V.90 if not V.92)
Interesting, because I recently ended up buying similar equipment to try and do a similar thing but spending a lot less. I’m not sure it will work, but I wanted to give it a try with a Cisco 3825, NM-30DM, VWIC-2MFT-E1 and VIC-4FXS/DID (backed by a PVDM2-64) all in the same box. My plan was to use a crossover E1 line, with one port doing network side emulation and the other side being subscriber side, so calls would be accepted through the VIC-4FXS, passed out one E1 port, back in on the other and answered by the NM-30DM in the same chassis, routed to internet via the GbE port. I also have a second VWIC-2MFT-E1 just in case it doesn’t allow different operational modes on a per-port, or if looping back is not an option, I might use the card in a second Cisco 3640.
So far, I’ve spent about US$135 on my set of gear, thanks to best-offer pricing being accepted. The MICA modems are probably not my favourite, but it’s better than nothing – they don’t support PCM Upstream feature of V.92, which was something I’ve never actually been able to use in practice, but should still be able to do V.92/V.44 if the Portware version is correct.
– Gough
got your equipment and configured it? i got mine and the cisco router’s version was too old for the modem. i tried updating it and i ended up wiping the flash by accident. i now have a big 3640 just taking alot of space doing nothing. ill try to find a fix. the best part i bought is the RAD FCD-IP/E1/U/FXS interface. very hard to find and expensive. this box interfaces E1 to FXS and was the mox expensive part i bought. i think the router was the cheapest, $35ish or something like that. what drove me insane is the upgrading of the IOS for my router, the cisco downloads page does not have any downloads for 3640 and i had to search the entire internet. i found one but i never got it to install and after trying and reading other pages and lots of youtube vidoes, i think i deleted the flash by mistake and ruined everything. ill just work with my 2650XM with an NM-16AM module until i get everything fixed. the nm-16am is analog and it tops 33.6K. better than nothing but still, i would love V.92.
Sadly, still waiting on the postal service to bring me all of the bits. Living in Australia can mean 30-45 days wait for delivery of items from overseas … then I need to find the time to play with it. Right now I’m totally hammered with three RoadTest product reviews going simultaneously, so time is very much short. But I did pick up a few more VIC-4DID/FXS cards for cheap in the hope they’d be handy. I’m sure the flash can be recovered, although as you mentioned, a lot of the documentation and downloads for “out of support” products have been removed, so you’re best looking for third party mirror sites.
– Gough
what number have you been using for the dial up connections?
ive been trying my luck to restore the flash of the 3640 but because i cant find the IOS and there are lots of conflicting information about this unit, ill sell this unit with the 2600 and the 2600XM router to get some money to order a cisco 3825 router later on. any updates on the progress of your dial-in server? in my dial-in journey, i started off using an NM-16-AM-v2 and later the WIC-1AM module with the 2600xm router. the NM-16AM had compatibility issues with the router but the WIC-1AM works, it tops at 33.6K but i get no internet connection on the client side. i was not sure what was wrong so i passed by and after realising shortly that a digital modem is required for anything above 33.6K, i did alot of research and later ordered the equiment required for a V.92 server but then obviously hit a brick wall when it comes to the operation of the router. i decided to give up the routers i currently have and think about a router that would be more compatible with my digital modem and the E1 network module. oversease postage does indeed take forever. i live in sydney as well and i know the feeling of waiting for an item to come from oversease. it took a few days for my cisco 3640 unit and the interface cards to arrive as it was located eather in sydney or melbourne but the E1 FXS interface took almost forever to come. the 3825 router i am planing to get is in melbourne as i dont want to wait for an oversease item. hopefully, more luck with the 3825 router.
Hmm. I’m still waiting on the final part (a pair of Cisco Multiflex E1 WAN cards) and some time to work on it.
Perhaps you can download a suitable image from https://www.careercert.info/new-cisco-ios-version-124-collection/ – I note the one listed as c3640-ik9o3s-mz.124-25c.bin may well be the latest available for the 3640, so maybe you can get it running if you save it to the CF card (assuming it is still formatted in its original format).
– Gough
ive just got a good deal on ebay recently to go with my dial-in server. its an Excelltel PABX module, this allows me to dial in to the server from the client by dialing 601, 602 etc. currently waiting for the item to arrive. the 3640 router, it has so many problems, firstly it uses pcmcia cards for flash and it only supports up to 20MB. cant find any IOS that is under that amount. second is it is HORRIBLE to try do anything to flash the router, i mean i experienced problems like never before. third is it costs the price of a 3825 to buy the pcmcia card and is so difficult to find the correct model so im saving up for the 3825 router instead. another reason why very old equipment are out of support in favour of new modern and much MUCH more flexible equipment. anyways, the PABX, i can also use it as a telephone and fax innercom, which would be fun. it has 3 pstn lines and 8 extentions. i am planing to connect the NBN phone line to the box and connect 4 of the connections to my E1-FXS interface of my dial-in server and the rest to telephones/fax/computers. so when i dial an extention number the dial in server is connected to, it rings the server and starts the connection. ill configure the pabx so if anyone calls my home number, it would not end up calling my server without my permission and instead, routes the call to my main phone. i can allow the outside to call my server for fun. not sure how voip impacts the connection but should be able to make a successful V.92 connection if everything is right. idealy, an ISDN line is needed but i am not going to become an ISP so no need for that.
just found a good deal in ebay and picked up a 3825 router. but, i just realised after issues configuring the system that my E1 ISDN PRI module is not compatible with my router. the modem works but cant configure the IDSN configuration becaus of this. have to spend $40 on a compatibe unit. starting to excceed my budget so ill see what i can do. i always wondered what 56K server equipment was used by ISP’s. i always want to get the ISP’S full featured equipment but thats not common and is extreamly expensive if i can find anything. im thinking about an entirely diffrent server, a portmaser 3 but i just discovered this equipment so im not sure. not alot of information other than the configuration and lots of listings on ebay from the US. seems promising as it is a remote access server with digital modems.
The ISPs used modem banks, typically the Cisco AS5200, AS5300, AS5400 and AS5800. They either had Channelized T1s with in band signalling or T1 or E1 BRI connections from the phone company.
in reply to Phillip Remaker, thank you so much for providing me the model of the next remote access server i have ordered, the cisco AS5300. i found one at a great deal complete with MICA modules. when i get it, it should be mostly configured but probaly adjusting the ip addreses is all i need to be done. the system is WAY overkill but i always loved getting a hand of real enterprise grade equipment. ill see how i progress when the item arrives.
Glad to help. Feel free to email me at my last name at gmail.com if you need any specific help.
i got my cisco as5300 recently, all configured and working but… well… um… for an ISDN remote access server to work, you need an actual ISDN service for the signaling. and from there, ive just hit a solid metal wall. ISDN simulators are EXTREAMLY expensive, arround $1800 to $3000 for one on one website i found. now, i am starting to wonder how to interface the ISDN to FXS to my modem. anyways, you having the same problem with your setup or is it working better than mine?
Unfortunately, it doesn’t look like I’ll have much or if any time in the foreseeable future to play around with what I already have. I haven’t found success yet – I’m not sure exactly why but while I do have my E1 network emulation and E1 client connection seemingly working, calls aren’t being picked up by the modem pool on the inbound perhaps due to incorrect bearer-cap setting or something to do with the line numbering. Regardless, I’m shelving the project while I get some other more important things done – but what you’ve seen is what I’ve learned a while back – ISDN network-side emulation isn’t common nor cheap. That’s why I’ve tried to stick with things that have T1/E1 interfaces so far.
– Gough
You should be able to set up up as Channelized T1 instead of ISDN. Unless you only have E1 interfaces, which don’t have an equivalent channelized mode.
You should be able to do network side emulation with Cisco as well… https://community.cisco.com/t5/collaboration-voice-and-video/how-to-configure-network-side-isdn-pri-signaling-for-pbx-in-a/ta-p/3133212
in reply to gough, probaly the reason calls are not being picked by the modem pool is because a network module E1/T1 card is required in conjuction with the modem bank (NM-1CE1T1-PRI or somthing like that.) probaly might fix your problems. i read from someware that interfacing to to digital modems does not work using WIC modules, only NM modules.
ill try E1 instead of ISDN as my access server can do E1. ill might do the same setup as yours when it comes to the E1 simulation and the FXS stuff. i am still keeping a very close eye on this item https://www.vconsole.com/product/93 , very expensive but the best way for interfacing the access server over E1/T1/ISDN PRI TO FXS. mabye i might find it on ebay at a much lower price?
i would like to make the E1 emulation system you have, just to find out if it works in my setup. i have a 3825 router, a 1 port VWIC E1 card and i still have to get a PVDM2-64 and the FXS card. can you email me the config you have? so how im planing to make my system work is the AS5300’s E1 connection goes to the E1 card via crossover cable on the emulator (3825 router) and it then interfaces it to FXS. is that similar to your setup? with this setup, do you connect the modem directly to the FXS ports and dial a number set on the router or do you need another device like a PABX?
after more searching arround, you can use ISDN BRI network module on your 3825 router. you need to simulate the BRI signaling and you can find isdn BRI simulators on ebay, although it comes and goes from time to time. what happens is the 3825 with the modems connect via BRI to the simulator, then the output from the simulator goes back to the 3825 but to a WIC BRI card then the router does the job of the BRI-FXS interfacing. MUCH better luck finding BRI equipment because PRI is just super expensive, ive heard it costs thousands of dolars a month for a PRI service while BRI cost a million times cheaper.
im shelving my AS5300 as it is only PRI and im experement with my 3825 router.
Sorry for the delay in replying – I’ve just been so absolutely busy, I haven’t even had the time to respond to comments. Indeed, it seems that if you want to go ISDN, BRI is probably the easier choice but the network side emulation has always been an issue. I really don’t yet have the time to play with mine, but I suspect you might be right in regarding needing a voice network module to handle incoming E1/T1 to the digital modems even though WVIC would imply voice support on the 3825 chassis ports themselves. I’ll probably get around to it one day … hopefully soon, but unfortunately, there are many more important things to worry about right now so it will have to rest on the backburner.
– Gough
it has been a very long time. ive successfully made a system that enables me to make my own 56K V.92 dial-in server. VOIP based but more info later. my RAS AS5300 is plugged using E1 PRI to an amazing product, a Digium G100 T1/E1/PRI to SIP/VoIP Gateway i bought for only $10!!! i assigned a 1800 number on the gateway and i call it using my cisco SPA-122 ATA. but some days later, my AS5300 suffered a PSU failure because of a sudden power surge. luckly, all of my other electronics are safe, including the gateway. i am going to use my cisco 3825 router as the RAS. once i get it working, ill enable V.92 and mabye you can countinue to test your modems?
my server works very good but being it is VOIP, it does become problematic over time. ive only being working on it for an hour before shelfing it for studys. becuase of the failure of my AS5300, i am going to use my 3825 but still waiting for the PRI network module to arrive.
in other talks, the last and only 1800 based dialup number remaining in australia is used by optus prepaid. i use it for fun but just a few weeks ago, i managed a V.92 negotiation! i even have some audio and videos too. i also recorded some very intresting fails that occured during the negotiation, like the failure of the DIL tone, corrupted random noise when the PCM training data comes from the server to some other wierd stuff. i did managed to catch that until it was reverted back to V.90. what a good catch
Interesting to hear of your progress. Unfortunately, I’ve been too busy with other more important things to have the time to play around with it. Sad to hear of the failure of the PSU in the AS5300 – perhaps you can buy and install another module?
Yes, I have mentioned the fact regarding the 1800 number in other articles on this site – I didn’t want to mention it here as I didn’t want it to be abused to death. Remember that 1800 numbers result in charges to the carrier – free for us, but not to them, so I try not to make unnecessary calls. Seeing V.92 suggests they may have some modem cards with different firmware on them – in the old days, the Microsoft ISP Referral 1800 number was likely served out of Telstra equipment and was a consistent number to get V.92 connects (with occasional QC, but no MoH ability). I’ve had certain issues in the past where we’ve had lines which seemed to be answered as a digital call resulting in constant loud noise rather than the expected modem tone negotiation.
– Gough
Any updates on your 56K dial-in server? I am wanting to set one up myself and would be interested in hearing more about what all you did to get it properly set up and working.
Hi Jeremy,
Unfortunately not – I’ve got way too many things in the way that are more important, so I haven’t had any time to devote to that. Maybe I’ll have the time to get back to it someday – but at this stage it seems doubtful. I probably will need to get some additional hardware as well as things didn’t quite work out the way I had planned with the WVIC slots on the rear of the 3825 as I’m not getting the modem pool answering a loop-back call on the E1 – part of the reason may be due to hardware restrictions so I probably need an E1 voice NM to go into it, and I may also need more PVDM channels too as the E1 has more channels than the T1 and adding the FXS/FXO ports I have in the unit, I’ve saturated the PVDM channels I already have. I have configured it to try and work as a fractional E1 – but I suspect that type of configuration only makes things more likely to “break”.
– Gough
Its been a few years since the post regarding making a 56k server using Cisco parts, i recently had a go at making one using a Cisco 3825 and a few modules, ive sucessfully been able to make a 56k V.92 dial-in server, in my YT video: https://youtu.be/DP1eDYleOAQ
Seeing your recent comment that you were able to setup a server with the cisco 3825. I have the same equipment that I have been trying to get setup, however have ran into some issues finding a newer version of IOS. Mine is on 12.4 and can’t find an image of it anywhere. Do you happen to have anything to point me to?
https://drive.google.com/file/d/1Q3eUZ_zuBy9BCyvxB0II_Q5QH9gVuPD0/view?usp=sharing
The sound of 300 baud is wrong, this sound would be telling me that my amiga was calling and not getting through, the sound of 300 when connected is more motor boaty you could probably connect two modems together through a simulated phone line, I’ve seen such basic circuits that don’t seem to need many parts, the other thing is the old commander systems or some such, they’re switchboards for pots lines for small n large businesses, back in the day.
Anyhow, the 300 sound is saying it is trying to connect but cannot. memory lane. Actually, the sounds from later modems trying 300 or 1200 and so on are probably different. As modems progressed they started trying to connect first at high speed, then at lower speeds until finding one that worked. So 300’s would just get to it without asking 9600 ?? 2400 ?? what about 1200, surely you can do 1200 ? 300 ! you got to be kidding me. They’d go on like that in beeps and buzzes. Ah those were the days. People were nice back then. Trolling hadn’t been invented yet, you needed to be educated or gifted to use computer communications. Now, well, its been declared a warzone by the usa along with their announcement of a space force. sheesh. The pentagon needs a sign on the wall saying “During work hours please refrain from smoking cannabis or munching on meth-amphetamines, your country thanks you.
Once thing you didn’t mention is the pre-V.90 competing standards. US Robotics pushed their X2 technology, and Rockwell/Motorola/Lucent pushed K56 (aka K56plus, K56flex) technologies. Those both sounded different, but it would be hard to reproduce those since you would need to find pre-standard modems supporting each.
Oh, but I don’t feel the need to mention them here when they both have featured in separate articles on this site:
– https://goughlui.com/2018/06/10/project-record-a-us-robotics-x2-dial-up-modem-connection/
– https://goughlui.com/2018/06/10/project-record-a-k56flex-dial-up-modem-connection/
– Gough
Wow… this was definitely an excellent and I can see that you put in a huge amount of effort into dissecting the data handshakes. While I get you may have gotten burned out after doing an incredible amount of work, have you considered PSTN cartography (aka Wardialing on a global scale?)
I just mention it because we at telephreak.org are sort of into things like that. 🙂
geeze…
“*excellent read” I meant to say.
Thanks for the comment – I can’t say I’ve been into that kind of thing, although perhaps for preservation sake, it’s an opportune time to capture the last of some systems that may still remain. While SIP gateways can make such things easier to achieve, issues around legality and fair-use mean that I probably wouldn’t be partaking in those kinds of activity. Some voice service providers won’t terminate calls to certain blocks of numbers either, which is a bit of an impediment.
That being said, I do enjoy hearing many phone tapes from the mechanical switch days – Evan Doorbell is pretty much a hero in preserving and presenting the content in an engaging and interesting way.
– Gough
Indeed. If we ultimately keep progressing to decommission copper-AD/DA technology for the packetized facsimile, none of those switches globally will be of much use. I do believe, however that there are a lot of parts of the world that haven’t upgraded extensively beyond the patched systems built throughout the early/mid-1900’s. Last mile connectivity will be a problem for the next 75 years even with satellite constellations like StarLink. There’s only so much wireless spectrum. 🙂
Have you checked out C*Net? Very cool distributed network for the researchers and hobbyists. https://www.ckts.info/
I have recorded a TOPIC based MODEM’s DIL sequence. It is almost exactly same as NetComm Conexant based Modem.
Try looking at these samples through a Goniometer…makes a great screensaver if you can capture it.