Build your own Dial-up ISP with a Raspberry Pi
jeffgeerling.com
jeffgeerling.com
The main catch is that they have a 50-pin Centronics style connector on them which you will have to break out somehow to your RJ11s. Also, they are big (1U rack) and have fans.
I've got a few of these and have been meaning to set them up with a bunch of modems and a bunch of computers, but haven't gotten to it yet. Modems do seem to work in the limited testing I've done. They do (as expected) work great with telephones, including pulse dialing.
This is just another lost art (traditional phones are either dead or are instead IP) that I once learned a fair bit about:
The name varies regionally (I've heard them called Centronics, cinch, and CHAMP; though around here, we call them Amphenols). The Easy Method is the same regardless of name: It centers around a split (aka "50 pair") 66 punch block[1] that is mounted to a wall, or to a wall-like object.
Buy a pre-terminated 25-pair cable with the right connector on at least one end, and punch that down in order[2] on one side of the 66 block. That connects the system to the punch block. Importantly, those wires never get touched again.
Phones (or more precisely, wires for jacks for phones) connect to the other side of the 66 block. Those wires also never get touched again.
The two things (phones, systems) are connected/disconnected with bridge clips that combine the two halves of the block (which only allows 1:1 ordering, but that's often just fine).
Alternatively, a "we fancy!" variation uses single-pair cross-connect wire so that arbitrary phones can quickly be connected to arbitrary system ports -- maybe on completely separate blocks.
After that, plug in the Amphenol. Plug in the phones. Have fun talking to yourself.
(Or, at least: That's an easy way for small stuff. Bigger stuff (hundreds or thousands of pairs) eventually really wants better organization, but punch blocks are still normally the order of the day there, too.)
I know we ripped out similar, a plastic panel/wall mount version, at an old job when we went VoIP. The Centronics came out of the PBX. Probably find on eBay or surplus. Maybe talk to IT and they have one hanging around in a junk pile.
> The name varies regionally
Micro Ribbon connector https://en.wikipedia.org/wiki/Micro_ribbon_connector
Or a person can buy a patch panel pre-assembled with an Amphenol connector, and just plug in a 25-pair cable between that and their gear. Here's one from Leviton: https://leviton.com/products/49012-j24
Or, there's unholy creations like this octopus breakout cable, which can be used to connect existing patch panels/structured cable plants into Amphenol world: https://www.sandman.com/products/cbl3c-6-foot-qwik-25x2-cabl...
And those kinds of things are great for rapid deployment, but we're not trying to do that -- are we? We're just goofing around with old telco stuff for the lulz.
The most tinkering-friendly option is 66 block (wherein: the structure is whatever we want it to be today), I think. Punch down tools are cheap (including those that have interchangeable blades for also doing tidy work of 110 keystone jacks). It only takes a few minutes to land all 25 pairs, and those pairs can do anything a person wants them to do.
Meanwhile, 66 blocks themselves: They're dandy things. I've used them in the field to build simple circuits: The resistor or the capacitor doesn't care that it is hanging off of a punch down block instead of soldered to a PCB. It works, and it's wall-mountable for permanence.
But yeah, there's certainly options. I've got good familiarity with 66 blocks and their ability to quickly (and rather universally) hack stuff together, so that's what I tend towards using.
> Micro Ribbon connector https://en.wikipedia.org/wiki/Micro_ribbon_connector
It's always important to know the specific and most-correct nomenclature, but it's equally important to use terms that others easily understand. :)
Like, the 4-pin Molex connectors in common use for things like PC optical drives (where those still exist). You probably know exactly what I'm referring to, and can picture one in your head whenever someone mentions a "Molex connector" in the context of a PC.
But those aren't from Molex -- they're instead from Amphenol's Mate-n-Lok line. Molex sells compatible-enough versions (as do countless other manufactures), but Molex had nothing to do with the design or introduction of that part.
Meanwhile: The square 4/6/8/20/24-pin jobbies that connect to things like video cards and motherboards, and that seemingly everyone calls ATX connectors? Those actually are Molex parts (from their Mini-Fit Jr line), but people would be confused AF if you called them Molex connectors.
So if we're doing it right in casual discourse, we use the terms that people understand -- even if they're not necessarily maximally-correct.
I've never witnessed the term "micro ribbon connector" used in face-to-face dealings involving telco stuff.
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Up next: The male 1/4" audio connector. Is it a headphone plug? A guitar plug? TR? TRS? A phone plug? A jack plug? "Like an aux cable but bigger?" Yes, any of those terms work. The best term depends on the audience.
The connector originates in the forgotten world of plug-and-socket telephone switchboards, so of all of those options "phone plug" probably gets the history most-correct (and that's also what Radio Shack labeled them as). But that specific terminology is pretty archaic at this point.
It's so archaic that if I asked a sane and rational person for a cable with "phone plug" on it these days, they might go looking for something with 6P4C, 8P8C, USB C, or (maybe!) a TRS -- depending on their age and/or upbringing.
From what I understand of telecom of that era. You want to effectively keep as much of the signal digital as possible. With (ideally) the only "analog" part remaining being the link between the customer modem and the PBX.
The VG224 being (effectively) 24 ATA's in a trenchcoat seems to meet that requirement. Though once installed you'd need to connect it to a PBX such as Asterisk. Then, as I understand it, "trunk" that as a T1 line into something that can digitally handle modem calls such as a Cisco AS5300.
They do have enterprise accounts where I presume you'd be able to subscribe to 24 phone lines, but that would not be cheap! Whether they'd even allow you to bring 24 phone lines into a residential house is another question. They might not even have trunk capacity to offer you that many lines at your residence, so then you'd need to lease office space so they could bring in a T1 line.
I'm assuming these numbers are flagged as VOIP (which limits their use as a lot of apps/sites/companies hate VOIP numbers), however the discover is interesting. I thought home phones were dead and buried.
Yes, it's VOIP. You might get a "real" number with appropriate area code that might route through the real POTS network. Depends on locale and ISP
https://fosdem.org/2026/schedule/event/UJKT3L-dial-up-howto/
Would be neat to read email with an old POP client, or chat over the original AIM software (perhaps patched to use a server on the LAN)
However, to be frank, it'd make more sense to do PPP over null modem with a straight serial connection.
But then again, based on Pi pricing today, the $120 telco simulator goes nicely with a $300 Pi 5.
You can also use an old VoIP ATA from Linksys/Cisco as a cheap line simulator. Like a fully analog TLS the ports can call each other. They can be a PITA to configure right but they're cheap and work well enough.
I've used all three methods, the TLS is the easiest. An ATA can be useful if you've got more than one and your dial-in server is in a different room from the client you're playing with. An ATA can also be set to "call" another device. So your office ATA can call the basement ATA (with your Linux server) as an example.
Just issue ATX0D on one modem and ATA on the other. Bingo bango: One modem thinks it's initiating a call (without concern about the lack of dialtone), and the other thinks it is answering a call.
But yeah, simulators are fun. A person I used to call "boss" used one with a dry pair of copper that ran all the way across town for his internet connection for a couple of years.
(His shop had space that was used by a local dialup ISP for a POP. In exchange for the space and the electricity, his shop got free internet over a T1 in the days before we had DSL or DOCSIS. It was a great trade for both parties and I felt giddy downloading things at work at >1.5 Mbps instead of ~0.0336 Mbps.
In an effort to save some money on a dedicated phone line and ISP bill at home, he ordered a cheap circuit from the phone company that they billed as an "alarm circuit" -- it was about $20 per month.
One modem was his at house behaving mostly-normally along with the simulator, and another was at the shop connected to our all-singing, all-dancing 486DX4 Linux box. It was stable and cheap and somewhat ridiculous.)