Yup. I worked on the "Rapport" series of switches at Bell Canada. It was DS1 (Digital Signal 1) out one end and a rack full of Zyxel modems on the other side. The idea was RBOCs (Regional Bell Operating Companies) would put these in their CO (Central Office) and terminate 56k modem signals over the analog "last mile" loop to the customer premises and then do Frame Relay over the phone company's data lines to your ISP.
I know Southwest Bell bought a number of them and stuffed them in a closet north of downtown Dallas. During the install I remember having to explain what Ethernet was to their techs. They were EXCELLENT at phone standards, but had decided the data world was threatening and were determined to never learn anything about it.
I know that between around '93 and '97 if you dialed AOL from D/FW there was a good chance your call would be terminated somewhere within a mile or two of your house and the bits flowing between your Compaq Presario and AOL would be sent digitally from the local CO to AOL's data center in Sterling, VA.
This line of business was (of course) destroyed by consumer DSL and cable modems, but for about 5 years it was fairly popular with the phone companies. ISDN at the time was a bit pricey for most households and a modem is a one-off purchase. Most people I knew using things like AOL or CompuServe were using a hand-me-down 36k modem on a crappy 33MHz 486sx running DOS / Win3.1 / Win95 and were fairly cost-sensitive.
> DS1 (Digital Signal 1) out one end and a rack full of Zyxel modems on the other side
Why use real physical modems when you already have subscribers signals converted to convenient digital form in DS1 bundle? Wouldnt it make more sense to put a box with one fat DSP doing 24 modems all in bulk inside a box with DS1 and Ethernet sockets at the ISP location instead?
Revealing my ignorance here, but was (is?) there a telephone equivalent of anycast such that, say, the 1-800-... Or 1-900... numbers would be routed differently based on location? My basic knowledge of phone systems suggests it would at least be possible.
Isn't DSL basically the same thing? If you live in a jurisdiction with unbundled local loops (which I suspect you do not), your phone company terminates your DSL at their nearest "office" (often a roadside equipment cabinet nowadays) and then does Metro Ethernet over the phone company's data lines to your ISP.
If you don't live in that jurisdiction, it's the same but your ISP and your phone company are the same company.
>I know that between around '93 and '97 if you dialed AOL from D/FW there was a good chance your call would be terminated somewhere within a mile or two of your house and the bits flowing between your Compaq Presario and AOL would be sent digitally from the local CO to AOL's data center in Sterling, VA.
Around the end of the dialup era, I noticed a bunch of similar low cost dialup services all used the same phone numbers, is this part of the reason, or were they all just reselling the same internet access or something?
To be clear, this was well known at the time. It was advertised that 56k was for download only and required an ISP that supported it. For those living in rural areas, there often weren’t any local options (long distance was certainly not free in those days). But for those who could get it, it was definitely a big improvement.
I'm still mad that they high-quality voice audio possible through ISDN didn't become ubiquitous. It's ridiculous to hear the clipped frequency range of a plain old telephone line during radio interviews in 2025.
That 128Kbps on ISDN was the like the gold standard back then! I knew some sysadmins who had that installed to their homes so they could be available at any time. All paid for by the company they worked for.
Indeed ISDN was amazing for its time but Ma Bell and her successor ILECs were way too proud of it so in the end it went nowhere and never made them all that much money.
If they had gotten out of their own way when the internet came around they could have charged a small monthly fee to upgrade to a "digital phone line". Lots of people would have switched.
Both our ISP and the phone company charged for every BRI data "call" placed and for minutes connected rather than a flat rate on a business-class ISDN line. I discovered IBM AIX's web browser package contained a telemetry background process that dialed home to Big Blue every 2 hours, causing our Cisco 1604 router to dial-on-demand even when no one was in the office. A simple deny IP ACL fixed that problem. There was no opt-out and no mention of it, and it never became a story that it should've been.
As a kid, we didn't have ISDN, but we did have a second phone line dedicated to the modem.
My dad ran a BBS from like 1992 to 1995, which started falling out of favor, especially as the users were getting more busy signals because the modem phone line was tied up with the internet connection.
TIL why upload on 56k modems were capped on 33.6k. I always wondered about that.
Super interesting stuff!
I also remember back in the day that my 56k modem would often only connect at like 48k or so, especially when it was raining. I guess living far out from the city made the connection more noisy?
Isn't it the opposite of the headline? Modems were hamstrung by digital phone lines you didn't know we had. One final trick allowed them to match, but not exceed, those digital lines.
To me it looks like the article is largely told from the perspective of ISPs connecting themselves between each other, and how the constant analog/digital conversions between carriers were causing problems sustaining the 56k data rate that the (analog) last mile was always capable of... and how converting their internal systems and backhauls to digital solved that issue.
The analog lines before digitalization were limited to 8kHz bandwidth. This is because to deliver a circuit between two points, the system generally figured out which bit of bandwidth wasn’t in use and frequency shifted the entire connection into that band.
Yeah kind of. The u-law sampling of audio to produce the 64kbit audio channels in ISDN isn’t good for encoding a signal created by a modem.
But if it was a direct copper pair end-to-end then attenuation and electrical other characteristics would have made it hard to achieve the higher speeds, this is the Shannon limits they mention.
I had made a small career on building Internet Service Providers in California, in the early days, and will never forget how liberating it was to carry my laptop to the Griffith Park observatory with a fully-charged Ricochet modem plugged in, communicating to my house down in Los Feliz, where another Ricochet modem gateway'ed me to the Internet via the house 56k line ..
It was truly astonishing to be up there, checking email.
A few, what seems very short, years later .. and now it is just normal.
I have to wonder if the cap (theoretical) on the copper wires was more because of the technology standards in play at the time. Surely the copper wires could have handled more if they did not have to carry voice communication (with the old tech specs of the time) any longer?
Ok. Searched around.
Here is an article that states old copper could have carried 1 gigabit.
The practical implementation of this (at the time) was ADSL, HDSL, IDSL, and SDSL. Those technologies all took one or two copper pairs, and terminated them on a DSLAM (or similar device in the case of HDSL) instead of on a telephone switch. For physical pairs connected to an analog voice port on a telephone switch, between the band pass filtering and DSO coding, you were never going to get more than 56kbps. The xDSLs could get between 144kbps to a several mbps in practice, depending on the variant and line conditions.
Keep in mind that at the time, LAN speeds over controlled twisted copper pairs over short distances (100m) were 100mbps - 1gbps.
If you've ever seen the physical condition of the telephone company's outside subscriber wiring (what they call "outside plant") -- and particularly the intermediate splices between central office and subscriber -- you would quickly disabuse yourself of the notion that you could transmit anything close to 1gbps over a twisted pair.
Those copper wires ran from your house to the local central office, the "last mile" of the connection. (which was sometimes 2-3 miles long)
A quick read of the linked article seems to indicate that it's BS, as it doesn't account for the real topology of the local loop. In particular, in older neighborhoods you had a bundle of pairs going down the street, and a new connection was made by patching in to a free pair, creating a "T" shaped circuit. When a house was disconnected, part of this "stub" might have been left attached; over time a single pair might accumulate multiple disconnected stubs. The capacity of that copper circuit is far lower than a straight run.
In addition in many cases corrosion and water cause noise, further reducing bandwidth - I can remember having noise so bad on rainy days that I had to call and get them to fix it. (I assume they patched us onto a free pair and abandoned the noisy one)
Of course none of this is related to the end-to-end bandwidth of the old telephone system. Starting in the 50s a longer-distance phone call would get a single-side-band channel on a microwave link, with about 3KHz allocated. Later on calls got sampled at 8KHz with 8-bit mu-law (logarithmic) encoding, or A-law in Europe, and transmitted digitally.
Of course ancient telephone wiring can carry 1 Gbps. The real question you always, always, always, need to be asking yourself is:
Over what distance?
Make that distance short enough, as has happened with FTTN, or FTTC deployments in a whole heap of places, you're basically building a network that's, and I'll keep this very brief, subpar.
Since you mentioned a UK context there, Openreach rolled out an upgrade that kept the last mile of copper but now just about a decade later they're rolling out Full fibre. Whatever argument copper had, it went out the window near enough a decade ago.
Distance is the problem. The gauge is small so we can't throw a very strong signal down the wire. So you have repeaters on almost every span of any appreciable length.
The very first part of a dialup modem sound? Where it's playing a tone that reverses phase at regular intervals? That tone is actually designed to disable all the repeaters and echo cancelers that are in your switched circuit.
Also two parallel phone lines are prone to capacitive coupling. I had a case so bad once that one office could pick up the phone and nearly perfectly couple onto their neighbors line and hear all their conversations. It was a 50/50 which port on the PBX recognized the tones and started the call when either of them picked up to dial out.
it can carry more, the whole value proposition of dsl was a high speed link over existing cabling, I think the dial up limitation is what speed can you sneak over the existing speech focused analog signal processing equipment. where as the article explained by making that analog link as short as possible it could improve speeds quite a bit. dsl was what you could achieve over the same lines when you were not forced to constrain your signal to speech frequencies
I remember some ISPs allowing you to "shotgun" two 56k modems for double the speed!
Like some other commentors I also fondly remember ISDN. Overall I found it to be finicky. Sometimes one channel would just drop, even if a phone call wasn't coming in. And, in order to use a traditional analog phone with your ISDN line, you needed a special powered "TA" adapter or the phone wouldn't ring when a call came in.
Now I'm curious about how this worked in my city where we most definitely didn't have anything digital to our phone system at the time. As in, you had to use pulse dialing, and sometimes, rarely, your calls would glitch such that you would hear someone else talking over your call. Yet I remember consistently getting 40-something kbit over that.
I remember the day we got 56K from our ISP. Our modem was 56K (no idea what model, some internal WinModem), but the ISP was limited to 33.6K. Then one day, the connection screech sounded different, and I excitedly pointed this out. Several seconds later, it connected, and lo and behold, we had 66% faster downloads.
The fact that all of this worked continues to amaze me, but then, so do mobile phones. I understand at a high level how CDMA works, but it’s just so insane…
Around 2000, I saw a crew pulling new phone lines through the neighborhood because everybody was getting a second line and they were running out, but even after switching to the new copper, we were still stuck at 26400. 20+ years later, it looks like 25/5 ADSL is now available at that address, so the new copper wasn't a complete waste.
Yes these modems were almost-ISDN (minus the razor fast call setup). And required a full digital backend to work. They could only do 56k6 in one direction, to the user too. But they were made for internet access so that didn't really matter.
ISDN had much, much better latency than even 56k modems. Modems were around 150ms minimum. ISDN was often in the sub 20 ms range. This made a big difference for chatty protocols like HTTP, telnet, etc.
I remember my brothers friend in rural Portugal having one way satellite Internet back in the 90s to very early 00s - you used a standard dial up for the upstream, but with a satellite dish got much much faster downloads. Blew my mind that you could go out one way and receive another and still get a functioning (and fast) connection.
[+] [-] OhMeadhbh|1 year ago|reply
I know Southwest Bell bought a number of them and stuffed them in a closet north of downtown Dallas. During the install I remember having to explain what Ethernet was to their techs. They were EXCELLENT at phone standards, but had decided the data world was threatening and were determined to never learn anything about it.
I know that between around '93 and '97 if you dialed AOL from D/FW there was a good chance your call would be terminated somewhere within a mile or two of your house and the bits flowing between your Compaq Presario and AOL would be sent digitally from the local CO to AOL's data center in Sterling, VA.
This line of business was (of course) destroyed by consumer DSL and cable modems, but for about 5 years it was fairly popular with the phone companies. ISDN at the time was a bit pricey for most households and a modem is a one-off purchase. Most people I knew using things like AOL or CompuServe were using a hand-me-down 36k modem on a crappy 33MHz 486sx running DOS / Win3.1 / Win95 and were fairly cost-sensitive.
[+] [-] rasz|1 year ago|reply
Why use real physical modems when you already have subscribers signals converted to convenient digital form in DS1 bundle? Wouldnt it make more sense to put a box with one fat DSP doing 24 modems all in bulk inside a box with DS1 and Ethernet sockets at the ISP location instead?
[+] [-] plorg|1 year ago|reply
[+] [-] immibis|1 year ago|reply
If you don't live in that jurisdiction, it's the same but your ISP and your phone company are the same company.
Also you don't dial your ISP with a number.
[+] [-] ubercore|1 year ago|reply
[+] [-] Suppafly|1 year ago|reply
Around the end of the dialup era, I noticed a bunch of similar low cost dialup services all used the same phone numbers, is this part of the reason, or were they all just reselling the same internet access or something?
[+] [-] pimlottc|1 year ago|reply
[+] [-] sureIy|1 year ago|reply
[+] [-] xnx|1 year ago|reply
[+] [-] stuff4ben|1 year ago|reply
[+] [-] xenadu02|1 year ago|reply
If they had gotten out of their own way when the internet came around they could have charged a small monthly fee to upgrade to a "digital phone line". Lots of people would have switched.
[+] [-] cantrecallmypwd|1 year ago|reply
[+] [-] Sohcahtoa82|1 year ago|reply
My dad ran a BBS from like 1992 to 1995, which started falling out of favor, especially as the users were getting more busy signals because the modem phone line was tied up with the internet connection.
[+] [-] kreddor|1 year ago|reply
I also remember back in the day that my 56k modem would often only connect at like 48k or so, especially when it was raining. I guess living far out from the city made the connection more noisy?
[+] [-] immibis|1 year ago|reply
[+] [-] ranger_danger|1 year ago|reply
[+] [-] chipsa|1 year ago|reply
[+] [-] topranks|1 year ago|reply
But if it was a direct copper pair end-to-end then attenuation and electrical other characteristics would have made it hard to achieve the higher speeds, this is the Shannon limits they mention.
[+] [-] aa-jv|1 year ago|reply
It was truly astonishing to be up there, checking email.
A few, what seems very short, years later .. and now it is just normal.
[+] [-] hackthemack|1 year ago|reply
Ok. Searched around. Here is an article that states old copper could have carried 1 gigabit.
https://www.newscientist.com/article/2317040-ordinary-copper...
[+] [-] marcus0x62|1 year ago|reply
Keep in mind that at the time, LAN speeds over controlled twisted copper pairs over short distances (100m) were 100mbps - 1gbps.
If you've ever seen the physical condition of the telephone company's outside subscriber wiring (what they call "outside plant") -- and particularly the intermediate splices between central office and subscriber -- you would quickly disabuse yourself of the notion that you could transmit anything close to 1gbps over a twisted pair.
[+] [-] pjdesno|1 year ago|reply
A quick read of the linked article seems to indicate that it's BS, as it doesn't account for the real topology of the local loop. In particular, in older neighborhoods you had a bundle of pairs going down the street, and a new connection was made by patching in to a free pair, creating a "T" shaped circuit. When a house was disconnected, part of this "stub" might have been left attached; over time a single pair might accumulate multiple disconnected stubs. The capacity of that copper circuit is far lower than a straight run.
In addition in many cases corrosion and water cause noise, further reducing bandwidth - I can remember having noise so bad on rainy days that I had to call and get them to fix it. (I assume they patched us onto a free pair and abandoned the noisy one)
Of course none of this is related to the end-to-end bandwidth of the old telephone system. Starting in the 50s a longer-distance phone call would get a single-side-band channel on a microwave link, with about 3KHz allocated. Later on calls got sampled at 8KHz with 8-bit mu-law (logarithmic) encoding, or A-law in Europe, and transmitted digitally.
[+] [-] quink|1 year ago|reply
Over what distance?
Make that distance short enough, as has happened with FTTN, or FTTC deployments in a whole heap of places, you're basically building a network that's, and I'll keep this very brief, subpar.
Since you mentioned a UK context there, Openreach rolled out an upgrade that kept the last mile of copper but now just about a decade later they're rolling out Full fibre. Whatever argument copper had, it went out the window near enough a decade ago.
[+] [-] timewizard|1 year ago|reply
The very first part of a dialup modem sound? Where it's playing a tone that reverses phase at regular intervals? That tone is actually designed to disable all the repeaters and echo cancelers that are in your switched circuit.
Also two parallel phone lines are prone to capacitive coupling. I had a case so bad once that one office could pick up the phone and nearly perfectly couple onto their neighbors line and hear all their conversations. It was a 50/50 which port on the PBX recognized the tones and started the call when either of them picked up to dial out.
[+] [-] mannyv|1 year ago|reply
A reasonable decision at the time.
[+] [-] somat|1 year ago|reply
[+] [-] DecentShoes|1 year ago|reply
Australia tried this, it's physically impossible.
[+] [-] tguvot|1 year ago|reply
[+] [-] Synaesthesia|1 year ago|reply
I remember us getting our first modeum, it was 800 baud! Then we moved to 2400, 14.4, 33.6 and eventually all the way to 56k.
[+] [-] bryanlarsen|1 year ago|reply
[+] [-] oldandboring|1 year ago|reply
Like some other commentors I also fondly remember ISDN. Overall I found it to be finicky. Sometimes one channel would just drop, even if a phone call wasn't coming in. And, in order to use a traditional analog phone with your ISDN line, you needed a special powered "TA" adapter or the phone wouldn't ring when a call came in.
[+] [-] timewizard|1 year ago|reply
DS0 is not encoding. It's (pseudo) framing.
> phone calls became digital with
The G.711 encoding in either aLaw or muLaw format.
[+] [-] grishka|1 year ago|reply
[+] [-] sgarland|1 year ago|reply
The fact that all of this worked continues to amaze me, but then, so do mobile phones. I understand at a high level how CDMA works, but it’s just so insane…
[+] [-] unknown|1 year ago|reply
[deleted]
[+] [-] chrsig|1 year ago|reply
[+] [-] p1mrx|1 year ago|reply
Around 2000, I saw a crew pulling new phone lines through the neighborhood because everybody was getting a second line and they were running out, but even after switching to the new copper, we were still stuck at 26400. 20+ years later, it looks like 25/5 ADSL is now available at that address, so the new copper wasn't a complete waste.
[+] [-] wkat4242|1 year ago|reply
[+] [-] icedchai|1 year ago|reply
[+] [-] ljf|1 year ago|reply
[+] [-] DonHopkins|1 year ago|reply
[+] [-] exabrial|1 year ago|reply
Was crazy to think about trying to get your page to load in less than 64k a few years back.
[+] [-] msarrel|1 year ago|reply