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.
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.
Absolutely, when call hits local switch it can be terminated differently based on its location. Particularly pertinent for modem based services in the 90s. A single national dialup number would terminate on 100s of local pops and routing decisions would be done to keep traffic as local as possible.
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.
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.
I think it was ubiquitous. NPR in the 90s and 2000s used ISDN to allow many of their commentators to work from home. I think where you hear those crazy 8KHz clipped calls is where it's not an option. Mostly these days remote radio and podcast interviews I hear remote participants sound more like they're on mobile phones: variable voice quality with an almost unbearable latency.
24 [bit] * 192 [kHz] = 4.608 [Mbps]. Maybe not sensible to do so, but many people could have Discord calls in uncompressed "high-res" WAV. It's crazy that there aren't even 16bit/44.1k modes in most voice call apps.
The economics probably aren't that great to send uncompressed voice into the data center. If you have a business that gets charged XX cents (or more likely .00XX cents) per GB of traffic and you can cut that in half by using compression... I think people will opt to use compression.
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.
The most bang for buck "employee benefit" I ever offered to my guys back in the earl 00's was a T1 line to their home for free.
We could do this since local loops to most folks were about $150-200/mo, and we already had a channelized DS3 terminated at our rack at a local datacenter for our phone banks. If you bought your own DS1 retail you'd be paying upwards of $1k/mo back then to a provider.
It was by far the best "stickiness for dollar" investment into employee benefits I've ever found back then or since.
I was one of those SAs, circa 1998-2000. We also had an on-call kit with a Nokia Communicator so we weren't completely stuck at home while on-call.
Fast-forward to 2025, and I now have dual 1Gbps symmetric fiber connections (AT&T, GFiber) into my home from opposite sides of the house. (It's totally gratuitous and I'll probably cancel GFiber in a few months, but I wanted to have it wired up so I could more quickly start service in the future.)
Ha! My mom worked as a build engineer at BNR (later Nortel) in the 1990s and we got a free 2nd phone line for her to dial into work (99% used by me and my brother for internet). She could have gotten ISDN had it been available in our small town, but alas...
One of my internships in college was at Sun Microsystems in the org that provided this connectivity to employees. My job was to automate pushing updates to connection software and modem firmware down to clients, but I ended up doing a lot of technical support as well.
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.
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.
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.
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.
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.
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.
Or gaming. I never got good at quake because of it. IIRC they added hardware compression to the later versions (I think starting at 33.6?) that added latency, too.
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.
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.
More than one A-to-D conversion would knock it down to no more than 33.6. Pair gain units would cause problems. Bridge taps and load coils could also be problematic, but that was much more of a concern on DSL. Older amplifiers had very narrow filters and would also cause slow speeds. Echo cancellation hardware would ignore the in-band signal to get out of the way and cause problems.
As there was no legal compulsion to get them to act Bellsouth wouldn't do anything to help slow connect speeds for internet dialup. The trick was to lie and say you were having problems sending a fax, then they were required to act. They wouldn't even worry about testing first, as it was quicker to just re-engineer the line to the best practices of the day.
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.
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.
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.
Exactly. More specifically, Internet servers in data centers connected themselves to the IP network, not the phone network (not surprisingly), so they almost always had an uplink significantly faster than 56 Kb/s. And the analog local loop had encodings that could transmit at 56 Kb/s. But these encodings were not compatible with the analog-digital conversion used in phone network backbone.
While today you'd probably expect that the IP network could connect to every phone branch office where the local loops were connected to the phone network, that wasn't necessarily the case - Internet data would usually have to travel some of its way over the phone network backbone, with the problematic digital encodings. V.90 and related standards allowed the phone network to accept the digital data directly from ISPs and send it in digital form to the branch office, without attempting a digital to analog to digital conversion to inject it as digital voice into the phone network. That's why the upload speed couldn't be improved via this method - it would still need to undergo analog-digital conversion to travel across the phone network to the ISP where it could enter the IP network. (V.92, a later standard, improved upload speed to 48 Kb/s via fancier signal processing trickery that could survive the digital voice conversion.)
All the early metropolitan or long-haul fiber (mostly SONET) networks were digital aggregations of various circuit-modes (DS*) in those days. It made sense since the phone network was pretty much the only long haul network around and even the pure-IP networks didn't yet have enough of a market for alternative protocols. I've been out of the core-networking loop for awhile, but my understanding is that most modern long-haul networks are ethernet over OTN.
The phone companies had enormous sway over the development of these longer haul protocols. The debate around packet sizing almost always favoured smaller cells (especially ATM), which was more ideal for voice - with the added overhead for more standard IP packets. They were also often very connection-oriented, with all the extra equipment overhead required.
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.
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.
Wikipedia has good info on how RespOrgs handle this:
https://en.wikipedia.org/wiki/Toll-free_telephone_numbers_in....
Absolutely, when call hits local switch it can be terminated differently based on its location. Particularly pertinent for modem based services in the 90s. A single national dialup number would terminate on 100s of local pops and routing decisions would be done to keep traffic as local as possible.
I could tell what connection speed my modem was going to be by the sound of the handshake. There were distinct sounds for all the different modes.
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.
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.
That reminds me of my short time with ISDN and the amazing availability to receive calls on the second line without forcing me offline.
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.
I think it was ubiquitous. NPR in the 90s and 2000s used ISDN to allow many of their commentators to work from home. I think where you hear those crazy 8KHz clipped calls is where it's not an option. Mostly these days remote radio and podcast interviews I hear remote participants sound more like they're on mobile phones: variable voice quality with an almost unbearable latency.
Every once in awhile the stars align and I randomly get an "HD" voice call. It's disorienting to both me and the other party how good the quality is.
24 [bit] * 192 [kHz] = 4.608 [Mbps]. Maybe not sensible to do so, but many people could have Discord calls in uncompressed "high-res" WAV. It's crazy that there aren't even 16bit/44.1k modes in most voice call apps.
Speech compresses really well, with modern techniques you can get it down a lot.
The big issue with analogue landline phone calls is the audio bandwidth is so limited. It's not the full frequency spectrum, most of it it cut off.
The economics probably aren't that great to send uncompressed voice into the data center. If you have a business that gets charged XX cents (or more likely .00XX cents) per GB of traffic and you can cut that in half by using compression... I think people will opt to use compression.
You have an eye for quality. They should make an Apple voice dongle for that. Inside joke. Signing off.
Also, you may never beat it’s low latency / jitter anymore.
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.
The most bang for buck "employee benefit" I ever offered to my guys back in the earl 00's was a T1 line to their home for free.
We could do this since local loops to most folks were about $150-200/mo, and we already had a channelized DS3 terminated at our rack at a local datacenter for our phone banks. If you bought your own DS1 retail you'd be paying upwards of $1k/mo back then to a provider.
It was by far the best "stickiness for dollar" investment into employee benefits I've ever found back then or since.
There was also that period of time when Ricochet was available in some places.
https://en.wikipedia.org/wiki/Ricochet_(Internet_service)
Wireless 56k baud. So you could take your luggable laptop circa 1994 with you and dial in to work... given you lived in SF.
Oh man I forgot about Ricochet. I remember they had service in NYC too, and it turns out also in a few other big markets. https://www.nytimes.com/2001/08/16/technology/ricochet-netwo...
I was one of those SAs, circa 1998-2000. We also had an on-call kit with a Nokia Communicator so we weren't completely stuck at home while on-call.
Fast-forward to 2025, and I now have dual 1Gbps symmetric fiber connections (AT&T, GFiber) into my home from opposite sides of the house. (It's totally gratuitous and I'll probably cancel GFiber in a few months, but I wanted to have it wired up so I could more quickly start service in the future.)
Ha! My mom worked as a build engineer at BNR (later Nortel) in the 1990s and we got a free 2nd phone line for her to dial into work (99% used by me and my brother for internet). She could have gotten ISDN had it been available in our small town, but alas...
> All paid for by the company they worked for.
One of my internships in college was at Sun Microsystems in the org that provided this connectivity to employees. My job was to automate pushing updates to connection software and modem firmware down to clients, but I ended up doing a lot of technical support as well.
Yes but with channel bundling you also had to pay twice. One channel was only 64k.
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.
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.
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.
https://www.newscientist.com/article/2317040-ordinary-copper...
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.
They did it for efficiency. The observation was that the human voice doesn't use most of the audio spectrum, so they optimized everything for voice.
A reasonable decision at the time.
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.
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.
Or gaming. I never got good at quake because of it. IIRC they added hardware compression to the later versions (I think starting at 33.6?) that added latency, too.
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.
ah, good ol' capping out at 26.4kb/s...until 2005
We were stuck at 26400 until 2001, when DOCSIS reached the area. I recall hearing speculation that a https://en.wikipedia.org/wiki/Pair_gain was the cause.
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.
More than one A-to-D conversion would knock it down to no more than 33.6. Pair gain units would cause problems. Bridge taps and load coils could also be problematic, but that was much more of a concern on DSL. Older amplifiers had very narrow filters and would also cause slow speeds. Echo cancellation hardware would ignore the in-band signal to get out of the way and cause problems.
As there was no legal compulsion to get them to act Bellsouth wouldn't do anything to help slow connect speeds for internet dialup. The trick was to lie and say you were having problems sending a fax, then they were required to act. They wouldn't even worry about testing first, as it was quicker to just re-engineer the line to the best practices of the day.
i recall some of the same speculation. in my case we wound up getting a satellite connection, with a wonderful 600ms round trip time.
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.
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.
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.
Exactly. More specifically, Internet servers in data centers connected themselves to the IP network, not the phone network (not surprisingly), so they almost always had an uplink significantly faster than 56 Kb/s. And the analog local loop had encodings that could transmit at 56 Kb/s. But these encodings were not compatible with the analog-digital conversion used in phone network backbone.
While today you'd probably expect that the IP network could connect to every phone branch office where the local loops were connected to the phone network, that wasn't necessarily the case - Internet data would usually have to travel some of its way over the phone network backbone, with the problematic digital encodings. V.90 and related standards allowed the phone network to accept the digital data directly from ISPs and send it in digital form to the branch office, without attempting a digital to analog to digital conversion to inject it as digital voice into the phone network. That's why the upload speed couldn't be improved via this method - it would still need to undergo analog-digital conversion to travel across the phone network to the ISP where it could enter the IP network. (V.92, a later standard, improved upload speed to 48 Kb/s via fancier signal processing trickery that could survive the digital voice conversion.)
All the early metropolitan or long-haul fiber (mostly SONET) networks were digital aggregations of various circuit-modes (DS*) in those days. It made sense since the phone network was pretty much the only long haul network around and even the pure-IP networks didn't yet have enough of a market for alternative protocols. I've been out of the core-networking loop for awhile, but my understanding is that most modern long-haul networks are ethernet over OTN.
The phone companies had enormous sway over the development of these longer haul protocols. The debate around packet sizing almost always favoured smaller cells (especially ATM), which was more ideal for voice - with the added overhead for more standard IP packets. They were also often very connection-oriented, with all the extra equipment overhead required.