[HN Gopher] 56k modems relied on digital trunk lines
___________________________________________________________________
56k modems relied on digital trunk lines
Author : beardyw
Score : 148 points
Date : 2025-03-06 17:19 UTC (1 days ago)
(HTM) web link (hackaday.com)
(TXT) w3m dump (hackaday.com)
| immibis wrote:
| 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.
| ranger_danger wrote:
| 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.
| telotortium wrote:
| 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.)
| hylaride wrote:
| 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.
| immibis wrote:
| Circuits meant for IP didn't convert digital to analog
| and back unless they had to share the line with a phone
| at one end. If you had digital connections to both ends
| of a digital circuit, you'd use all the bits for data.
| topranks wrote:
| 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.
| chrsig wrote:
| ah, good ol' capping out at 26.4kb/s...until 2005
| p1mrx wrote:
| 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.
| bigbuppo wrote:
| 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.
| kstrauser wrote:
| I worked tech support at an ISP. Occasionally customers
| would call in from their brand new subdivision to complain
| about our crummy service. "This house is brand new and we
| only get 26.4. What's wrong with your system?"
|
| And then I had the satisfaction of explaining that Ma Bell
| cheaper out and used pair gains to build out their block
| cheaply. Sorry, call them to complain, or move.
| chrsig wrote:
| i recall some of the same speculation. in my case we wound up
| getting a satellite connection, with a wonderful 600ms round
| trip time.
| sureIy wrote:
| That reminds me of my short time with ISDN and the amazing
| availability to receive calls on the second line without forcing
| me offline.
| stuff4ben wrote:
| 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.
| wkat4242 wrote:
| Yes but with channel bundling you also had to pay twice. One
| channel was only 64k.
| js2 wrote:
| 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.)
| fatnoah wrote:
| > 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.
| hylaride wrote:
| 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...
| shagie wrote:
| 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.
| royskee wrote:
| 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...
| phil21 wrote:
| 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.
| icedchai wrote:
| I worked at an ISP that gave dedicated ISDN and 56k frame
| relay lines as a benefit in the late 90's. T1 would've been
| amazing!
| linsomniac wrote:
| I worked for an ISP back in around '98, and they offered to
| let me terminate a T1 there if I covered the line. I got a
| contract from the phone company for $205/mo for the T1 and
| got it all set up, but they were billing me $250/mo for the
| line. A couple months in DSL dropped, and I got out of the
| T1 contract because they said they couldn't honor the
| contract they wrote because $250/mo was the regulated
| minimum price, and I got 768K DSL for $70/mo. At the time
| everyone was speculating that DSL wouldn't work (crosstalk
| across pairs as multiple people in a bundle use DSL will
| cause it to fail), but they were quickly proven wrong.
| wil421 wrote:
| Back in the day people on forums would list T1 line in
| their signature. My ISDN line was not worthy!
| badc0ffee wrote:
| I had 1.5 Mbps DSL in 1999, and I think nearly all of my
| co-workers either had that or a cable modem with similar
| speed. I think T1s were like 5x the price for the same
| download speed.
| calamity_elf wrote:
| I used to use 128Kbps bonded ISDN at home through BT Home
| Highway and an ISP called Red Hot Ant who had fixed price
| unmetered internet access.
|
| And I accessed the heck out of that connection (until the ISP
| went bust, wonder why?), and was very much a Q3A LPB during
| that time.
| joquarky wrote:
| I had one for work as well in the late 90s.
|
| The other (often overlooked) benefit that ISDN provided was
| 24/7 connectivity in an age of dialup.
|
| Oh and you could spoof your outgoing phone number for caller
| ID ]:D
| xnx wrote:
| 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.
| numpad0 wrote:
| 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.
| OhMeadhbh wrote:
| 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.
| smittywerben wrote:
| You have an eye for quality. They should make an Apple
| voice dongle for that. Inside joke. Signing off.
| Synaesthesia wrote:
| 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.
| cosmotic wrote:
| For some context, wikipedia has a good table and diagram
| of codecs that do well at low bitrates, many of which are
| very old (G.722 from the late 1988, Speex from 2003, Opus
| from 2012 for a few examples)
|
| https://en.wikipedia.org/wiki/Comparison_of_audio_coding_
| for...
|
| https://en.wikipedia.org/wiki/Opus_(audio_format)#Quality
| _co...
| numpad0 wrote:
| I have no _problems_ with Opus or mp3 at low bitrate, in
| the same way I have no problems with microwaved food. I
| just think it 's crazy that no one is doing 4Mbps audio
| while we're routinely streaming 20Mbps video as cheap
| distractions.
| piperswe wrote:
| 4Mbps audio doesn't really make sense when you can just
| about perfectly replicate any human-audible sound in
| ~1.4Mbps
|
| EDIT: I do agree that lossless (or at least high bitrate
| modern lossy, like 256k Opus which is basically
| transparent) should be available in many more situations
| though.
| Sesse__ wrote:
| 192 kHz? That makes no sense, unless you want to have a
| telephone conversation between bats.
| paulmac_ie wrote:
| 192 kHz is the sampling rate, not the sound frequency.
| fhars wrote:
| That still makes no sense, unless you want to have phone
| calls between bats.
| sneak wrote:
| nyquist-shannon means that you only need to sample at
| 192khz if you need to encode signals up to 96khz.
|
| humans can't hear above 20khz. adult humans can't hear
| above 16khz or so, we lose the top end before age 20.
| this means that the standard 48khz sampling rate covers
| the entire human hearing range and then some (0-24khz).
| any sampling rate over 48khz for sound intended for human
| hearing is a total waste.
| IncreasePosts wrote:
| Why do 96 or 128khz sampled audio files sound better than
| 48khz ones? I blind tested and could always tell the
| difference between them, but not between 128 and 192
| toast0 wrote:
| Typically, high sampling rate files are part of a
| different mastering process than what is published as a
| 44.1kHz cd audio or 48kHz dvd audio.
|
| Also, you might possibly be sensitive to resampling
| artifacts if your output device runs at 44.1kHz and your
| file is 48kHz or vice versa.
|
| Audio testing is hard, and testing on yourself is
| tricky... But if you have a sample that you're convinced
| sounds better at high rates than lower rates, I would
| urge you to put it through a tool to resample it down to
| lower rates and see if/when you can tell the difference.
| If the rate isn't an even multiple, it's worth using a
| tool that can dither; dithered resampling artifacts are
| less abrasive than undithered... I had some voice
| recordings to play over the phone, and everything needed
| to be 8kHz u-law; the 48kHz original recordings sounded
| better than 44.1kHz original recordings because one is
| even multiple and the other isn't, but either way, the
| waveforms looked worse than it sounded.
| numpad0 wrote:
| sampling theorem only applies to sine waves. the rate is
| bit like the order of (fourier)series expansion and so
| approximations deviate as rate reduces. how many orders
| is enough depends and is situational
| danbee wrote:
| There is zero point in sampling higher than 48khz. That
| captures all frequencies up to 20khz or so. 192khz is just
| a waste of bandwidth for no actual gain.
| giantrobot wrote:
| That's an absurd bit rate for humans, especially talking
| about voice.
|
| 24-bit samples is ridiculous overkill. That's a huge
| dynamic range that's completely unnecessary.
|
| At 192KHz you'd be able to capture 96KHz signals, far, FAR
| outside the range of human hearing. Human hearing peaks at
| 22KHz so you only need a sample rate of 44KHz to capture
| the total range of human hearing.
|
| For human voice you don't really need better than 16-bit
| samples at 12KHz or so. That's for _great_ quality voice.
|
| The only reason audio mastering is done at huge sample
| sizes and sampling frequencies is to prevent aliasing
| during mixing and to preserve higher frequency harmonics.
| There's absolutely no need for such rates delivering to
| human beings.
|
| Also higher fidelity audio sampling _is_ available for
| phone calls. The issue is more political than technical.
| Cellular carriers don 't like to negotiate higher quality
| calls between one another so inter-carrier calls tend to
| fall back on the lowest common denominator AMR-NB codec.
| Intra-carrier calls don't even reliably pick AMR-WB let
| alone EVS available with VoLTE.
| OhMeadhbh wrote:
| 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.
| xnx wrote:
| 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.
| DecentShoes wrote:
| HD Voice is genuinely what it's called:
|
| https://www.microsoft.com/en-us/microsoft-365/business-
| insig...
|
| They really do sound alot better. It always reminds me of
| the first time I ever made a FaceTime call, in 2010, and
| the high quality audio was just as interesting as the
| video.
| spockz wrote:
| It is the reason why we switched to using FaceTime audio.
| The sound quality is so much better than over the normal
| voice line. I don't know how to reliably get HD Voice.
| xnx wrote:
| Another thing ruined by the cell companies. They should
| be dumb pipes that don't even know what they're carrying.
| madwolf wrote:
| Probably depends on the radio station and area but I work
| in one and we're actually using something much higher
| quality for remote radio, for example:
| https://www.prodys.net/portable-codecs-audio/quantum-
| lite-2/
|
| If course it has to be pre-planned, someone needs to have
| the hardware with them. So sometimes there's a spontaneous
| connection over normal mobile phone. That's something that
| everyone has with them at all times.
| cjrp wrote:
| Apparently it was still used for commentators at the BBC
| until 2023 https://www.linkedin.com/pulse/ode-isdn-paul-
| furley/
| ocal5 wrote:
| Also, you may never beat it's low latency / jitter anymore.
| Sesse__ wrote:
| Modern cellphone networks support wideband codecs, e.g. AMR-
| WB.
| ale42 wrote:
| Is that working across networks, though?
| acuozzo wrote:
| _I think_ it requires SDP negotiation between your UE,
| your EPC, their EPC, and their UE. Assuming all parties
| agree on the use of AMR-WB, then you 're good-to-go.
| ale42 wrote:
| I'm even more mad that sound quality in radio interviews
| actually decreased. People used to use landlines for calling,
| given that very recognizable sound "quality" (which is of
| course nowhere close to what ISDN could do). Now as (almost)
| everybody uses cell phones, quality is sometimes good,
| sometimes very poor depending on network conditions. It's not
| rare to hear the consequences of dropped packets. Sometimes
| it also sounds bad with apparently no drops, not sure why:
| maybe are people using the phone in "hands-free" mode so they
| don't need to keep it in their hands?
| linsomniac wrote:
| I had ISDN for around $75/mo in '94 or '95, flat rate for
| "local" calls. It was fantastic! But then the phone company
| switched it to a metered service (in Omaha Nebraska, USA) and
| the price would have been over $300/mo after that change. I
| was grandfathered in, as long as I didn't move.
|
| I was talking to a sales rep, at the time I worked for USWest
| or QWest, whatever they were called at that time, which may
| have helped, and the sales rep told me "we are being told to
| actively discourage people from buying ISDN".
|
| I get the impression that the phone company hated consumer
| modem use of any kind, because it tied up CO equipment 24x7,
| and they liked the returns on investment they got with people
| paying $25/mo for resources that were used an hour or less a
| day, sometimes with extra revenue from long distance calling.
| And ISDN was just another representation of that.
| badc0ffee wrote:
| I thought VoLTE was supposed to fix that, at least for mobile
| phones.
| xenadu02 wrote:
| 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.
| Sohcahtoa82 wrote:
| 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.
| cantrecallmypwd wrote:
| 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.
| wkat4242 wrote:
| 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.
| icedchai wrote:
| 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.
| hylaride wrote:
| 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.
| wkat4242 wrote:
| True, though in those days that didn't really matter except
| for gaming. The bandwidth was so low and the web going in
| content so fast that the local uplink bandwidth was usually
| congested causing delays due to queueing and pending
| acknowledgements. Switches and routers weren't quite as
| optimised for low latency either. A lot of local networks
| were still 10base2 (or 10baseT with hubs, not switches) so
| collissions added further latency.
|
| What I loved the most about ISDN was the quick call setup.
| Took like 1 second max and you had a 64kbit channel. 56k
| modems went through a dialling phase, a connection phase,
| endless handshaking...
| ljf wrote:
| 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.
| rasz wrote:
| Hey, in early 00 I briefly worked for an ISP trying to do
| rural Portugal/Spain satellite internet (to exploit rather
| large subsidies offered at the time)! Afair it was 1-2 Mbit
| downstream for all subscribers in one area from geo
| stationary sat with 500-1000ms pings. Almost unusable for
| normal browsing. Company was from defense background and from
| my limited understanding at the time they were piggybacking
| on some military leftovers tech. Idea was to use commercial
| Wifi to link local customers to central location with some
| magic proxy server trying to hide all that latency.
| roygbiv2 wrote:
| I remember reading about this back in the day. I seem to
| recall the latency being a killer.
| giantrobot wrote:
| The first cable Internet service I had was telephone return.
| Downstream was over the cable modem at ~512Kbps (IIRC) but
| upstream was over a dial-up modem.
|
| It was cool having a fast downstream but the slow upstream
| over finicky dial-up was a pain in the ass. If the dial-up
| dropped the in progress downloads all died because no ACKs
| could be sent. Gaming was no better than plain dial-up since
| your upstream had the same shitty latency as plain dial-up.
| OhMeadhbh wrote:
| 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.
| plorg wrote:
| 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.
| iptel wrote:
| 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.
| timthorn wrote:
| Internet Thruway from Nortel allowed multiple ISPs to use
| the same local termination hardware; If I remember the
| details correctly, different national numbers could be
| terminated on the same box, with the subsequent IP traffic
| routed to the correct ISP.
| function_seven wrote:
| Wikipedia has good info on how RespOrgs handle this:
|
| https://en.wikipedia.org/wiki/Toll-
| free_telephone_numbers_in....
| timthorn wrote:
| Yes, the Intelligent Network was the big thing in the 1990s.
| It allowed for routing as you describe as well as calling
| cards and many other features:
| https://en.m.wikipedia.org/wiki/Intelligent_Network
| pantulis wrote:
| Oh the joys of watching terminal logs with SS7 data frames!
| xattt wrote:
| Was there any way for the customer to somehow interact
| with SS7 frames?
|
| We've had techs come to our home in Canada in the 1990s,
| and I remember being fascinated with their _mystical
| toolbox phone_ that seemed to uncover hidden phone line
| functionality. Almost like the whip in Indiana Jones.
| pantulis wrote:
| I don't think so, but who knows. In my case I was working
| at a telco so everything was very obvious at the dev
| environments.
| cantrecallmypwd wrote:
| 911 and 0 (operator).
| shrubble wrote:
| Yes, but it would usually be based on the first 3 or 6
| numbers of your phone number. The first 3 are of course "area
| code" and the 6 are called "NPA-NXX". This has blurred some
| due to line number portability and cell phones.
| mschuster91 wrote:
| Yes, at the very least 911 (US) / 112 (EU) run on that
| system. For SIP numbers routing depends on the address you
| set up in the phone provider's portal, so if you're using
| bring-your-own-SIP to provide landline phone service in your
| house, you absolutely have to keep the address current or you
| risk dialing 911 and ending up on the dispatch of your old
| addres...
| rasz wrote:
| > 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?
| icedchai wrote:
| This did happen eventually. In the late 90's, various
| companies (Cisco, Ascend) provided boxes that could handle 24
| modems on a single T1 port (PRI or channelized T1.) This
| massively improved ISP port density. Before that, it was
| racks and racks of modems...
| actionfromafar wrote:
| IIRC it was the only way to support 56k.
| icedchai wrote:
| Yes! The ISP side needed to be digital to get a 56K
| connection.
| timthorn wrote:
| I was working for one of the telco equipment firms around
| that time. We made a box that would terminate TDM trunks and
| had it in the lab.
|
| I was installing Windows 2000 on a PC in the lab (manual disk
| swapping required) when, hidden behind another rack, several
| shelves full of physical modems all started calling the box
| at once, speakers on.
| wffurr wrote:
| I am trying to imagine the racket that must have made.
| Amazing how vivid that modem sound is in memory.
| linsomniac wrote:
| You're thinking about the Livingston/Lucent Portmaster 3. htt
| ps://osmocom.org/projects/retronetworking/wiki/Livingston...
|
| These were great boxes, and the only way you could get 56K
| was to call into an ISP with one of these or similar on their
| end -- the trickery that allowed 56K relied on one end being
| fully digital.
|
| I was working for an ISP around that time and we had a bunch
| of Portmaster 2s connected via RS-232 cables to piles of
| modems, some rackmount some just stacks and stacks of US
| Robotics Sportsters. Sometimes modems would get wedged and
| we'd have to reboot them or "busy out" the line that they
| were on. Harder for the modems that were an hour away.
|
| When the transition happened we were able to get rid of all
| those wires and just plug in one small phone cable for the
| T1, another for Ethernet, and terminate 23 lines. The
| Portmaster would treat all the modems as a pool and route
| calls to whichever was available, and once a call was done
| would run some testing on the modem before putting it back
| into the pool. It was like a space age rocket ship! At one
| point I was driving around with $50K worth of Portmasters in
| the trunk of my car, hoping I didn't get rear-ended. They
| were not at all cheap, but they were worth it.
| iramiller wrote:
| Similar story with Portmaster 2s and a wall of modems layed
| out. The resulting blinking lights acted like a load
| monitor of sorts as the activity would spread across the
| wall as customers dialed in after work and signed off at
| night. Not mention a wall of flashing red lights made a
| pretty good picture of 'the internet' for those just
| starting out on this adventure in 1997.
| kstrauser wrote:
| Oh man. I was talking to my wife's acquaintance and he was
| excited to talk shop when he found out I was technical. He
| worked at "this small company you've never heard of,
| Livingston." "As in, Portmaster?" "You know about that?!"
|
| Yeah, friend. I'm very familiar, and it was amazing tech.
| It sure kept the data center cooling system busy, though.
| ubercore wrote:
| Compaq Presario catching strays.
| grishka wrote:
| 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.
| kragen wrote:
| LZW?
| oldandboring wrote:
| 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.
| hackthemack wrote:
| 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...
| mannyv wrote:
| 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.
| quink wrote:
| 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.
| quink wrote:
| OK, had a look through the linked paper. The big graphs, on
| page 8, tell you that if you decrease the twist length -
| which would entail relaying all the copper in the entire
| network, at which point you may as well put down fibre
| instead - you will get -20 dB at 10 GHz over a distance of
| 0.5m, 50cm, less than two feet, instead of -25 dB in the
| worst case.
|
| In other words, instead of losing 99.7% of the signal over
| that distance, it'll only lose 99% of the signal. Sure, it
| helps, but consider me underwhelmed.
| timewizard wrote:
| 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.
| tguvot wrote:
| https://en.wikipedia.org/wiki/G.fast
| DecentShoes wrote:
| It can carry 1 gigabit, over a few metres. I.e. Not even the
| length from the street to your house.
|
| Australia tried this, it's physically impossible.
| somat wrote:
| 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
| marcus0x62 wrote:
| 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.
| twic wrote:
| If the copper isn't in good enough condition, you can always
| try with wet string instead:
|
| https://www.revk.uk/2017/12/its-official-adsl-works-over-
| wet...
| pjdesno wrote:
| 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.
| Synaesthesia wrote:
| 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.
| bryanlarsen wrote:
| 800 baud? Do you mean 300 baud? 800 baud is not a standard
| speed so if they did exist you'd have to supply both ends of
| the connection..
| Synaesthesia wrote:
| Oh yeah it was 300!
| bryanlarsen wrote:
| Darn, I was hoping it was some sort of oddball thing. Those
| are always interesting.
| timewizard wrote:
| > Using the Digital Signal 0 (DS0) encoding
|
| DS0 is not encoding. It's (pseudo) framing.
|
| > phone calls became digital with
|
| The G.711 encoding in either aLaw or muLaw format.
| pimlottc wrote:
| 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.
| kreddor wrote:
| 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?
| aa-jv wrote:
| 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.
| DonHopkins wrote:
| There was a time when 300 and 1200 baud modems cost about
| $1/baud.
| exabrial wrote:
| Man I wish we still had slow connections, given all the dumb crap
| on webpages these days.
|
| Was crazy to think about trying to get your page to load in less
| than 64k a few years back.
___________________________________________________________________
(page generated 2025-03-07 23:01 UTC)