AT&T's '60s Modem That Won't Die

who remembers dial-up internet well for youtube analytics probably about 40 of you i'm 32 years old and probably in the last generation that's likely to remember dial-up as an everyday fact of life since most of you are as old or older than me probably a lot of us remember it and the memory always goes something like this if you grew up in the 90s in particular that's going to be the modem experience that you remember the first part of course is dialing the modem emitting touch tones to dial up the other party either your internet service provider or a friend who you're going to death match with the second part is the handshake which is the two modems talking to each other to determine what their common supported features are and what the line can tolerate in terms of speed so they can settle on a speed and feature set to use for the data connection now these were daily experiences for most of us but they're actually very advanced features that didn't become available in modems until very late in the modem lifespan or at least they didn't become available in the majority of modems i won't dispute that this sound that we're all familiar with is the sound of the internet pretty much everyone ever dialed up to the internet probably used a modem that worked like this but if you're just a little bit older than the set that grew up with the internet you might regard these noises as sort of newfangled and shiny still despite the strong cultural association between the two dial-up modems were only the primary method of getting on the internet for maybe five to eight years before they were displaced heavily by broadband and are now almost non-existent however 20 years before the internet existed modems were around and people were networking computers but the modems they had were a lot different a lot slower a lot dumber the first commercial computer modem originated not in the 80s not in the 70s but in 1959 and that year at t also known as the bell company put out their first modem the model 101 data phone data phone is what they called modems for the first couple decades that they existed awkward name but i guess they thought modem was a little too technical there are no verifiable pictures of the 101 on the internet or any resource i found there's just this one apocryphal jpeg that's been floating around for years which doesn't actually say it's a 101 so i'm not convinced that's what it looked like but for 1959 it very well could have been this massive however bell did make several variants the 101 a b and c which as you can see in this picture here were integrated into teletype machines in the early years the majority of modems were very likely used with teletypes they were very commonplace at that time the full name is teletypewriter and as the name suggests they're just typewriters that can be operated at a distance the simplest way to use a teletype was to connect it to another one either directly with a pair of wires strung between two buildings or over an automated switching system called telex that was much like the phone network but just for teletypes once you were connected whatever you typed on your machine would get typed by the machine at the other end and whatever they typed would get typed by your machine and that's it they just type in a distance but the way the teletypes identified which letters you were typing was by sending different series of pulses down the line each one identifying a character from a predefined table this made teletypes one of the earliest types of digital communication since they were originally made for use with the telegraph system in the late 19th century however they remained relevant to business communication well into the 20th century so in the early 60s when digital computers started to become viable on a large scale teletypes were adopted as a common interface device crt-based terminals were not a common site in the front half of the 60s but teletypes were and since they already used a digital interface they were an obvious choice as input output devices for computers in this role teletypes became known as ttys for short and they were probably the most common way people interacted with computers for the first half of the 60s that first modem the 101 only transmitted at the breathtaking pace of 110 bits per second or 110 baud now it takes a very long time to explain what the word bod means but in this case i'm using it to mean bits per second because nobody ever made a short word that means that in other cases baud does not mean bits per second but in this video it does so for people who want to comment and be pedantic don't i know what i'm saying and why any way you slice it 110 baud is not fast for instance here is the b movie script being transmitted at 110 baud and i'm pretty sure you could watch the entire movie in the time it would take to send the script at this speed 13 characters per second was probably fine for most teletypes since many of them couldn't print any faster than 10 characters per second anyway and the key travel on these things was often so long you'd be hard-pressed to type any faster than that so really a match made in heaven however people did have things that could transmit faster than a teletype computers certainly but also people had punch card readers and paper tape readers which could transmit as fast as they could move the tape or the cards and the faster you transmitted data the shorter your phone call could be which meant you paid less for it this meant that there was definitely an incentive for faster modems and at t did make some in 1962 at t did put out a faster modem a modest offering really just the next obvious step in their existing product line but for whatever reason the ripples from that product release were felt for over half a century and are still affecting us today that modem was the model 103 data phone and i don't have any good pictures of that one either but we do have good illustrations demonstrating that it was like randy johnson a big unit it was also a much faster unit it transmitted about three times quicker than the 101 at 300 baud but in most other regards was pretty much the same thing just quicker and smaller however for murky reasons the 103 would go on to become one of the most enduring data communication standards in history case in point here is a modem from 1979 some 16 years later which transmits at 300 baud and here is a modem from 1983 21 years later which transmits at 300 baud here's a modem from 1989 37 years later which transmits at 300 baud if you ask it to and there are devices being made as you watch this video today current production products which also transmit at 300 baud and every one of these will talk to a bell 103 data phone i don't even need to tell you that it didn't take 40 years to improve the speeds of modems you know that we all know it doesn't work that way even if you're 19 and you weren't there for any of this stuff electronics just moves faster than that and you'd be right by 1975 you could get a modem that would do 1200 baud which is at least four times faster than this thing so what were people doing buying modems this slow in 1983 let alone 1999 let alone now what possible explanation could there be for this well i can't answer all the questions but i can fill in some of it and it might help since we have a couple bell 103 compatible modems here of different types for us to go through and see how they behave talk about how they work and then we can come back and tackle the question of why they managed to define network computing for a couple decades and are still relevant 59 years later of all the gear i've assembled to demo this today i'm going to start by bringing us back to this guy here this is the novation cat it is from 1979 it is a 300 modem apparently one of the first modems to gain large-scale hobbyist uptake in the market so apparently fairly legendary as a result the device itself is not terribly sophisticated but the first thing we have to do is address the elephant in the room what are these about it sure doesn't look like much of a modem does it i mean these things here look like steam vents or something and there's actually nowhere to plug in a phone line at all so on first glance it's not at all clear how this thing could be a modem well collectively these things are called an acoustic coupler and this device is called an acoustic modem and it's called that because it uses sound waves to connect to the phone line as you may recall computers used to have serial ports on them they're a very simple form of digital communication they send ones and zeros in the form of plus or minus 12 volts one is 12 volts a zero is minus 12 volts and that's it it's nominal anyway sometimes they're higher sometimes they're lower but it's about 12 volts before usb and ethernet this was the best way to get data in and out of a computer to anything else well there was that but so when you got online you plugged your modem into that port and it turned your clean digital ones and zeros into awful squawking noises as anybody who picked up the phone while they were on aol will recall but the purpose of the modem was not really to make noises it's more accurate to say that modems create audio frequency signals which if put into a speaker will produce sounds you can hear but they're not supposed to do that they're never supposed to actually wobble the air so why do modems produce something sound like if they're not meant to produce sound well the reason is they're meant to send data over the phone system which is designed to send sound only not data suppose your serial port is sending a file as a bunch of ones and zeros and it has to send a whole bunch of ones one one one one one one one one one well if you look at the port what you're going to see is plus 12 volts continuing till the end of the string of ones and then it'll drop back down when a zero comes well the phone network it doesn't do that it only passes signals that are shaped like the human voice which according to the phone company means it has to wobble at between 300 and 3 400 oscillations per second since your serial report doesn't necessarily do that its signals that are outside of that range just get filtered out and thrown away basically the solution to this problem is the concept of modulation which i've spoken about before the basic idea is if you have a signal that won't pass through a particular medium you put it inside of a signal that will pass through that medium the modem turns your digital ones and zeros into oscillations that the phone system will accept process called modulation the modem at the other end receives those and turns them back into ones and zeros process called demodulation that's what moda means modulator demodulator the result happens to be that your ones and zeros become something that a speaker can reproduce as sound but that's incidental the whole point is just to cheat the phone network which is why most modems like this one skip the step of actually making sound and just plug straight into the phone line but this modem can't be connected to a phone line doesn't have a jack for it however if we hook it up turn on give it a signal from a computer it sure will make modem noises sure sounds like the modem noises we're familiar with but with your 90s modem the only time you actually heard those sounds was during the dial-up process because they were actually a diagnostic tool the modem had a speaker on top that it used to make those noises just during the connection process you could diagnose it if something went wrong very few people actually knew what to do with those sounds but that is the only reason they were there you could actually turn them down or off completely and it wouldn't affect the function of the modem at all but with this one those sounds are critical they're being produced by a speaker in this cup here and in this cup there's a microphone and they happen to be spaced and about the yeah you put a phone handset in it that's that's that's what it's for yeah the modem has a speaker and a mic and the handset has a speaker and a mic they're flipped so each one meets the other one when the modem produces its signal as actual oscillations in air the phone handset turns those into electrical oscillations and then when the other modem's oscillations come back up the line the phone turns them into sound which the modem on this end then turns back into the electrical oscillations that it wanted so notionally the signal this modem gets from the sound is the same as the signal that was actually on the wire it just has to be audio for a sixteenth of an inch this looks kind of clever but you've probably already guessed it's terrible this was not a great way to do things it was just unfortunately necessary for a while some viewers might be aware that it used to be illegal to plug your own equipment into the phone network but by 79 that hadn't really been true for over a decade in fact in 77 you could buy a modem with a phone jack like this vatic here just plug it straight into the wall my other modem here from 83 will also do that but here's an issue of popular science showing that acoustic modems were still available for sale in 1984. in fact novation was still selling the cat for 189 they were selling a direct attached version as well which was only ten dollars more so acoustic modems continued to be in vogue despite their drawbacks and what drawbacks were those while the design of the acoustic coupler is clever when you have a phone on there it's going to produce a resonant cavity in the interface between the speakers and microphones that's going to tend to destroy the much more precise signals used by virtually every other modem modulation that was ever invented this could get even worse if you didn't seat the handset perfectly because you could put it on here and it could pop out a little or you could get a little further on the top than the bottom it's it's it's very it's very messy it's very hard to get it to actually see in there all the way the coupler also doesn't fully isolate external noises so if i were to yell into this that would probably make its way into the signal and i would guess that the echo control and filtering circuitry in the telephone itself are none too kind to precise modem signals so while you probably could put a higher bit rate modem signal into this i doubt it would never make it to the line intact like i said i'm guessing about a lot of that but as i said pretty much every acoustic modem i've ever found is limited to 300 baud in fact if you look at that popular science modem roundup all the ones that can go faster are direct connect designs so what gives if you could buy a modem that was smaller simpler more reliable possibly faster and just not silly why would you buy one that wasn't any of those things well one reason is that for a very long time telephones were permanently installed fixtures when the phone company came to your house to put in a phone line they would also bring a phone and hardwire it straight into your wall you couldn't unplug it to connect a modem while that had changed for most new installations by the end of the 70s there were still plenty of houses that had hardwired phones also as we moved into the 80s tiny portable computers started to become feasible like the trs-80 model 100 which was apparently popular with traveling businessmen if you were staying in a hotel room you couldn't necessarily unplug the phone in your room to get at the jack to plug in your modem but if you had an acoustic coupler you were set to jet people would ostensibly even use acoustic couplers with pay phones in order to send a quick email while they were on the go there might have been other issues the acoustic modem addressed but at any rate it remained popular throughout the 70s and 80s and since virtually all of them were limited to 300 baud and even the inexpensive direct connect modems on the market were also limited to 300 baud that remained the lowest common denominator for modem speeds throughout those decades beyond the acoustic versus direct distinction however there was virtually no difference in how any of these 300 modems functioned so i'm going to make a connection between the two different types to show you how they worked all right here's the setup we have two imaginary houses here this is all me over here and this is my friend jim who doesn't exist in an apartment across town now my side i have a terrible knockoff bell 2500 set in this distasteful color of beige and i have the novation cat acoustic coupler modem and i have that plugged into my weiss terminal now this is a type of device often referred to as a dumb terminal or in past decades a glass tty because its purpose originally was to simulate a teletype but instead of smacking out the received characters onto paper it saves them in memory and prints them on a screen now this isn't quite a computer it doesn't have any programs per se and you can't program it the only thing it does is display text that it's received and send text that you type on jim's side he has an actual 2500 set from western electric the good stuff and then he has the mira mini modem that's my 1983 direct attach 300 modem and then he has a laptop now this is running a much later completely anachronistic operating system windows 98 however i'll be running hyper terminal on this which is a program that emulates a dumb terminal which in turn emulates a teletype so i have two teletypes here the reason i'm using such basic appliances here is because we want to see exactly what these modems are sending if i were using like a modern network stack such as tcp that might cover up some of what the modems are doing maybe there will be errors in the bitstream or whatever that they quietly correct by re-transmitting bytes not so here whatever this computer sends will be exactly what this one displays unless something goes wrong ah foreshadowing so i'm ready to connect to jim now you might think that the first step is to take the handset and put it on the coupler so that the modem can dial his number but neither one of these modems can actually dial on their own there's a couple reasons for this but one is that in 1979 not all phone lines actually had touch tone dialing it had been around for quite some time but the bell company was still charging people to enable it so a lot of lines still just did pull styling like these old rotary phones so this wouldn't be able to dial on there because pole styling works by disconnecting and reconnecting the phone line rapidly and since this has no electrical connection to the line it can't do that jim's modem is directly connected so it could do this but dialing circuitry is fairly sophisticated and as i'll show you in a bit these modems are not very sophisticated but probably a bigger reason is the handshaking process here's what the handshake process looks like first i call jim then i say hey jim i've got that file you wanted and he says great i'll answer you originate so jim puts his modem in answer mode when he does so a deafening tone blasts down the line so hopefully i've pulled the handset away from my ear at this point he then hangs up his telephone set because the modem has the one feature which direct connect offers of holding the line open for as long as it's switched on and then on my side i set my modem to originate and then i set the receiver on the coupler and that was the handshake process you call each other and discuss which settings to use on your modems you see these modems even the directly connected ones don't control the call in any way they don't begin it they don't end it humans set the call up and then you turn your modems on and they just start going they assume that the connection has been established and all the settings are already set with the handset on the coupler the ready light on the cat illuminates which indicates it's receiving the carrier signal from jim's modem and likewise there is a carrier detect light on there which just means the two modems are hearing each other at this point we're connected and we can send data so now if jim types some junk on his laptop here you'll see it show up on the terminal and if i type on my terminal you'll see it show up on the laptop and you can actually hear this if we pick up the handset here there's the carrier and now when jim types let me get that a little closer there this modem connection is so simple that you are literally hearing the binary code representing different letters on my keyboard now we can just use this to chat at this point jim types and hits enter and then i type and hit enter but probably a lot more efficient just call each other on the phone at that point now if we both had computers then we could maybe use kermit or z modem to send a file back and forth but i don't have that fortunately jim has hyperterminal which is capable of sending any file as plain text so let's do that jim is now sending me the script to b-movie at 300 bits per second and although that is quite a bit faster than the 110 baud we saw earlier we're still going to be here for a while and that's a bummer because i won't know when it's done it could be sitting here for hours and when it's finished jim is going to hang up but i'm not going to get any indication on my end that that happened you see my machine doesn't even know it's connected if i pull the handset out of the coupler you can hear it still screaming away jim's modem is sending me the bits for b-movie but they're no longer appearing on the screen because the sound isn't getting there anymore but if i just put the handset back on there there we go it's back i assume you don't know the script to be movie by heart i hope you don't anyway but if you did you might notice that there's a gap the letters that would have been sent when this was off the coupler are just gone it picked up several seconds later this is because jim's machine has no idea that mine just went away it just kept on sending bits out the serial port and the modem just kept on modulating them even though there was no computer at the other end receiving them i can actually uh pick up the handset here just sort of move it back and forth on and off the coupler and when it's close enough it'll start demodulating and when it gets far away it'll stop demodulating now i can turn the modem off still going uh and then turn it back on put this bad boy on here and there we go it's possible for the computers to detect the carrier loss and give up on transmitting but the point is that the modems can't do that they don't have the intelligence to do that at all in fact these modems are as simple as they could possibly be while some kinds of modulation are hard to understand and in fact later modems are absolutely baffling the bell 103 is dead simple this is because it uses a modulation called frequency shift keying or fsk which is so simple i can explain it in one sentence if you want to send a zero you beep at one frequency and if you want to send to one you beep at a second frequency i'm not kidding that's literally it this is a block diagram from a 103 compatible modem the primary components are the frequency generator and discriminator the generator makes tones and the discriminator tells you if it hears a particular tone when the discriminator detects the tone for 1 it outputs positive 12 volts and the rest of the time it outputs negative 12 volts that's it there is no further capability in the receiving circuitry the generator does the exact same thing in reverse if the computer sends 12 volts it puts out one tone and if the computer sends minus 12 volts it puts out the other tone those are the only parts of the modem that are active the rest are just support components timing crystals and filters and that sort of thing this modem is not aware of any state it doesn't know whether it's connected or not it doesn't know whether there's another modem on the other end it doesn't know anything all it does is listen for noises and make noises for this to work of course the modems have to agree on what's a one and what's a zero the bell 103 established those two frequencies and they've never been changed and the modems have to be able to tell which one of them is sending the signals if they both use the same pair of frequencies then they might hear their own data as if it were coming from the other modem but to solve this problem the bell 103 uses two different pairs of frequencies one for the answer side one for the originate side that's why when i called jim he said he'd put his modem on answer that way i knew to put mine on originate so they don't collide with one another i don't think it matters who does which as long as both modems are on different settings now if i haven't made my point yet this system is so simple that the other end of the connection doesn't actually have to be a modem for instance here's a recording of a bell 103 modem if i put this up against the mic here how about that it's being demodulated it doesn't care if there's no real modem on the other end that doesn't matter in the least a 90s style dial-up connection is an intimate conversation between two modems they're not just sending through the data that the computer is transmitting they're also having a conversation directly with one another talking about the state of the line and whether it need to be any changes like changing in and out of data mode to voice mode or maybe shutting down the connection when the computer decides that the session is over that sort of thing but these earlier modems don't do any of that the 103 compatible modem doesn't talk to your pc it doesn't talk to the other modem it doesn't talk or think it contains no computer at all all it has are some basic electronic components that convert logic levels into tones so at the end of the connection it doesn't do anything not until the user reaches over and switches it off this lack of intelligence is also why these modems can't dial numbers on their own there's no computer in there to receive the command from your pc to tell it to start dialing in the early days of modems you could buy something called an auto dialer which was a device you sat next to your modem your pc would tell that to dial a number it would connect the call and then hand it off to your modem to actually do the data transaction then when you were done with the call the auto dialer could disconnect it this is what made early unattended data connections possible eventually in the early 80s the haze smart modem changed all of this it added a microcontroller to the modem that you could actually have a dialogue with from your pc you could tell it to place a call you could tell it the parameters of the call such as the speed and features that you wanted you could even save speed dial numbers straight into the modem these were very popular they got cloned by every other manufacturer right away but of course they cost quite a bit more i'm sure some number of users had auto dialers and eventually everyone would have smart modems but prior to the internet for which threater bod just wasn't fast enough i think that these guys with their fully manual dialing and handshaking process were probably pretty much the norm nonetheless the simplicity of these modems is why they persisted for such a long time and why they continue to have a role in the modern world their sheer stupidity means that they aren't very hard to build they're not complex to configure and there's very little to go wrong there are 103 compatible modems that work over radio for instance both amateur and commercial the canadian institute for national measurement standards operates an am radio station which transmits the time in bell 103 format throughout the day for anyone who wants to build a device that needs the correct time but doesn't have access to the internet or an atomic clock or anything like that there's no particularly special modulation or encoding so all you need is a serial port frequency discriminator and an am radio and you're good to go in addition to being simple to implement the 103 signal is also extremely robust consider that if it can successfully demodulate the signal with the handset six inches above the receiver and a whole bunch of background noise then the signal must be pretty much bulletproof and it is the tape i played earlier started life as a wave file i generated on my pc i put it on my smartphone played it back over its little tiny speaker into the little tiny mic on the tape recorder and then played back over its speaker into the acoustic modem so the fact it made it they're intact at all is pretty astonishing but in fact i think it came through pretty much perfectly but even without the extreme disadvantage of acoustic transmission this simplicity can save you in a lot of other situations sometimes a business needs to communicate between computer systems and all they have is a nearly unusable telephone line suppose you're a paper mill in rural ohio and you have process control equipment that needs to phone home to your headquarters in another state well the only phone line you're likely to have is one that hasn't been maintained in nearly a century or possibly longer maybe it's drooping through a pond maybe it's been pecked at by birds and there's no insulation on the wires maybe when you pick up the phone and listen to this line it sounds like a power substation that's also a wind tunnel if you try and put dsl over that no way 56k not likely 14 4 maybe but you might not even be able to get a 4800 modem to run over it i mean some phone lines are truly atrocious but if you put a bell 103 on either end of that line you'll get a message through it won't be much on the worst lines you might have to resend your data over and over and over before it gets through and you might only get a one byte per second effective throughput but that bite could save someone's life fire alarm systems for instance still implement the bell 103 modulation because in the worst case scenario where that awful phone line is the only working connection to the outside world the one bite that gets through might mean send help this is i think an example of how a marker for success can be the sheer stupidity of a solution when every other option requires a bunch of front loaded effort and expertise and expense the one you can make with duct tape and baling wire is the one you're going to see used everywhere where simple success and maybe low cost are more important than style convenience and performance so the 103 was destined to be an enduring standard and it was a de facto one for about 26 years until the itu ratified it as the v.21 specification in about 1988 although v21 isn't quite the same unfortunately i lied to you a bit earlier when i said that one of these can talk to one of these i've tried it and it won't do it i think because this is expecting some kind of handshake signal that they added when they ratified it it's kind of a bummer but i have heard that some modems can do it so if you've got one you want to try or if you have one of these and want to give it a spin i'll put a phone number down in the description which you can call to get a special message let me know in the comments if you succeed even if you never experience a 300 baud connection in all its sluggish glory if you've ever used a dial up modem you've probably heard its modulation this is because if you dial up from say a 336 modem to one that can only do 14 for they don't know what their capabilities are they have to talk about it first and negotiate and the only speed that every modem knows that every other modem will speak is bell 103 at 300 baud so at the beginning of this modem handshake sequence you can hear there a couple bursts of fsk signal which are the modems discussing which speeds they support after this they will switch to a faster modulation and continue the call but at first they always start with a bell 103 so att's sophomore 1962 modem effort became an integral part of the tapestry of online computing for 20 years in the public eye and another 30 and counting in hidden corners of infrastructure and mission critical systems that most people don't even know exist it's a critical part of the history of computer communications and anyone who's ever used a modem ought to know about it and now you do that's all i have to say about it though if you enjoyed this please subscribe so i know you like this sort of thing turn the notifications on to see my future videos youtube's really bad about showing them to people and if you really liked this consider subscribing to my patreon because it cost me a lot of money to get all these modems to the people already supporting me i couldn't thank you enough here's the names of some of the people who are really showing their faith in me but i couldn't do this without all of you thank you again and thank you to everybody else for watching

Channel: Cathode Ray Dude

Views: 103,578

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Id: OmBLsKV7Sx0

Length: 29min 54sec (1794 seconds)

Published: Sat Jun 26 2021