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A Brief History of Modems
Ant points out this two-page TechRadar article about the history of modems; the photographs of some behemoth old modems might give you new respect for just how much is packed into modern wireless devices.
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how much I miss my original mod [NO CARRIER]
512 MB RAM, 20 GB disk, 200 GB transfer, five datacenters. $19.95/month.
There are still a few of us left who grew up in the acoustic coupler era, where modems connected to the (back then standardized) handset, and really whistled and purred into the microphone.
Speeds? We started with 110 baud (which back then was equivalent to bits-per-second, if you subtracted stop bits). Then came 300 baud.
Then someone had an epiphany, and figured out that no-one could possibly type faster than 75 characters per second, and even if they could, the printer(!) that spit out whatever you typed wouldn't be able to. So by reserving the low frequencies for upstream data and the high frequencies for downstream, you could achieve the blazing speed of 1200 baud down and 75 baud up. The 1200/75 modem was a workhorse for a long time, with way faster downloads than 300/300 could give.
Then came 1200/1200, 2400/2400, 4800 (which was really 2400 with compression), 9600, and then the Trailblazer, which was running at a ridiculously low baud rate (100 baud IIRC), but at so many parallel channels that it achieved ~18000 bps aggregate. That was lightning fast! Imagine almost 2 kB/s (unless something moved the other way at the same time, in which case speeds of course would drop). The ASCII porn didn't stand a chance against that speed monster!
Then came the short-lived 38400, and finally the ubiquitous 56k modem. Yawn.
In the mid-90s, we got BRI (ISDN, 2*64 kbps in most of the world, 2*56 kbps in the US). Which pretty much ended the modem era, except for in the US and UK, where 56 kbps POTS modems reigned supreme until well after the millennium.
I have mod points to burn but I have to post in here.
The traffic system I worked on had 300 baud modems attached to cheap leased lines (soldered in, mostly). Two modems per card. 8 cards on a bytecraft backplane. Up to 128 modems on a 19 inch rack. Each modem had three LEDs (carrier, TX, RX) and at the speed the system operated you could see the poll/response from the regional controller to the sites and back. In the dark it was a thing of beauty. Computers of old.
If something was wrong in the logic (say a checksum mismatch) then you could see it in the LEDs because one channel (slot) would not follow the nice pulse sequence. Several times I mucked up the checksums of a rack and took out a lot of sites. Maybe I shouldn't post about that...
Going back in time my 6502 system had a modem for the cassette interface. I knew you could overclock the UART and FSK modem driver and I had dreams of using my uncles reel to reel hifi system for storage. Never happened. Though I did find that you could use the cassette player as a sound card of sorts by locking on REC and PLAY.
http://michaelsmith.id.au
In "The African Queen," Katherine Hepburn's character asks Humphrey Bogart's character to make a torpedo. Bogart's character says something to the effect that "Lady, there ain't nothing so complicated as the inside of a torpedo. It's got gyroscopes, compressed air chambers, compensating cylinders..."
I remember once reading details about just how the signals in a 1200 bps modem worked... and modems at higher rates. It was just jaw-dropping how sophisticated it was. The reason why there was a distinction between "bps" and "baud" is that "baud" refers to the number of times per second the signal changes. Well, a 1200 bps modem only changes its signal 600 times a second... but it uses four different combinations of frequency and phase, so each signal combination signals two bits. That's bad enough, but the combinations literally increase exponentially. The 9600 bps modem actually requires the receiver to sense and distinguish sixteen different analog combinations (so that it can encode four bits at a time).
At the time I figured they had to be close to the theoretical limit, which depends on the bandwidth and the noise level. A phone line is only good up to about 3000 Hz. so the 2400 baud rate of a 9600 bps modem is changing about as fast as it can. The rest depends on how noisy the line is.
Theoretically, of course, you can signal at an infinite rate on a perfectly noise-free channel. Just send 3.141592653 volts on the end and measure it with a ten-digit digital voltmeter and, voila! You're sending ten digits at once. Except there aren't any ten-digit voltmeters.
I was frankly flabbergasted when they managed to cram 56 kilobits per second into a phone line. Of course, the 56 kb modems never really ran at that speed--they were always falling back to lower speeds because the phone lines were too noisy. Then they added compression, which didn't do much good because the ZIP files and JPGs you were sending were already compressed. In reality they were trying to cram 56 kilobits of data into a 33 kilobit bag, but it was amazing that it even worked some of the time.
But, lady, there ain't nothin' so complicated as the inside of a modem.
"How to Do Nothing," kids activities, back in print!
The biggest problem with using modems was that you had to let everyone in the house know you were on the "modem". This meant, sticking post-it notes to every phone in the house, so that someone would tell you they needed to use the phone rather than just picking up the phone and dialing. You also couldn't tie up the phone for hours on end. There was very very few people that had an answering service (not an answering machine), like most do today with VOIP or CableCompany Provided Voice.
You also had to remember, if you were one of those people that had it, disable call waiting, as many modems would drop the connection when a call waiting signal came through. I believe you had to add a *70 after the AT.. so you had something like:
Today people can spend all day actively or passively (by leaving the computer on) online. Wit
Otherwise how could you think that v.32bis (14.4k) was introduced in 1980? I had to look it up to see what the hell they were on about, apparently the 1980 figure comes from a break through channel coding paper written in 1980 at IBM that didn't even get passed around for a few years. The reality is that the public had to wait nearly a decade before those techniques were out of the lab, and a few more years before a standard was ratified. Trying to figure out what niche this article fills - the wiki article on modems does a far better job at going over the same info. Hell, the author of TFA even put an old-time(tm) bw filter on a photo from the late 80s trying to make it seem like a shot with a laptop came from the 60s.
This should be the brief history of the personal PC modem.
There was no mention of the tons of ISDN modems used until the late 90s.
No mention of Codex or Pairgain devices. We had 64kbps, leased-line Codex modems humming along until, well, even today you'll find an odd one laying around. And T-1 Pairgains (not technically models) are still the best way to service outlying buildings on most campuses.
I understand that not every article can be complete. But you really can't talk about the history of modems without Pairgain (now ADC) and Codex.
I'd rather you do it wrong, than for me to have to do it at all.
It's sad that only commercial modems are mentioned.
I well remember building a series of homemade modems starting in the early '80s.
There were many magazine articles for homebrew modems. Most of these derived from the FSK radio modems in widespread use by Hams at the time.
No MODEM using the standards indicated has worked at any speed greater than 2400 baud. (That means 2400 transitions per second).
Many MODEMs work at 4800, 9600, 14400, 56000 bps (bits per second, or pieces of digital information per second).
What the MODEMs have done is use the ability to deliver multiple bits per such transition using FSK, QFSK,QAM, etc.
MODEMs at 2400baud or less did not require flow control -- they worked at serial line speed, and did not buffer. Modems at 4800bps and higher did buffering and would do various flow-control techniques.
Original MODEMs didn't start at 150baud, they started at 75baud, but lazy authors write lazy articles.
The acoustic-coupler worked great at 300baud (TI Silent 700), miserably at 600baud, and terribly at 1200baud.
Still this technology made itself obsolete. People were tying up VOICE channels on the PSTN switches and Telcos hated it, so they created DSL to take data off the voice channels.
E
P.S. The word MODEM (as the article indicates) represents MOdulatorDEModulator. Hence it should be capitalized. This is also try of enCOderDECoder (CODEC). Slightly less related yet as correct LASER and RADAR....
In the 70's, a number of ppl still had party lines. Basically, could not use it. Those that did not have party lines had very dirty lines. My modem ran normally at ~75 baud, though it was rated at 150. The reason was simply due to the lines. If you ran at 150, the chars would get bad. And while there was a parity bit, it really did not do the job. So, you ran slower and slower speeds. Also, it was possible (in fact, probable) to have your connnection cut. This was all in Northern Ill (the largest close town was a whopping 15K ppl; McHenry, Ill). Once I moved to Ft. Collins (ft. fun), Colorado, the lines improved in the town. We ran 150 and some places could run 300 baud. Outside, of the town, it was still party lines.
I prefer the "u" in honour as it seems to be missing these days.
Thanks for that. :)
Just reading http://en.wikipedia.org/wiki/Novation_CAT
Neat use of transfer bandwidth ideas
Domestic spying is now "Benign Information Gathering"
A few friends and I were talking about our days on dialup when we were growing up. One friend was commenting on not noticing the download time on a 5 meg file, and how he complains when his download speeds are 500 k per second now. We had a little fun recalling our top-out speeds of 4.6 k per second, and the magical "1 meg every six minutes" rate we had all calculated growing up.
We all agreed that in a way, it is almost a shame that kids today are growing up with remarkably better technology than we had at their age (and it hasn't been that long ago that we were their age). We all sort of miss dealing with cobbled together and salvaged parts, trying to eek out any performance we could from our machines. One of the friends present recalled helping me overclock my 33 mhz machine to 36 mhz (woohooo! A 10% gain) and how excited we were.
These days, my cell phone has more computing power than the first three computers that I owned, and a much faster data transfer rate. The old technology still amuses me though.
Randimal: AT-CG-CG-AT-CG-AT-AT-CG-CG-AT-AT-CG-AT-CG-CG-AT-CG-AT-AT-CG-AT-CG-CG-AT-AT-CG-CG-AT-CG-AT-AT-CG
I just remember US Robotic modems and BBS's and when you were lucky enough to have a USR and connect to another US Robotics modem you always seemed to get a speed just above what everyone else had. (HST mode) 16.8k back in 92-93 us laughing at the poor 14.4 guys. In retrospect... kind of sad.
Its a shame that the article missed so much....
Like the times when much of the industry didn't want to license the Hetherington Patent from Hayes on the "guard time" surrounding the "+++" in the escape sequence, so Hayes ended all of their press releases with +++ATH0 (which would cause a lot of modems to hang up on the BBS systems of their day).
They also missed the interesting fact that the "56K" modem was an old idea that was rattling around Bellcore for years before 1996 and fairly common knowledge in the Bell system. [The big issue with getting there was the need to have digital trunks connecting all of the dial-in server pools with the telephone network.]
Probable never would have become a mainstream consumer device without AOL. Until AOL, you really had to be a geek to use one.
And, of course, the modem wars of 1996-1998, as the major technology companies duked it out, the vast majority of modem companies went bust, including Hayes.
After thousands of times listening to my various modems connecting from 300bps to 56K and with the various incarnations of error correction I was eventually able to knowing how fast I was connected by sound alone. The problem was that as modems got faster and more sophisticated the connection time kept getting longer and longer. Sometimes I'd have to wait through 45 seconds or more of whistles, grinds and groans before the two modem would train. Ah, the good old days.
In the vain hope that they'll have nostalgia value someday I still have in my possession:
1) Mint condition Hayes Smartmodem 2400. The original workhorse.
2) Practical Peripherals 14.4K. long box with a one-line LCD that displays the connection speed and error correction mode
3) US Robotics 56K Courier - The last great standard.
If you don't want to repeat the past, stop living in it.
I was trying to put together an inexpensive homebrew computer-to-transceiver audio interface for digital radio transmissions and needed a pair of audio frequency transformers. I knew that all POTS line modems had a transformer in them that would work and I thought that this would be a cheap source for parts that cost about ten bucks apiece new. Of course, I had just recently sent all my old modems to the recycler so I started asking around to see if anyone had a modem that they wanted to get rid of. Out of the more than 20 people I asked, not a single person still had one.
Hard to believe that only ten years ago the modem ruled supreme when it came to Internet access. Now you can't even find one to cannibalize.
KJ6BSO
This ain't rocket surgery.
Back in the early '90 the whole HST vs V32.bis was a big deal for a couple of years. It's a bit sad to not see this mentioned in terms of the impact to the PC modem world...
*** Sigs are a stupid waste of bandwidth.
While one might think things have improved by four orders of magnitude (10,000x), thanks to Parkinson's Law, they have only improved by two orders (100x). Navigating to the washingtonpost.com home page takes 7 seconds to load on my 2.5-year old 2GHz desktop with Firefox. CTRL-A and CTRL-C then paste into Notepad yields a 15K text file. 15 * 1024 * 10 bits / 7 seconds = 19.2K.
Hey, it's like I'm back running my 1992 BBS.
What history of modems completely skips the Telebit Trailblazer? Roughly 18 kbps in 1985 - many years before 14.4k modems became common. Expensive enough to be out of reach of most BBS'ers, though. But worth the money if you were doing UUCP over a long distance call every night.
I don't recall V.42 / MNP being popular with 2400 baud modems. The data rate was so slow that enabling error correction resulted in too much latency when "browsing" text. MNP could be done in software also, and a few comm programs offered it. They missed the whole Courier HST vs. v.32bis battle. The v.32 and v.32bis modems were way more expensive than USR's modems for a long time because implementing that standard required an echo canceling chip. This allowed full speed bidirectional transfers where USR's didn't. Most didn't care because they weren't usually doing both upload and download at the same time. That is, unless they were using Bimodem, which allowed two-way transfers. And you could chat with the SysOp during the transfer! Good times, good times...
Yeah here Telecom Australia charged $10000 AU dollars per year for a DDS connection (thats 9600 bits per second, serial on a 25 pin D connector, point to point). Its a good service, but 10 grand?. The early limitations on modems not provided by Telstra were basically there to protect that business.
http://michaelsmith.id.au
I once worked at a place that had a DEC/VAX mini with a bank of about 8 modems for VT100-compatible terminals. If there were modem complaints such as dial-in problems, I had to first figure out which modem was connected to which phone number. Others didn't always keep the map up-to-date. Plus, it used busy-roll-over.
The test phone was a ways away from the modem bank for the VAX minicomputer, so I had to keep the modem trying to connect long enough until I got there to see which modem answered the call (via LED). The only easy way I found to do this was to manually whistle an acceptable modem tone into the phone in order to trick the modem into thinking I was a modem trying to connect. This would keep it trying long enough to allow me to run from the test phone to the modem bank. It had to be the right pitch and wavering to work most of the time. I got pretty good at it after a while. I learned to "speak modem" a bit.
A computer-room technician once saw me whistling modem sounds into the phone and running back and forth. I later told him why, and he told me I was nuts and mumbled something about whistling sweat nothings to my robotic girlfriends.
Table-ized A.I.
This is how I remember it. Hayes modems, using the patent, required a certain amount of delay time surrounding "+++", their escape sequence, before the modem would recognize it. Thus, "+++" in the text stream wouldn't trigger it under normal circumstances because it would come and go too fast.
But the patent was a patent on the delay; and to avoid paying for the "delay" royalties, other modem companies would just use "+++" without the delay for their escape sequence, which risks modem confusion if accidentally sent as text, but otherwise wasn't that common. However, to embarrass non-patent modem companies, Hayes embedded "+++ATH0" in their digital documents. This would cause non-Hayes modems hang up if they ever transferred such documents. The trick sounds rather Microsoftian.
I remember other vendors complaining to the press, saying "you cannot patent pauses. Next they'll patent Ummm's" or something like that. (Obama would have a big bill if they did.)
Table-ized A.I.
Bah, kids nowdays, so spoiled with the megabit modems.
Before the Bell System modems, there were over-the-airwaves modems, going back to 1930 or so. The endpoints were teletype machines, whirring away furiously at 60WPM, 7.42 bits per character. ( 5 data bits, one start bit, 1.42 stop bits).
The modems wee made up of L/C filters and a trunkful of vacuum tubes. I used to have a military modem, a CVV -something, that was the size of a suitcase and weighed about 60 pounds. 42 BPS.
But it could do 42BPS over a noisy fading shortwave radio link, all day long, while taking direct mortar rounds, and never say "NO CARRIER."
I was online with many BBS' with during dial-up modems days before they died because of the Internet. /. has a few old stories about this awesome documentary from years ago:
Google Video has all the parts online:
1: Baud introduces the story of the beginning of the BBS, including interviews with Ward Christensen and Randy Suess, who used a snowstorm as an inspiration to change the world.
2: Sysops and Users introduces the stories of the people who used BBSes, and lets them tell their own stories of living in this new world.
3: Make it Pay covers the BBS industry that rose in the 1980's and grew to fantastic heights before disappearing almost overnight.
4: Fidonet covers the largest volunteer-run computer network in history, and the people who made it a joy and a political nightmare.
5: Artscene tells the rarely-heard history of the ANSI Art Scene that thrived in the BBS world, where art was currency and battles waged over nothing more than pure talent.
6: HPAC (Hacking Phreaking Anarchy Cracking) hears from some of the users of "underground" BBSes and their unique view of the world of information and computers.
7: Compression tells the story of the PKWARE/SEA legal battle of the late 1980s and how a fight that broke out over something as simple as data compression resulted in waylaid lives and lost opportunity.
8: No Carrier wishes a fond farewell to the dial-up BBS and its integration into the Internet.
There is a DVD version that can be ordered, or downloaded for free and legally (hurray for Creative Commons) with less contents.
Ant(Dude) @ Quality Foraged Links (AQFL.net) & The Ant Farm (antfarm.ma.cx / antfarm.home.dhs.org).