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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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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!
Yeah, US ISDN speeds really were (are?) lower, due to RBS compensating for bad signal quality.
See here for details.
Heck, I was using "56K" dialup until earlier this year. Even though it was 33,600. For most things I was doing, it was plenty fast enough. Only thing that killed it was OS X software updates, and the occasional twit who forgot that email is a *text* medium.
Brett
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.
One of the better innovations with modems, but one that was not heralded much was MNP3. MNP5 is a superset and offered compression which helped things, but MNP3 dealt away with the aggravation of line noise, and this by itself made a lot of difference in file transfers.
ISDN did dent modem sales, but at the time in the mid 1990s, ISDN was fairly expensive (about $150-$300 a month.) However, it had the advantage of very low latency. Modems (and mom/pop ISPs) really didn't die off until cable and DSL connections became both widespread and decently inexpensive.
Ironically in the US, modems have not been driven away completely. There are still plenty of areas that do not have cable or DSL access. Sometimes using a cellular "modem" [1] provides a solution, but sometimes that doesn't work (especially in hilly areas). Also, some people just don't do much with broadband, so they have downgraded to dialup because it is cheap.
[1]: Technically it isn't a modem, but a CSU/DSU. However, most people call the USB devices that plug into a laptop modems, even though they do no analog modulation or demodulation.
Very well said. But you forgot about 14400 and 19200. Man, I sure was in heaven Christmas morning of 1992 or 1993 when I opened my Zoom 14.4k modem. Naturally it amazed me, and I thought there would never be anything much faster, aside from the "exotic" 19.2k modems that none of the local boards or my friends had. I think Zyxel and a USR model or two would do 16.8k. 1200 and 2400 were never acceptable again, though 14.4k meant speed to spare! Then a year or two later we thought 28.8k was near a theoretical speed limit for twisted-pair copper, 33.6k used dirty tricks, 56k was unrealistic and not possible for a BBS, 64k/128k ISDN was crazy expensive, and ADSL and SDSL were futuristic 21st century vaporware. Today's DSL and cable speeds were unfathomable 15 years ago, not to mention optical fiber which seems to be getting rolled out everywhere except where I live.
This is a hacked account, for which the owner can not be held responsible.
I must be getting old. I still think in terms of, "acoustic couplers... 6502's... that was a few years ago." Doesn't seem that long ago really. Now maybe most people reading this weren't *born* yet at the time.
Soon enough though folks like us will die off, and there will be a generation which has always been connected - nonstop, rather than having to dial things up, doesn't remember the mainframe days, and thinks a 386 is an old CPU. I suppose it's the way of things. Doesn't make me feel any younger though! But what certainly seems true is that a much lower percentage of people now know the nuts and bolts of how things work. I attribute this to several things:
(1) It's harder to *get at* the nuts an bolts now- there are far more layers of abstraction in the way.
(2) Back in the 70's and much of the 80's, home computers were owned by hobbyists, not Joe Sixpack, so most people involved were inclined towards curiosity about how shit worked. Now there still some - more on an absolute scale, but fewer percentage wise.
(3) Now it's possible to use a computer without knowing anything theoretical. Back then, it was not, so it was required that people were technical.
It's not a bad thing generally, and I'm glad so much of humanity is now connected, but there *was* something lost as well (Eternal September, loss of the original net culture, spam, widespread abuse of various protocols, a trend towards a computing monoculture...).
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.
Ahh, and not only exciting, but would only later be known as 'epic'. My first foray into the internet was on our school library's VT100 terminals which were primarily used for queuing up inter-library loan requests. This was in 1995. Getting Mortal Kombat cheat codes and fatalities was never so easy. I also remember printing off the Duke Nukem 3D build editor docs on that same machine, but I think that was a bit later on. Shortly after my church confirmation class took a trip to a ''church'' college which had machines which displayed the WWW in all its graphical glory. They were running Netscape (probably 2.0 or 3.0, I didn't bother to check at the time). I was smitten. Not long after that, our town got local dialup access, and at age 15 I convinced my mom to let me pay for and install a second phone line for it. I soon learned enough HTML and Javascript to 'hack' the Perl/CGI chat room I used to fool around in -- giving myself full administrative ability. W00t! The coolest damned thing I ever did was play my chatroom buddy in Quake II -- ON THE INTERNET!
To this day, there is nothing more exciting than hearing that 14.4 modem chirp off the connection sequence. Sometimes I kinda wish my DSL connection made that same noise. I'll always treasure those halcyon days. Thank you, Mr. modem inventors. Mine served me well far longer than it should have, mostly reliably, and is the singlemost important reason I ever became a computer geek. Thanks a million! Now who is calling me at five in the morn--
-AT++[NO CARRIER]
What could possibly hurt the security of the American people more than giving our own government the ability to hide its
It's not just computers, it's practically everything technological. When I was in high school in the '70s the vast majority of people who weren't swimming in money worked on our own cars, installed our own stereos, hooked up our own telephones, fixed our own appliances.
For that matter, I guess it's more than just technology. Almost none of the kids graduating with my nephew know how to fix a leaking faucet, grow a tomato, or change the oil in their car. Hell, two thirds of them can't even cook rice.
I can't help but feel that we've lost something valuable.
"Think about how stupid the average person is. Now, realise that half of them are dumber than that." - George Carlin