Their arrival heralded a new age of communications and they played a major role in the explosion of the internet. We're talking, of course, about modems. Here we look back on the development of this remarkable device.
When the US Air Force needed a convenient way of transmitting hundreds of radar images to command centres during the Cold War in the late 1940s they turned to the telephone system as a solution.
Fortunately modems, already in action in Teletype since the 1920s, were the perfect tool for taking the digital radar images and converting them into analogue transmissions and then back again so that they could be sent across the network of telephone systems already in place.
FIRST MODEM: AT&T's 1958 modem. Not exactly your small, white unobtrusive box of today, is it? [Image credit: AT&T]
The modulator-demodulator, aka the modem, was enhanced by Bell Laboratories to improve upon the Teletype speed of approximately 150 bits per second (bps).
It was in 1962 that the first commercial modem, the Bell 103, was released by AT&T. Including full-duplex transmission, frequency-shift keying (FSK) and a speed of 300 bps (baud). These modems were designed to hold a telephone's receiver in a cradle with wire connections running from the cradle to the computer.
BIT BY BIT: The Bell 103 modem that ran at 300 bits per second [Image credit: www.velocityguide.com]
To grab a bit of perspective on the actual speed of these modems, consider that a letter consists of eight bits. A speed of 300 bits meant that this modem could only send out around 30 letters a second.
It was also in the 1960s that Paul Taylor, building upon the work of James C Marsters and Robert Weitbrecht, developed the world's first telecommunications device for the deaf using an acoustic modem.
CONNECTED: The Miniprint 425 TDD telecommunications device for the deaf
The spread of bulletin board systems (BBS) meant that users were soon demanding greater speeds to transfer larger files and images and market demand led to the development of the V.22 or Bell 212 modem at 1200 baud.
ONLINE: Using a 1200 baud modem to access the BBS at one of Canada's largest universities [Image credit: dblackadder]
This modem delivered more characters and introduced a very simple data compression that worked well with text but didn't have great results with images.
Running along in the background was also some hefty legal action and competition as AT&T initially prevented customers from connecting devices from other companies to their telephone lines.
However, thanks to Tom Carter the Carterfone Decision of 1968 soon saw this unfair advantage taken away from AT&T.
"While we could visualize what should be possible and how it could change the shape of the communications industry, our first thought, however, was for self preservation... I approached a number of communications equipment manufacturers for financial support, but they were all afraid of jeopardizing current or potential Bell contracts," said Tom.
After he won the case the market was suddenly left wide open with companies like General Electric entering the field with glee.
Your comments (10) Click to add a new comment
amarsh04
December 29th 2009
10. Their were three things that stood out to me that the BBS era achieved: improvements to file compression programs (e.g. PKARC, PKZIP, ARJ), improvements to file transfer protocols (XMODEM, ZMODEM, Kermit (still in development!)) and improvements to the speed and compatiblity of modems (often at great expense to the owners of the modems). My first V.22bis (2400bps) modem cost about AUD$400 in 1989, my first and second V.34 modems cost about AUD$1700, and one still serves as a backup to a 12178 kbps down/1014 kbps up ADSL2+ service.
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linearbob
December 27th 2009
9. The reason many people stayed with their 300 baud modems as long as they did had to do with two factors: 1) how fast their printers would print (or their screens display) the incoming characters, and 2) how fast they could read.
It turns out that most people read around 300 words per minutes, and that is close to what 300 baud transmission will do with ASCII characters. So, with text based files that were read as they flowed through the modem (and not always saved because of limited storage space) 300 baud made sense, especially for people with video display terminals.
Later on, the "on line services" began to "upgrade" their modems and offer higher speed transmission, but even with 56 K baud, there still were a lot of people who continued to read at 300 words per minute, so the net data rate remained around 300 baud, but now consisting of bursts about 1 page in size. Only when files were stored on disk for reading off-line did it make sense to use a faster modem.
But as modem speeds increased, the on-line services (CompuServe and the others) began to shut down their slower modem speeds. Eventually, a 19.2 K baud (or faster) modem was required, no matter what you wanted to do. It turns out the reason for forcing people to "upgrade" to such faster modems was related to the on-line services wanting to send not ASCII characters to their customers, but they really wanted to send pixels. The whole point of the "on-line" services wanting to send pixels was ADVERTISING, and especially corporate LOGOs, which rarely survived translation into ASCII.
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cpet
December 27th 2009
8. dulac_pt why sorry if you are right?
Lesson learned here is not reading threads at 5AM when your eyes are closing shut and not reading the post properly. Reading it now yes starfleet is very right.
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garethharris
December 27th 2009
7. Sending digital data over analog sound with a modem is like using television to send smoke signals.
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dulac_pt
December 27th 2009
6. Sorry, but starfleet is wright. Very right.
Nobody would deny I'm writing in some sort of English. However it was stated the equivalent.
That I'm not writing in in ASCII instead of English.
What you say, the way you do it, the code used, the medium of expression... All are different dimensions of information. And even errors are information, though an erroneous information.
And, maybe sounding a bit pedantic, any information is always limited and thus it is erroneous, only valid in a context (also limited and erroneous - but useful).
It is up to the receiver to interpret and unite information in an higher level of context. (also limited and erroneous by an higher look). And this applies to everything in life, science, politics, religion... whatever. Just try and be amazed.
So, different things can be one thing and one can be many. It's us who force views, who err more securely as we learn but not enough. So the wise man said:
"It is wiser to know nothing than to know little"
and explained:
"Knowing little, one is convinced to know all"
Starfleet, unaware of it, answered the comments before they existed... In English, Extended-ASCII and in binary:
011101010010000001100111011001010110010101101011
Sorry by the extended comment, but felt the need for the message to pass correctly, not misinterpreted.
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grismar
December 27th 2009
5. My apologies to mfraser, since he's being neither pedantic and appears a faster poster than myself ;)
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grismar
December 27th 2009
4. Since all this thread will ever amount to is pedantry, I might as well tell you both off. Anyone can tell what starfleet wrote is binary. But to be able to interpret the number, you still need to know what code table it is using and that's ascii. So, cpet learns a little something.
However, starfleet is using something 8-bit, it seems, considering the number of digits in there and his clues to their meaning. Regular ascii only needs 7, so a misinterpretation of his text might end up as ':H v++' without that bit of info.
(Btw: this site needs a bit of a usability update. Needing all but my social security number to register and taking 5 minutes before allowing me to log me in... no wonder there's only 3(!) responses on a page that's been on freakin' Slashdot)
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mfraser
December 27th 2009
3. There 2 different 56k protocols developed at around the same time K56flex and X2 later becoming v90. I remember being able to reflash my Pace modem after v90 became standard.
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cpet
December 27th 2009
2. dont confuse ascii with binary.
Asa121a = Ascii
010101000011 = Binary
2 different things.
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starfleet
December 26th 2009
1. By the way:
011101010010000001100111 011001010110010101101011
Means "u geek" in ascii
Just in case anyone is interested
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