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posted by martyb on Monday November 20, @11:02PM   Printer-friendly
from the good-question dept.

https://www.10stripe.com/articles/why-is-56k-the-fastest-dialup-modem-speed.php

If you've ever had dialup internet service, or still do, or just know someone that does, you have probably heard terms like "56k modem". "56k" has become almost synonymous with dialup Internet access. But it's such an arbitrary number. It's not divisible by ten, it's not a power of two... so why was it chosen as the fastest dialup speed? For the answer, we will have to travel back in time quite a while.

Our visitors from Google should be warned that this is not a "stripped down" explanation; it is intended for relatively technical readers. But if you really want to know where this magic number comes from, you need to understand some of the technical background. As we shall see, "56k" was not just pulled out of a hat.

[...] Anyone that has ever used a dialup modem knows full well that they don't actually get to connect at that speed, though. And that their connection speed varies each time they dial in. There are two factors at work here.

The first is the FCC. If you are in the United States, the FCC places a restriction on the power output of devices connected to the phone network. The result is that you will never be able to connect at a speed faster than 53.3 kbit/s.

The second is the overall complexity of the phone network. 56 kbit/s (or 53.3 kbit/s) requires very good operating conditions, as it is really operating beyond the paramaters of what the phone network is required to be capable of. Operating at these speeds requires that there only be one ADC between the user and their ISP (which is not guaranteed to be true, but typically is), and that the copper wiring in the user's "local loop" have very good electrical properties. Part of the dialup process that is used to initiate a connection is an evaluation of the overall quality of the connection; if it is determined to be lacking, the modem will automatically drop down to a lower data rate.


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  • (Score: 2) by Reziac on Tuesday November 21, @04:43AM

    by Reziac (2489) on Tuesday November 21, @04:43AM (#1333694) Homepage

    Yeah, I have no idea what I was dialing into -- for the ISP, whatever was on Earthlink's end, but it was probably the latest and greatest. However, I got the same speed dialing into the more modern BBSs... so that would have still depended on the phone line, right? (Some of the little hole-in-the-wall BBSs didn't max out the old 14.4.)

    I may dig up a couple modems and see if I can get them to talk, just for shits and giggles. The things we do for science... :) Not something I ever had reason to do. Perhaps nothing any sane man has reason to do. :O

    The phone line where I got the shit speeds was some hideous routing. It had a giant loop that went several miles out of the way (per the guy at GTE, er, Verizon who tried in vain to fix it). WAAAAY out of range for even the poorest DSL. Eventually was able to get fixed wireless, but it maxed out at 1.5Mbps, cut out under anything less than perfect conditions, and after a couple years decided it could only do 300k (I stopped paying, it kept working at that unspeed, I guess everyone was happy??)

    In the present, my rural DSL supposedly can do 7 unstable, was doing 5.125 very stable for several years, but a year ago dropped to a spotty 3 with lots of dropout (which given today's web bloat, is slower than dialup was in its heyday) and no amount of complaining or resets by the tech fixes it for very long. "It's all working" but something died somewhere. Think it's gonna be back to fixed wireless, tho hopefully with better results this time.

    --
    And there is no Alkibiades to come back and save us from ourselves.
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