Re: DSL Speed

Choreboy wrote:

>> It seems to me that dialup and DSL would be analagous to two ways of >> yelling across a field; like two ways of yelling, DSL and dialup use >> the same medium. > A very simple analogy might be yelling, then using a megaphone > to yell. The megaphone doesn't "amplify" your voice, but directs > it a little better so it can be heard further.

Couldn't technology analogous to a megaphone be applied to dialup as well as DSL?

Adding this analogy, imagine yelling across a field crowded with > people talking as opposed yelling across an empty field. The speech > of the other people will interfere with your yelling.

Ah, crosstalk! It seems to me that if DSL uses the same wire dialup used, the same crosstalk will be present.

Another analogy might be signalling across a field using colored > flags. In all cases you are using reflected light. But the ability > to see the distant flag will vary based on the color of the flag. A > person holding a green flag standing in front of trees will be > difficult to discern compared to someone holding an orange flag. The > _carrier_ of your signal--the reflected color of the flag, is > different and different carriers are more efficient.

I'm interested in how the DSL signal is different.

Let's note that the limitation isn't just in the plain copper wire > that comes out of your telephone.

On dialup, it seemed to be the wire that wouldn't let me connect at the farm at the same speed I could connect a block from the CO. I wonder how the farm wire, that wouldn't take 50k on dialup, will carry

1.5M or more on DSL.

There's also a limitation in the

> telephone company facilities. A voice conversation doesn't need much > "room" (bandwidth) to be clearly understood.

I have trouble understanding on the phone, and I often resort to the phonetic alphabet to be understood. I think the problem may be more in the typical quality of phones than in bandwidth. Who don't phone manufacturers list frequency response, distortion, and sensitivity for speaking and listening? A control to match the telephone's impedence to the line impedence at your location might also help.

(Notice if you play music over a telephone that sounds terrible at > the other end -- that's because the phone doesn't have the bandwidth > for the more complex sounds of music compared to voice).

With better fidelity I might know for sure which family member answered the phone.

Anyway, the telephone company has your voice share space with other > voices. While this is fine for voice, it limits data transmission > to 56K.

Does a POTS line from the CO to a house carry multiple voices? Anyway, DSL at the farm uses the same line that the phones at the farm still use.

Between the CO and the customer, isn't voice service just bare wire? > Are there inline amps? If so, they could preemphasize high > frequencies. That varies tremendously from customer to customer.

If there are inline amps, preemphasis could be set according to the length of wire between the customer and the CO.

> I don't understand what kind of signal dsl uses to carry so much more >> data than dialup without needing broadband cable. > It uses digital. Crisp, to the point. As mentioned above, an orange > flag transmits 'better' than a green flag. Both are using the same > medium. Digital transmits better and can make better use of a pair of > wires.

Digital is clear because the receiver need recognize only two states. Marconi invented the digital (telegraphic) radio transmitter in 1895. In 1979, ships were still required to have telegraph operators because nothing could match Marconi's radio for range and clarity.

The data stream was slow. FSK allowed a faster data stream (between teletype machines), but it operated at a higher frequency, which reduced range, and with a wider bandwidth, which made it less clear and reliable.

Satellites made Marconi's radio obsolete at sea. I understand satellite channels offer wide bandwidths, which have room for fast data streams. If at the farm I can download 1.5 Mb/s, it sounds as if those miles of POTS telephone wire have a bigger bandwidth than I'd thought.

> If you have a second phone line for your modem, a $25 ISP, Direct TV, >> and perhaps other Bellsouth services, they will give you a price where >> going to DSL will lower your costs. However, for somebody whose only >> cost is $100 a year for an ISP, DSL would add $500 to his annual >> budget. Many feel they can't afford it, just as farmers before the >> Model T felt that they had no choice but to stick with slow, >> inconvenient horses and wagons. > AFAIK, if you get DSL, you no longer need a second phone line and > everything can come over your DSL line. That is, you can talk on the > phone and use the computer at the same time, and get faster computer > response.

The same POTS wires feed all devices including the DSL modem. You plug in phones, answering machines, and dialup modems through inline filters. Bellsouth says the filters protect the conventional devices from high frequencies. I think the filters also keep those high frequencies from draining through those devices.

Besides using a DSL computer and a phone at the same time, you can use two or more computers with DSL modems at the same time. That surprises me because I think all computers on the same DSL line are assigned the same IP.

The pricing of services is a function of marketing, not technology. > A consumer has to choose the best price/service suited to their needs. > Sometimes a bundled package may end up still cheaper than a la carte.

A bundle can be cheaper if you would have bought all the services anyway. For marketing, bundling can entice a customer who would not otherwise have bought them all. You lose the customer who wnats just one and doesn't have money to waste. That's why Henry Ford didn't bundle his cars with garages.

> You say internet costs depend on how much traffic you have. > That's not really accurate. Internet costs whatever you want it to > cost.

I was speaking of Bellsouth's costs. I understood million-dollar switches were the big cost for voice service, while equipment to carry heavy internet traffic was the big cost for DSL.

If need your response RIGHT NOW, you should get a higher speed > connection. If you're doing a lot of work and don't like the long > waits, you should get a higher speed connection. If you don't mind > slow response time, you can make do as is. Plenty of people do. > There are even higher speed connections than DSL, although at some > point you're limited by the overall Internet traffic and the response > time of remote sites.

I'm talking about another possibility. For example, sometimes I go to to NWS to download ten radar images showing the progression of any storms in the area over the last hour. Suppose they total 10 Mb (1MB).


12 minutes at 14.4kb 6 minutes at 28.8 4 minutes at 40 3 minutes at 50 1 minute at 150kb 7 seconds at 1.5 Mb

12 minutes for 1 MB shows why not many people surf at 14.4. I never want to go back to 28.8, which would take 6 minutes instead of 3.

If DSL let me download those images at let me download at 1.5Mb/s, I could save another 173 seconds. If I contracted for DSL that would deliver only 10% of that speed, I would still save 120 seconds compared to 56k.

Indeed, often times what appears as slow > connections is actually not related to your own connection, but at > intermediate or distant ends.

That's another reason DSL with a limited speed would be interesting.

> I think there's a big untapped market for DSL, and it could be >> profitable at a low price. Cadillac did not introduce the Model T, >> and I guess Bellsouth doesn't want to offer existing customers >> something cheaper. > What is being offered is changing rapidly as technologies change and > new equipment is installed. Many cable companies offer service over > their lines as well in competition with Bell companies. Some Bell > companies are offering "FIOS" which is extra high speed. > Some of us whose modems keep getting fried by lightning are making > do with 14.4.

That happened to me with a 14.4 modem before I discovered that my phone ground and power ground hadn't been bonded. Is a 14.4 modem more lightning proof than a 56k?

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