TELECOM Digest OnLine - Sorted: Re: DSL Speed

Re: DSL Speed

Choreboy (
Fri, 24 Jun 2005 12:10:26 -0400 wrote:

> Choreboy wrote:

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

> Not necessarily. Remember AM and FM radio waves go through the same
> air, but AM is much more sensitive to lightning and other static than
> is FM.

By your analogy comparing a noisy room to a quiet one, I thought you
meant the wiring for DSL had no crosstalk.

> DSL service may be arranged to minimize crosstalk.

So there's less crosstalk on wiring used for DSL?

>> 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.

> Because it's NOT just the wire to the farm, but ALSO other parts of
> the telephone plant being set up for DSL.

At the farm, it seems to be the wire that limited my dialups to 46k
when I got 52k in town. If the wire wouldn't carry more than 46k, it
wouldn't matter what the telco did at their end. I wonder how a DSL
signal can carry 1.5M through those mile of wire.

>> 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. You could
>> have broadcast quality microphones and loudspeakers and it will
>> still sound like a telephone because of the limited bandwidth.
>> Since bandwidth is limited, telephone components aren't high
>> fidelity as it would be a waste to make them so. (I believe the
>> modern "K" handset is clearer than the older "G" handset.)

Military AM and SSB are limited to 300-3000 Hz. Shortwave radios can
be filtered that way for tuning and difficult conditions. Speach
comes across pretty clearly. If telephone voices are harder to
understand, I think the problem must be something besides the nominal
bandwidth of a telephone.

>> Does a POTS line from the CO to a house carry multiple voices?

> Depending on the location, often times yes. Between central offices
> or within the CO almost always yes. I mean if you live across the
> street from the CO you probably have dedicated copper pair, but you
> live some distance you probably are multiplexed over a carrier line.
> The degree of multiplex determines your bandwidth.

Would you be able to connect with V90 on a multiplexed line?

>> 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.

> Remember that while Henry Ford did very well at first, eventually
> General Motors and Chrysler surpassed him with their cars. They
> couldn't be the Model T on price, but they had better marketing. What
> was great in 1918 wasn't so great in 1928. Henry Ford was so stubborn
> he almost ruined the company and his family had to take it away from
> him. Even his wife voted her shares with the others and he was forced
> out. It's a shame such a brilliant man was also such an mean SOB.
> His "$5/day" wages was partly myth.

I think it was speed and price. Roads had improved by 1928, and other
brands were faster than the Model T. I suppose the competition was
also more affordable than it had been in 1908. Similarly, consumers
who once settled for 14.4 modems now want faster speeds, depending on
the price.

>> 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.

> In many cases, if not all, the equipment is the same. Today voice
> talk is converted to digital for transmission, and those digital
> signals share the lines with DSL signals. I'd say the biggest
> investment (beyond more capacity) was in local loops so that customers
> could have reasonable speed on DSL. Not everyone can get it.

Earlier in the thread I learned that the switches for voice calls are
very expensive.

As far as capacity goes, I don't know how fast is the digital stream
for a voice call, but I'm sure DSL at 2.5Mb/s requires much more of
the telco's capacity.

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