Text 311, 88 rader
Skriven 2004-08-03 13:47:00 av Michiel van der Vlist (2:280/5555)
    Kommentar till text 299 av Peter Knapper (3:772/1.0)
Ärende: Fido on the move via cell phone.
========================================
Hello Peter,

 >  > 1:  POTS lines can work while longer and thinner than ISDN lines.
 >
 >  MvdV> Are you sure you are not confused with ADSL?
 >
 > It all comes down to the frequencies used for the
 > signalling over the cable. POTS uses the lowest
 > frequencies, so can travel further (less signal loss). ISDN
 > frequencies are higher than POTS so can't travel quite as
 > far. ADSL uses even higher frequencies so has less distance
 > capability than ISDN. The higher the frequency spectrum
 > required, the greater the loss and hence the less range the
 > signal has over the same copper cable (among other factors
 > such as cross-talk between adjacent cables).

All true. can't argue with the theory. But how does it work out in practise.
Thing is, I have found limits for ADSL ranging form 2 to 8 km, but I can't find
range limits for ISDN everywhere. That suggests it is not a problem in
practise.

Maybe I did not search hard enough.

Keep in mind also that ISDN by its digital puts a lower demand on the Signal to
Noise ratio of the line than analog signals.

 > The biggest problem with signaling such as ADSL is at the
 > exchange where all the copper cables come close together, they
 > They have a really hard time stoping the signals from
 > interfereing with each other...

Indeed. But that is ADSL...

 >  MvdV> Even if you are right, it does not apply if I
 >  MvdV> correctly understood Carol. She was referring to the

 >  MvdV> wiring in the apartment building wasn't she? Surely
 >  MvdV> that short stretch can't make the difference?

 > > 2:  Cables can not carry more than a certain number of ISDN
 > > lines; don't ask me how many, I know that the limit exists.

 >  MvdV> Again: are you sure you are not confused with ADSL?

 > No, the signal loss and interference issues affects all
 > transmission types over copper lines.

Again: in theory. How is it in practise?

 > > 3:  If the NT must be installed someware downstaires, you
 > > need 4 lines instad of two and that might indeed mean quite
 > > some wiring thru hidden ducts...

 >  MvdV> I can't think of any reason at all why the NT /must/

 >  MvdV> be istalled downstairs.

 > The main reason I can see here is that perhaps there is a
 > recognised demarcation point between the service provider
 > and building owner, and that is located "downstairs".

That sounds like on of the typical excuses our telecom used to come up with
when the still had the monopoly and they did not want to tell you the real
reason why they did not want to provide a service.

I have heard lots of these "stories". Bob Bashe has also made some interseting
observations on the behaviour of monopolists.

I myself had to wait over 6 month for a telphone when I move from the north of
the country to the place where I now live. The resaon they gave was that "the
exchange had run out of numbers". I knew that to be a flat lie. The real reason
was that they were short of pairs in the cable in the street and they did not
want to dig up the street to lay a new cable for just one customer. When six
month later someone in the street moved out, the exchange magilcally had unrun
out of numbers and I got my phone,

That was 25 years ago when Dutch Telecom was the only game in town. Now that
there is competion they guarantee a phone within four working days. Exchanges
never run out of numbers any more and if they have to dig up the street to lay
a new cable that is what they do. Here the "stories" are over.

If I understand Carol correctly in Japan telephony is still a monopoly. So one
can still expect to be told "stories" there...

Cheers, Michiel

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