Re: ISDN question

[jwb@example.com (Jim Breen)]

>> From: Yamagata Hiroo <hiyori13@example.com>
>> 
>> ISDN itself is getting a bad name these days.  xDSL people in Japan complains
>> that ISDN signals interfere with xDSL signals and "pollutes" the lines.
>> 
>> At least in Japan.  Not much to do with Linux, but does anyone know if this 
>> is also the case in other parts of the world?

This brings a smile to my wrinkled visage.

It's called "cross-talk", and it's only been around for about 160 years.
It's something that the deregulators, with their degrees in law and
economics, know nothing about. Of course if you put big fat
high-frequency signals down telephone wires they'll radiate like fury
and all the other cables in the bundle will act like antennas and pick
it up. It the days when we ran a lot G.732 1.5/2.0Mbps stuff over
telephone pairs, the rule was only one circuit for each bundle of 50
pairs.

Dunno about xDSL, because there are a lot of cowboy systems out there,
but the original ADSL was fairly carefully designed to stay right away
from the signals put out by typical ISDN signals. "Typical" is a bit
vague, because different countries supply their 2B+D services in
different ways, but usually it's a self-clocking baseband running about
200kHz.

Having xDSLs coexisting on cable sets it always asking for trouble. One
of the reasons ADSL/xDSL is slow getting going in Australia is that
since the main cable plant owner (Telstra) is now required to open its
cable up to competing xDSL services, the Aus. Communication Authority
is forcing the suppliers and would-be carriers to develop and agree on
an industry standard for compatible xDSL systems, so that there isn't a
welter of litigation from people "polluting" each other in adjacent
cables.

Back to work.

Jim
-- 
Jim Breen  [jwb@example.com  http://www.csse.monash.edu.au/~jwb/]
Visiting Professor, Institute for the Study of Languages and Cultures of 
Asia and Africa, Tokyo University of Foreign Studies, Japan
+81 3 5974 3880         [$B%8%`!&%V%j!<%s(B@$BEl5~30Bg(B]