LanTimes article on DSL
This paragraph or few bugs me:
But for all of xDSL's appeal, network and IS managers
would do well to approach this new technology carefully,
because deployment raises a number of issues.
One of them--the state of the local loop--is proving to be less
of a problem than many observers had anticipated. But that
will be little consolation if you launch an installation effort
only to discover that the copper wiring into your facility won't
support it.
That unpleasant surprise can happen. "In reality, you never
know if ADSL will work until you install it," says Rob
Brading, marketing director at Atlantech Technologies Ltd.,
an xDSL management-systems vendor based in
Cumbernauld, Scotland, and Westborough, Mass. "There is
really no way of testing it; the best piece of test equipment is
actually the ADSL equipment itself."
The line must be unloaded, without any load coils or bridge
taps. Gauge mismatches--24 gauge in the feeder and 26
gauge in the main trunk, for example--can cause
discontinuities and reflection, slowing throughput.
The key variable, though, is the length of the loop. Copper in
perfect condition will support 1.5Mbps ADSL over distances
of up to 18,000 feet and HDSL over 12,000 feet. But few
installed copper loops are in perfect condition, and in some
cases the telco records may be in worse shape than the
copper.
uworld.com
Derek |
