1) The Nokia DSLAMs used by Telecom until last year do work this way to an
extent - the intelligence is centralised and dumb bins full of line cards
(basically multiple DSL modems) distributed to local exchanges. However, the
main cost of a DSLAM is actually those line cards, so the saving isn't
great. Other "brands" of DSLAM, such as Telecom's newer Alcatel equipment,
don't bother with this complication and allow each node to be completely
independent.
DSL repeaters do exist but they are expensive - effectively two line cards
back-to-back, so they only get used in a few specialised situations.

2) As connect quality is determined by the total length of cable in the
circuit, adding extra copper of any quality will only slow things down.

3) Urban exchanges cover smaller areas but use thinner copper to do so. The
net result is that all exchanges designed to be OK for telephony to their
boundaries, tend to get dodgy for DSL at those same boundaries. There are
now very few urban exchanges not DSL equipped anyway.

----- Original Message -----
thenexus@ihug.co.nz wrote:

Question: How important is it for a DSLAM to be situated at
the local exchange? IE, could say a cheaper(?) repeater
unit be placed at the exchange, to then be fed back to a
DSLAM at the central office?

Could the residential copper be terminated into higher
quality cabling at the local exchange, to then (similar to
the above Q) be fed back to the central office?

What about in an urban situation, where the central office
is within the dsl spec distance?

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