[ale] Telco Terminology

[Mike Fletcher]

>>>>> "Alan" == Alan Bowman <aminus at mindspring.com> writes:

    Alan>  So that I (and possibly others) can better follow the
    Alan> recent thread regarding xDSL lines, could someone please
    Alan> define the following terms:

    Alan> CO 

Central Office.  Where the phone company keeps the switching
equipment.

    Alan> SLC 

I think Subscriber Line Concentrator.  Sort of a mini-switch, or a
phone line multiplexor.  The phone company can run 2-3 T1-s (a
physical circuit that can carry 24 different phone lines) to a SLC at
(say) an appartment complex and then break out individual lines to
each appartment.

    Alan> demarc 

The line of demarcation between where the phone company's lines enter
your house and becomes your lines (which you're responsible for).

    Alan> physical copper line

Just what it sounds like.  In olden times, the phone company used to
run a complete, uniterrupted circuit from the CO to each subscriber
(hence the term "local loop").  It's more efficient to run a couple of 
T1's or a single bundle of fibre to one SLC.

    Alan>   And could I also get a definition of, and an explination
    Alan> of the differences between:
    Alan> ADSL 

Asynchronous Digital Subscriber Line.  More bandwith in one direction
(usually larger downstream to the subscriber).

    Alan> SDSL 

Synchronous Digital Subscriber Line.  Same bandwidth both ways.

    Alan> IDSL

No clue.

	All of these are forms of squeezing a whole bunch of data
through plain old copper telephone wiring.  Because they were designed
for use over copper, you're pretty much out of luck DSL-wise unless
your phone lines are old enough to be copper (as opposed to fibre) but
not old enough that the lines are in too poor of a condition to carry
DSL signals.

-- 
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