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Digital Subscriber Line (DSL)
(Page 1 of 3)
DSL (Digital Subscriber Line)
is the telephone companys answer for high-speed Internet
access. Available at a wide variety of data rates (whose availability
depend on your distance from the C/O, line quality, and how much youre
willing to pay to watch video and larger files from the Internet), DSL
is a nice, reasonably affordable option for those who qualify for it.
And that dear reader is the DSL
gotcha. Not everyone with a phone line can
get DSL. Sometimes it seems like your residences (or small business)
eligibility for DSL depends, as much on the phase of the moon multiplied
by the number of t-shirts you own, as anything. Reality is that a great
many factors go into determining whether a particular location
can subscribe to DSL.
Some of these include:
- Distance from phone company central
office (or CO) switch/wiring plant
- Quality of wire between your site and
- Make, model and age of the switch in the
- Simply, desire of the phone company to
install the necessary equipment to support DSL at the CO
Its the wire distance
One interesting twist of fate here is that distance equates to the length of the actual wires between you and the CO, not an as an owl flies or even as the car drives. For example, one of the authors living in an apartment complex has experienced a situation where her apartment cannot get DSL, although a friends apartment which is further as the car drives from the CO, can get DSL. Investigation with the phone company revealed that his physical wiring travels a slightly different path that enables him to come in just under the DSL distance limitations.
The maximum as the wire runs distance between you and the CO to be eligible for most types of DSL is 18,000 feet, a bit over 3 miles. DSL performance degrades over distance, and a user 5,000 feet away from the CO tends to get much better performance than a user 15,000 feet away. In fact, some DSL providers wont even sell service to subscribers more than 15,000 feet away from the CO because of the additional service issues theyre likely to encounter in maintaining the connection.
Do you feel lucky?
If youre in a fringe area, we can offer you one hint thats been known to work even if youve called up your local phone company to request DSL and been told that you dont qualify. Call a third-party DSL provider such as Earthlink. Theyve been able to magically pull off a DSL connection for someone only days after that person was told no, by the phone company!
There are different types of DSL
that provide different levels of throughput, and use slightly different
underlying technologies. Why multiple types of DSL? Two primary
reasons. First, the technology keeps advancing, and new versions
of the technology tend to be incompatible with older ones,
but are kept around because theyre still sufficient for many purposes.
Second, the slower/more expensive
ones often work in areas that dont qualify for the
faster, less expensive varieties. Now lets go over the features
of the most significant varieties of DSL (as of 2002):
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