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Note: This section is out of date and no longer maintained.
It is retained for the value of any residual information contained in it.
technical hurdlesOtherwise known as the No DSL? page.
The Telcordia website has (had) a section about Sapphyre loop qualification problems what's the problem with ADSL deployment ..
The number one most likely culprit if you cannot currently get DSL, is a DLC, (sometimes known as an SLC). Click DLC to read what this is, the explanation of the DLC issue will appear below this section.
Other problems include old copper circuits, wire too thin, load coils, bridge taps, DLCs (SLCs), bad connectors, mains hum leakage. These can all potentially ruin the chance that a local loop can provide DSL service, or rule out some of the faster speeds available.
Our experience with the Can I get DSL function show that currently, in the US, something like 50% of people cannot current get DSL, either because they are too far from the CO, or their CO is not DSL enabled yet, or they are behind some telephone architecture that is not DSL compatible yet.
If you cannot initially get DSL, all is not completely lost. You may find out there is an alternative phone company CO (wire center) that you can receive phone service from, nearer your house or business premise. This is more likely in highly built-up areas with many competing communication companies.
In the case of a DLC getting in your way, your Telco could also have plans to retro-fit it with new cards that allow DSL, in fact, up-rating DLCs is the solution of choice for most telcos. For an interesting document on the pros and cons of ADSL vs Fibre vs DLCs, check out Extending ADSL services to remote DLC locations tutorial.
If simple distance is the problem, you might be able to get IDSL, or RADSL, which stretch a little further than standard ADSL.
Bridge taps could be removed in your area, or with rollout experience, some DSL CLECs may extend the maximum foot limit they currently will entertain.
DLCDLC is A Digital Loop Carrier. An SLC is an AT&T variety, 'lightspan' is another.. you may come across either or any of these terms when hearing why you cannot get DSL.
Beginning in the 80s, to save money (copper loops are relatively expensive), Telcos began to install DLC frames around their existing wire centers, particularly in fast growing districts to provide for the flood of new lines required.
These local concentrators, although digital, and fibre optic, were designed before DSL was really available, and do not support it. They do support ISDN, however. It is estimated that nationally around 20% of US telephone lines are served from a DLC (the percentages vary slightly depending on which Telco you are talking about). Furthermore, about half of those DLCs are of an old type that do not support DSL. The newer half are installed capable of supporting DSL, but are only just being enabled for that..
All is not lost if you are on on either type of concentrator, the older ones can be retro-fitted with newer cards that will bring them to a level of DSL compatibility, but as of the end of 1999, the process has hardly started!
In summary, there is one chance in 5 that you are on a DLC, and at present cannot get DSL.
For or an interesting document on the pros and cons of ADSL vs Fibre vs DLCs, check out Extending ADSL services to remote DLC locations tutorial.
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