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Note: This section is out of date and no longer maintained.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. distanceThe magic number for most DSL technology out there now is around 18000 feet. This is a function of the capability of copper to transmit high frequency over long distances. Past 18,000 feet, signal loss becomes increasingly unmanageable, bit errors rise fast, and therefore error-correction repetition of data means maximum reliable bandwidth is squeezed down to nothing. Thats the bad news.
The good news is that for the US, 18000 feet covers almost 80% of telephone subscribers (well, really, 80% of the US population). In addition, the phone company, in anticipation of the need for fast data rates and better quality lines, has been working on shrinking the average local loop lengths down in recent years, by installing smaller local hubs, known as DLCs or SLCs, that multiplex many lines onto optic fibre or other high quality lines that proceed on to the main switching centers. Most DLCs are not currently DSL capable, but the necessary hardware is out there, to upgrade them.
Many providers will not deal with you unless you are within 12000 feet.. this is to save the expensive of setting up a line to find that the quality precludes service, so being less than 18000 feet from your CO does not mean you can get DSL.
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When considering distance, the figures quoted by DSL equipment manufacturers assume good quality, thick, copper and under good conditions. For our area, even though our local loop is around 5000 feet, SDSL was limited to a maximum speed of 716k, half its theoretical maximum, probably due to oxidation and interference. (also see.. technical hurdles).
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.
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