Technical limitations to qualifying for DSL

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Unfortunately, ordering the service isn't the only obstacle between you and DSL. There are a few stumbling blocks, especially prevalent in the Tucson area, that prevent a number of people from qualifying.

First: DSL services can only run over straight copper phone lines with no digital conversions.

This means that an office location using a PBX phone system wouldn't qualify for DSL. A PBX system is digital, and thus prevents the DSL conversion from happening.

(The location might qualify if a straight analog phone line from US West was run to the location, but there are no promises that even that would qualify.)

Also, if fiber optic cable is used anywhere between your house and US West's central office, the line cannot be converted to DSL. Some newer housing areas have used fiber optic cable for the housing units. While this is great for voice, it means no DSL.

Second: You need to be within about 15,000 feet of a phone company's central office to get the service. In testing the circuits, US West has found that some people as far as 18,000 feet away from a central office can get DSL service.

The 15,000 foot limit is because of signal loss. Typically, if you are over 15,000 feet away from the central office serving your location, too much data will be lost to make the service usable.

You can get a rough idea of how far away you are from your phone switch by using a web tool StarNet has online. You give it your address and phone number (or first three digits of your phone number) and it will tell you the driving distance between you and your phone switch. Since the phone lines generally follow the roads, this should give you a fairly close appoximation.

You will find the distance measuring tool at http://www.azstarnet.com/~uurtamo/commensurate.html

Third: Even if you are within 15,000 feet, you still might not qualify because of line conditions and signal loss.

Certain devices and wiring may prevent a line that would otherwise qualify from doing so.

For example, US West commonly uses "pair gain" devices like SLCs. An SLC is like DSL in that it converts a line to use digital instead of analog. However, the increased capacity is then used to carry more phone lines instead of enhancing the one.

US West commonly uses these devices where they have run out of wires for new lines. (It costs a lot less to setup an SLC than it does to run more copper wires from the central office to the home/business.)

These devices can have a detrimental affect on modem connections and automatically disqualify you for DSL.

Also, there are some older devices used to boost voice quality that will disqualify a line.

Another big culprit is older phone wiring (either in the home or somewhere between the home and US West's central office). The older wiring causes more signal loss and could disqualify a line that is within the distance limit otherwise.

Note: When you order DSL you should be aware that US West equates signal loss to distance. Thus if you order DSL, you may be told that you are too far away from the central office when you are not. This result typically means that there is something on the line that is causing excessive signal loss.

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