William Sommerwerck wrote:

Don't forget that the lines themselves vary in quality, and therefore in
their data-carrying capacity. If the lines are mediocre, there's little
you or any phone company can do about it.

Before I went to Comcast, I asked about DSL. The phone lines in my area
use some sort of digital distribution that just isn't compatible with DSL.

Yup those neighborhood clusters of 3 tan boxes are "RT"s, or remote
terminals. They are basically a several hundred subscriber line central
office, but with relatively limited features. They actually CAN support
DSL if another box is added, but most phone companies opt to keep it
simple. These things run off a T-3 line or fiber version of that.

Jon