When we returned from the Lair, I couldn't get our DSL to work. With a couple evenings' diagnostic efforts I intuited that the problem was in my phone wiring.
These early 1950s homes didn't come with phone wires (or phones) installed. Consequently, the retrofit of phone lines to these older houses often took the form of four conductor wire strung around the house under the eaves and along the edge of the roof and then through an exterior wall into each room. As unaesthetic as this seems, most slab floored houses and many raised foundation houses used this retrofit method back in the day.
Over the years, the sheathing on the wires has deteriorated to the point that they are no longer weather-proof and corrosion can set in. I've repaired some failing wires before, but this time I couldn't find an obvious problem area - rather I found several areas where there was minor corrosion. For POTS (plain old telephone service) a little corrosion between conductors or on one conductor alone doesn't seem to be a big problem - our phone still worked OK (a bit of a noise problem, but not impossible). For DSL, it's a much bigger problem.
With a leap of faith in my intuition, I disconnected all the phone lines and replaced them with a hastily prepared Cat 5e wire run right to my DSL modem. Bingo! It worked. The failure mode was identified. But now I have to re-wire all the phone lines the right way (without outdoor wire runs) and with Cat 5e or Cat 6 wire.
Now I'm wondering if I shouldn't run some video along with the new phone lines.
HomeTech seems to have useful tutorials with pictures along with a good selection of appropriate parts.