Another 45 minutes on the phone, with "repair service" person who insisted that what I need is the exact opposite of what I asked about, and insists it will cost me a minimum of $249 for them to send someone out to confirm that she's completely wrong.

While the article doesn't help much with solving my most recent problems, I though it might be of interest for folks to see an opinion from the one other (thus far identified) phone-associated person who is not a TOTAL IDIOT.

At How do i...Connect a Second Phone Line?, which you may consult, although it's not really necessary:

"The first step is to perform a bit of what we call "Telephonic Archeology" by examining your present wiring to try to determine what goes where.

"Go around the house with a small straight screwdriver and "pull" all the phone jacks. For surface mount boxes, remove the single screw and gently pull the cover away. For jacks that are built-in to the wall, remove the two visible screws and gently pull the wallplate away from the wall until you can see how the wires are connected behind the plate.

"If you are being watched, stare intently at all these wires, rub your chin, and nod knowingly (this is very important). You may do this for an extended period if you wish. Congratulations...you've just done exactly what the telephone installer gets paid $200 for. "

Yep, Yessiree, You Betcha.

John