Jim Thompson wrote:

My CO is directly across a park from my house, maybe a 1/4 mile max.

I have two phone lines with the same prefix.

If both phone are ringing, is the ringing synchronous... same cadence?

Do you have two friends? Why not have them call each number simultaneously
and find out?

This is called an "experiment."

For my call-blocker system...

I'm tempted to solve my lack of pairs (only three in the house) by
using a single pair as ringer, and electronically (photo-coupler
isolated) merge both ringing signals into my own low-voltage ring
generator.

Why not use the telco's "caller id" feature?

I've always screened calls by using a thing they used to call an "answering
machine." I don't know if such a thing is still made; I haven't needed one
in decades.

Good Luck!
Rich