lucwarm:
DAVW is on the right track. Disconnect and reconnect one at a time. Even if the working phone line is connected correctly, other lines might be causing the static on it.
Start at the service box. This is not a new home, so you may or may not have a box on the outside of the house.
If you do, it’s grey, about 10 inches square, and has two “doors” on it. The left one is marked for you to open. Unscrew the Phillips screw and you’ll see some wires and jacks.
The feed can consist of a number of wire sets, starting with four pairs.
white-blue/blue - line1
white-orange/orange- - line2
white-green/green line 3
white-brown/brown - line4
I’m assuming you only have one phone line now. There should be a plug in the jack for the white-blue/blue pair. This should go to some kind of junction box inside the house. In an installation without an outside service box, this will be where the service enters the house. You would see your white-blue/blue feed here.
In a new installation, wires from all phone jacks would also meet here.
Like this:
Junction
box
|Feed|======jack1
|…|======jack2
|…|======jack3
|____|
However, most older homes will have had phone jacks added from one to the other.
Like this:
Feed-------jack1------jack2------jack3
All green/red pairs from the jacks should connect here to the white-blue/blue pair from the feed. Green (tip) goes to white-blue. Red (ring) goes to blue. This is where you want to disconnect and reconnect one at a time. Connect one green/red set, go around the house with a working phone, and see what works and is non-static. If you get static on some and not others, open each wall jack on this string and see what’s connected there. Disconnect and reconnect, keeping only non-static connections. Do this until all lines at the junction box are done. Then go to the wall jacks still causing trouble and the one feeding it. Open them up and see what’s up. At each wall jack, only the green/red pair should be used. Just leave the black/yellow pair unconnected.
If you want a second line, you follow the same procedure with the white-orange/orange feed and use the black to white-orange (tip) and yellow to orange (ring) to each jack on which you want the second line.
If a jack is to be a single-jack-two-line setup (for a phone with 2 lines) hook the yellow/black feed to the yellow/black jack wires. If there are to be 2 jacks side by side, one for line 1 and one for line 2, hook the black feed to the green jack wire and the yellow feed to the red of the second jack.
As you fix one problem, test all jacks which you tested and were working before, as you may fix one thing and introduce a problem on another.