I should have run phone lines through the big conduit, or maybe not since there may have been interference along those big aluminum wires. Since I haven't closed up all the stud bays yet, I decided to bring phone lines in through the back wall.
Here is a shallow trench near the same trench that holds the power lines. The half-inch PVC conduit holds two cat-5 (8-conductor) cables. I will use one cable for two phone lines, and one for computer interface.
The cable is buried under the driveway on the way to the house:
One cable goes into the house at the top, one cable goes to the phone box:
At the other end, the conduit goes around to the back of the garage...
... through the wall...
... and into electrical boxes:
Phone lines in front, the coiled wire in the back will eventually hook up to the computer.
So I have a phone and computer in the garage. They are old, but they work: