In my area we still have the tall wood telephone poles. The highest wires are part of the electricity distribution grid. The lowest wires are larger diameter cable bundles, which I suppose are telephone cables (or possibly some other communication lines). I have noticed that between almost every pair of adjacent poles and attached to the phone cable bundle are two teardrop-shaped frames which look to be about 18" long. The pointed ends of the teardrops point toward each other, and a smaller cable is wrapped around the rounded end of them. Also, once in a while there will be a black cylindrical object about 2’ long and about 4" in diameter with a corrugated surface attached to the cable.
What are these devices and what is their function?
(I tried to google it myself but got nowhere since I don’t even know what they are called.)
The teardrop things are used when bundling up extra cable so it doesn’t kink. The extra cable is usually for signal timing - it’s not always desirable for data to get from point A to Point B as fast as possible, so they work out the delay needed vs the propagation speed of the cable (some fraction of the speed of light) to determine how many yards of cable to add in a run. I’ve seen spots where it looked like they had to wrap up an extra half mile or more with a couple dozen loops between poles. Laying loose on the ground, it’s a mess, but once it’s lashed to the strand, it just looks like a wide spot in the wire.
You’ve got the size a bit too small, but whatever it’s official name, it’s covering a splice. Telephone lines are a plastic cover over at least a hundred twisted pairs of wires. Every house and apartment (not apartment building, but apartment) has 2 twisted pairs going to it. They all lead to a substation somewhere.