It’s weird but I get it. We already did fences so why not a collar I guess. Might be more anxiety inducing though. I prefer walls myself over a collar
This is just a wireless electric fence. Cue joke about the old lady and radio telegraphy[1]. :-)
The cow will hear a beep long before it gets zapped. It's the same as for invisible fences with pet collars.
(It doesn't, because cows will reach through and around a fence to get bites of tall grass on the other side, and if it doesn't shock them at that point they'll start pushing through to reach more.)