Raritan sonic polarity indicators

[Markhunter1097]

Opened up my AC panel to have a peek as you do when trying to avoid opening a beer. Not that I was going to do anything but I did find some interesting bits of equipment.
Anyone know what the raritan sonic polarity indicator does?
What are those black donuts
I also noticed a nice exposed wire that all the insulation had fallen off! That is a job for someone qualified

[GordMay]

The purpose of the Reverse Polarity Indicator is to allow the boat owner to verify that the electrical outlet on the dock is wired correctly. If the neutral wire of the incoming 120 volt AC shore power line should become "hot", the alarm will sound.
See ➥ https://nanopdf.com/download/reverse-polarity-alarm_pdf

The “doughnuts” look like current transformers, which measure AC ampacity.

[Markhunter1097]

Thx GM, I figured that was what they were for but wondered why they were called Sonic and not reverse?
Only thing I have googled that came up with nothing!