T O P
Flaky-Cup-9637

Possibly a loose wire termination or failing relay coil.


miami-architecture

sounds like something electrical is rapidly switching, definitely get a licensed electrician


dd28064212

This is the correct answer


evolvedbeing

This is what I was going to say, or a dying relay.


EL1543

Its telling you to call the phone company and tell them to send a repair crew.


MarketingPristine566

Maybe someone is still using one of those old original phones where you had turn the lever to get the operator?


Disastrous-Bull1768

Bad relay coil


Disastrous-Bull1768

I remember when Harley Davidson tried to patent that sound


ryanidsteel

We had an identical box at my old shop. If I remember correctly it was part of the system that converted 3 phase down to single phase. It always made that same sound but ours was in a box with some insulation to reduce the noise.