It’s not relevant to me, i’m in a different country, but in i’ve seen daily completely turn off your hidden phones, and only turn them on when it is safe because the alert will still blare when you turn on you phone the entire week before the test and also months before. Certain circles take warning each other about ‘Loud Day’ seriously.
I think it pointed out the right direction at least once, back when i was doing tech support (xp and pre-xp). Back when the toolkit includes whole stacks of cd’s containing every driver known to exist. I don’t even remember what it is, but it was something Realtek.