I will only delve into the technical aspects of this thread.

The so-called frog horn the TS was referring to might be the 'air horn' setting of the siren.

aga,
That could be the standard siren system they sell in Banawe. The amplifier is of the hide-away variety so maybe the only part you see is the control panel itself.

The mic and P.A. clear up traffic very vast.