Sirens don't even need to be that complicated. A motor, a noise generator wheel (basically just a big spinning squirrelcage fan), and a horn. You could toggle them on/off with a simple relay/contactor.
More history, through January 2022, via JWZ's blog:
https://www.jwz.org/blog/2022/01/the-reason-the-tuesday-noon...
Still, a big loudspeaker is even simpler than a classical motorized siren. No moving parts!