Got it, but something charges those batteries. There's voltage going into them; hence, there's a regulated circuit which undoubtedly has protection somewhere. I'll dig out the owner's handbook.

I guess I should add that when I bought the car the fuse box cover was off. Since everything seemed to work I concluded that perhaps the siren was an issue and someone pulled a fuse. Perhaps this isn't the case but I need to be sure before I make the rush to judgement and buy one of the last sirens on the planet.