National Emegency Warning system?
 

My 97 MB s600 has a noise that sounds like that old radio test of the emergency warning system. It is coming out of the speakers. I can stop it by pulling fuse 15 from under the hood, but that fuse also controls the wipers, signals and many other necessary key-related items. MB's 800 line thinks it could be a bad radio, but you need a special tool to pull the radio (I have it coming, but the car is effectively disabled in the meantime -- I live 200+ miles from the nearest MB dealer.) Others have suggested anti-theft, but the sound is defnintely coming from inside the car, which is inconsistent with any theft warning that I'm aware of. Anyone have any ideas?