Ichor, you're correct. It is an air raid siren. Specifically a F-S Thunderbolt 1003. Even though my town doesn't need a warning siren system, I've come to like air raid sirens because of how loud they are. And a siren enthusiast's favorite siren is almost always a F-S Thunderbolt. Why? The Thunderbolt was THE scariest sounding siren that was ever made!! Unfortunately, all variants of the Thunderbolt (1000, 1000T, 1003) have been out of production since 1990. <!-- s:cry: --><img src="{SMILIES_PATH}/icon_cry.gif" alt=":cry:" title="Crying or Very sad" /><!-- s:cry: --> No siren made since has been able to match it in ability to get your attention.
By the way, when one of these Thunderbolts go off, you can hear it as far away as 4 miles (!).