I'll say that was the most interesting siren video I've ever seen (and heard)

I located the patent document on the Sterling M coded siren. http://www.google.com/patents?id=ith5AAAAEBAJ&dq=sterling+siren I'd recommend downloading the PDF so the images can be rotated. It pretty much explains how the braking mechanism works. The first Sterling in this post is quite interesti...

Hamilton County, Ohio: Alert (steady tone): 5 minutes for Tornado Warnings and for Severe Thunderstorm Warnings that occur during a Tornado Watch. (can also be used for hazardous materials emergencies) Attack (long wail): 5 minutes for enemy attack. Test: Both signals are tested the first Wednesday ...

I live across the street from a dual toned Sterling M10. There isn't any others nearby, possibly none in the rest of the county.

Also, I once drove by that home grown siren that's been talked about recently (at Struble and Hughes Roads).