That siren is doing wail cycles. The damper is most likely hooked directly up to the motor's power supply, so when the siren motor has power going to it, the damper is raised. The reason it does not sound like much of a wail is because when the air supply is cut off, there is greatly reduced resista...

What he is doing actually is using a small stream of compressed air and is letting the vacuum impeller windmill. The airstream spins the impeller and the blades act as choppers to create the siren noise pulses.

The actual law that I saw regarding battery backup for sirens was that if more than 15,000,000 people live within a 50-mile radius, then the sirens within the 10-mile EPZ must be able to function without utility AC power. It seems like somewhat of an odd number to come up with, and there may be more...

The old system may have run fine, but in the event of a calamity at the power plant, it is very possible that AC power would go out...meaning most of those sirens would not be able to be activated. There are some 2001s in the system right now with battery backup, so I wonder if those will be removed...

Yes, the original Big Bertha did run separate engines for the compressor and chopper assemblies, giving it true constant output (in terms of CFM at least) over a range of pitches. The Chrysler Air Raid Sirens and Chrysler Victory Sirens have one engine for both, so there was decreased output when no...

I was going back trying to remember what the source was of the name "550" or "550-AT" for the dual-headed, rotating, dual-tone Federal siren, such as in Calhan, CO. The reason I ask is that I have something mentioning various warning devices (without pictures) and one of the list...

You cannot simply put the siren on less power; you can destroy a motor that way, if it were even at all possible to do that with their setup. Do you know where they they were measuring the sound level relative to the siren? 102dB seems like it would either be a 100-foot measurement, or an in-buildin...

St. Louis County also has a lot of ground to cover and I'm not sure what the loudest omni electronic siren was when they started putting them in. I'm assuming that the 3016s were definitely the best coverage for their cost with battery backup at the time. Of course normal wear and tear is an issue f...

It looks like a mobile Hormann ECN siren setup.

That Thunderbolt in Frontenac is definitely broken, as when I stood out there waiting for it to go off, I heard nothing but cars whizzing by on Hwy 40. There is another Thunderbolt just south of that one on Geyer Rd, right at the turn from South to East. I have no idea if that one works though. Usua...