The Siren Board

There is a tri-tone Codewell in Jerome AZ. Some needs to go get a recording of it. Yes it is 3 different tones NOT just 3 same tone rotors.

Daniel wrote: A twin-rotor siren like the 2T22 will actually be louder than its single-tone version, the STH-10...

A good idea, but the 2T22 uses rotors about the size of a model 3's, spinning at 3450RPM. Those will kick out an equal amount of sound as the STH-10's much larger 22" rotor, not shared by any other federal omnidirectional siren.

I didn't realize that the STH-10 had that much larger of a rotor. I guess that explains why a 2T22 kicks up so much faster than the STH/L-10.

Justin Savidge wrote:I have not heard of a tri-tone siren as of yet.

Dual tone Thunderbolts are rated at 125dB @ 30m, single tone Thunderbolts are rated at 127db @ 30m, so splitting the chopper does have an effect on the output rating.

Isn't the 3T22 made of 3 tones, hence the 3T part?

sirenmaster2000 wrote:Isn't the 3T22 made of 3 tones, hence the 3T part?

No, the '3T' stands for the three tones it can produce; Alert, Attack, and Fire. The 22 is for the compliment of horns on the two stators. Ten on the bottom head for the lower note, and twelve on the upper head for the higher note.

3t22 continued:

Using electric solenoid actuated "valves" (each like a flue damper in a stovepipe) they open one damper to allow air to enter one rotor/stator assembly "siren".

Then that damper is closed which makes that siren mostly silent.

Simultaneously the other damper is opened to allow air to flow into the other siren allowing it to speak.

Alternately admitting air to the 12-port siren and then to the 10-port siren creates a Hi-Lo signal most often used as a signal to volunteer fire fighters to respond.

The 3t22 minor third interval Hi-Lo makes the most fascinating siren sound I havever heard - especially as it alternates as the siren rpms
increase up to full speed.

If I had more money, time, and a fully-stocked foundry and metal shop, I would build a 2T22-type siren with electric clutches between the motor and each siren head. The clutches would initially remain engaged until the motor got to full speed, then they would release alternately, allowing Rotor 1 to slow down while keeping Rotor 2 at full speed, then engaging Rotor 1 and releasing Rotor 2, then repeating this cycle. Each rotor would stay at full speed for a couple of seconds. Instead of a hi-lo tone like the 3T22 or the 1003, you'd get an alternate rising -falling sound which would definitely attract attention.

That is very similar to the two electronic sirens in an ambulance which operates in Aurora, CO.
Buthey are both athe same pitch level (range).

To avoid complication and clutches wearing out, I would simply have two sirens alternately being switched on and off.

Also when the clutch engages the second rotor, the first siren
would slow from the sudden added load, causing it's tone to drop and recover.

robert gift wrote:
Also when the clutch engages the second rotor, the first siren
would slow from the sudden added load, causing it's tone to drop and recover.

As described, the first clutch would release at the same time as the second engaged. This was inspired by the many towns I have visited where there are two similar or identical sirens side by side, presumably one for fire and one for civil defense. Why not put them in the same housing?

What costly redundancy.
Are you refering to.wns in Europe or the US?

(I find strange things done in Europe for no reason obvious to me.)
Like the Belgian toilets withe "plateau" in the middle of the bowl.

Why did they do that? (Sirens and toilets)

The Thunderbolt and 3t22 seem to accomplish fire, tornado and
CD signals very well withe least cost and complication.
I like the 3t22 better with it's minor third Hi-Lo.