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Here are some of the main words conserning siren terminology and such.

Omni directional siren- a type of siren which spreads its sound coverage simoltaneously around in a three-hundred-sixty degrees pattern on a horisontal axis at the same time. In other words, the siren can be heard in all directions across an area of land at the same time.

Directional siren- a type of siren which concentrates its sound output in a straighter beam, usually at an estimated twenty to seventy degrees average. The siren head can stay fixed in one direction or can spin, delivering the sound energy in a circle, one direction at a time.

Mechanical siren- a type of siren which uses a rotor and stator to produce noise. As the rotor spins, its openings, or ports, allign with the stator ports producing a burst of sound, the rotor being an impeller, and the stator being a drum which the impeller spins in with the same number of ports as the rotor. Also, a mechanical siren is spun by means of a hand or any other non-electric rotation source.

Electro-mechanical siren- a mechanycal siren, only spun by an electric motor.

Rotor- also known as a chopper, is an impeller found inside a mechanical siren. The impeller spins a very high speed, averaging around three-thousand RPM (Revolutions Per Minute). The rotor has a row of openings, or ports. It sometimes even has two rows of ports. As the rotor spins, its holes allign and close with the holes in the stator with each spin of the rotor. And as the rotor's openings align with the stator openings the air is pushed out. And as the holes of the two move, they also move away letting no air out.

Stator- is a drum, a drum which has the same ammount of openings as the chopper on its sides. As I've said above, as the chopper spins inside it, with each spin, the holes allign at one time, causing the air to be pushed out. And as the chopper spins along, the holes will close off again, and than allign again, close, allign, you get the picture.

Electronic siren- a siren type which simply uses amplifiers and speakers to produce the sound. The speakers are sometimes called drivers. Electronic sirens, as well as mechanical/electro-mechanical variants can be omni directional or directional.

Dual tone siren- a siren which has two ranges of tone frequencies comming out of it at the same time. For any mechanical sirens, this may be having a rotor/stator with two rows of ports, each one with a different port number, or two rotor/stator sets, each set with a different port number. For an electronic sirens it is simply a matter of electronic speaker manipulation.

Single tone siren- a siren which only has one tone frequency comming out of it.

Blower- used in some electro-mechanical siren models, the blower feeds extra air to the rotor/stator assembelly for an extra boost in sound power.

Sollenoid(s)- also used in some particular models, sollenoids are made to make the siren sound as of a high frequency sharply alternating into a low frequency, and back again, than down again, ect. Hence the signal name, hi-lo. To produce hi-lo the siren has to be a dual tone siren so as to make a high frequency and low frequency. What happens in some sirens is that as one chopper spins with a free supply of air [it is making noise], the air supply is blocked off to the second chopper so it cannot be heard. Than the chopper that was once heard now has its supply of air blocked so it cannot be heard and the chopper that was previously not heard is now heard, with a supply of air. Than it goes back and forth like that; as one is heard the other one isn't, then the other one is heard, the first one isn't, and so on back and forth, you get the picture. The way to block the air to each specific chopper is to do it with those sollenoids I told you about. Also, the sollenoid(s) can be infront of the rotor/stator holes so that the sound cannot escape from one rotor, meaning that it is the same procedure, only this way, instead of blocking the air to the rotor, this way blocks the sound from escaping the rotor, so the sound stays inside the rotor rather than being blasted out while the other rotor is not blocked. Than, ofcourse, it's going to alternate back and than forth again, and back an forth again until it is turned off.