What is this?

[Mister_Penetrator]

http://www.wisconsinsirens.com/SirensFAQ/misc.htm

[Blasty]

Most of what we know about them is on the name plate.

Without actually seeing inside it, many people believe that it's a dual toned model, housing a rotor/stator assembly in the base of the front projector, and one in the rear chamber that has the hook-shaped horn coming off it.

You can't see it there, but the front is actually a horn within a horn. The way I think it works (I'm not passing this off as a solid fact yet) is this:

Air enters through the central horn and sound is dispersed through the space between the inner and outer horns. On the back, air would come in through the little protrusion on the back and exit through the hook-shaped horn.

Here's a photo showing the front of this siren, with the coaxial horn arrangement: http://winnipeg.urbex.ca/Ogilive/46.jpg

You can also see one of these in the movie, "Blues Brothers," but it has been butchered by Hollywood to be a giant megaphone. An electronic horn has been placed inside it, and the rear horn has been blocked off.

[q2bman]

someone has to film that thing in action!!! looks like an Allertor

[Daniel]

These things used to be found all over Canada and that nearly all of them were removed fairly recently. I understand that they were originally single tone, but because of Civil Defence requirements, were modified with a smaller rear rotor to accomplish this. I believe that they were minor 3rd sirens like the 2T22 -- the favoured interval for all British Commonwealth countries since WWII and the Carters sirens. They were manufactured by Canadian Mystery, Ltd. in Moose Jaw, SK, in the 1960's (okay, I made that part up).

[cdvtripleseven]

What is this?

It says what it is right on the name plate in the photos.

You can also see one of these in the movie, "Blues Brothers," but it has been butchered by Hollywood to be a giant megaphone. An electronic horn has been placed inside it, and the rear horn has been blocked off.

That thing on the car in the Blues Bros was a fabricated mock-up made
to look like one of the Canadian sirens. There is the one shot in the movie
where they show them walking towards the siren with a toolbox. The shot
is from behind the siren up on pole looking down. I think the movie was
shot in Chicago so who knows where they got the idea to use a Canadian
siren.

[Whelen Rules]

Chicago had these sirens at one time, or so i've heard.

[Gil]

Chicago had these sirens at one time, or so i've heard.

I would say that is ver unlikely as Chicago has always used
Federal Signal products.