Link is broken

The motor runs at 50 Hz with 2800 rpm, at 60 Hz it's 3450 rpm. That's why the american sirens are higher pitched with having the same amount of ports!

I could do a translation of it in a few days

What's in the document?

Something from the Netherlands https://youtu.be/IXO0H-qLXj0 I don't know much about the sirens there. They have Modulator system, which is tested at first Monday in month at 12.00. The modulators will disappear in 2017 because they cost too much. That's it. Do you know whether they have a Modulator...

https://www.youtube.com/watch?v=K-0gB9sE2Nk
It should be that video

I know Denmark had a siren system at some point before the 21st century. I found a photo of it somewhere but alas I know not where at this moment. Denmark has Whelens today from what I can tell. Here is a picture from the Zeppelin Museum in Denmark that has some siren in front of this Sherman tank....

Something from the Netherlands
https://youtu.be/IXO0H-qLXj0
I don't know much about the sirens there. They have Modulator system, which is tested at first Monday in month at 12.00.
The modulators will disappear in 2017 because they cost too much. That's it.

Wow! That's awesome! Really weird combination, but sounds pretty cool!

Looks still good!