The way you describe it makes it sound like the rectifier failed and the siren auto transferred to the batteries, which would run it at a lower RPM. Not sure though, as I don't know how ASC sirens handle that.
Update. The model of the Carl Th. Malling sirens previously referred to as “Type A” and “Type B” have now been verified. They’re called 243L and 243S. L - Lille, translates to “small” in Danish S - Stor, translates to “big” in Danish 243L are the ones most commonly found in Greenland and have a sig...
Here Is A New Map For Washington State I Made: https://www.google.com/maps/d/edit?mid=1VcQ_NU2JdLX1nyKP3RSKqpXZ6uElSBA&ll=46.9570044997071%2C-121.53826606306899&z=6 There are already several Washington maps out there, including mine which is the most active and updated: https://www.google.c...
I believe that the sirens SirensofAustralia were referring to are pre-864 Whelens of some kind. At 3:54 in the video he linked you can hear them activate in air horn briefly, and it sounds just like pre-864 air horn.
As for the Whelen map, you are missing the Columbia Generating Station system and a few other locations in Washington: https://www.google.com/maps/d/u/0/edit? ... 704136&z=8
And the WPS-2802 in Waldport, OR is inactive.