So a few days ago, I went on a road trip down to Coos Bay, OR to record the biannual test of their system of 2 squareback Sentry Defenders that are in place for the Pony Creek Reservoir. This was the first time I had heard a Sentry Siren in person and the first time I have heard a full 3 minute cycle. It was quite the experience!
https://youtu.be/Mri4PcSjk6E