He likely means emergency sirens - I also had some friends I'd hang out with as a teenager who figured this out as well. As far as I'm aware this is still the

He likely means emergency sirens - I also had some friends I'd hang out with as a teenager who figured this out as well. As far as I'm aware this is still the case - but some sites are now encrypted radio. From what I've heard though, that encryption may not be the best implemented in all areas. It was pretty recently someone set off the civil warning sirens in I believe a city in Texas via this method as well. I'd like to say this was a one off experience in my "exploring civil infrastructure" days - but it's really just barely scraping the surface. The state of these systems makes you realize how much civilization is held together with tin cans and duct tape, and how much marketing fluff there truly is out there inspiring false confidence.