Both radio and television, and soon coming to a laptop or desktop near you, if you're in the US. It's used for a variety of potential emergency situations, not strictly military, even though that was the original reason for its creation. I still get a knot in my stomach whenever I hear that squawking sound because of a near-miss between my house and a tornado several years ago. I was not at home, and could not call due to phone outage, and could not get there very quickly due to bad weather, downed trees and downed power lines. A minor case of post-traumatic stress disorder, I suppose.