How do air-defense warning systems send alerts to civilian populations?

Air-defense systems disseminate alerts to civilian populations primarily through the use of sirens and radio broadcasts. These methods are supported by extensive communication networks designed to ensure that warnings reach the public effectively.1

Historically, outdoor warning sirens gained widespread use during World War II to alert citizens of incoming air raids. During the Cold War, many of these sirens were installed in the United States specifically to provide warning in the event of a nuclear attack. While these sound-based systems are designed to be heard within a one-to-two-mile radius, they are often used in conjunction with modern emergency alert systems that utilize television, radio, and mobile device notifications to provide broader coverage and more detailed information to the public.2