IN the US, we started off with the CONELRAD system in 1951, then the Emergency Broadcast System in 1963, then the Emergency Alert System in 1997. Most people today know of the Wireless Emergency Alert System created in 2007 which supplements the EAS (nearly everyone has a cellphone today vs. being near a radio or TV).
The wireless system has been extended to include alerts for strong weather (tornadoes, hurricanes, wildfires, etc.) but also to include missing child alerts.
Growing up in the Cold War era, I'm used to these being used as an alert system (warning: loud)