There are 77 radio stations designated as National Primary Stations in the Primary Entry Point (PEP) System to distribute presidential messages to other broadcast stations and cable systems. It contains information about who originated the alert (the president, state or local authorities, the National Weather Service (NOAA/NWS), or the broadcaster), a short, general description of the event (tornado, flood, severe thunderstorm), the areas affected (up to 32 counties or states), the expected duration of the event (in minutes), the date and time it was issued (in UTC), and an identification of the originating station (see SAME for a complete breakdown of the header).
All broadcast and satellite television and radio stations, as well as cable television systems, are required to participate in the system. The EAS regulations and standards are governed by the Public Safety and Homeland Security Bureau of the FCC. It is jointly coordinated by the Federal Emergency Management Agency (FEMA), the Federal Communications Commission (FCC) and the National Oceanic and Atmospheric Administration (NOAA). In practice, it is more commonly used at a regional scale to distribute information regarding imminent threats to public safety, such as severe weather situations (including flash floods and tornadoes), AMBER Alerts, and other civil emergencies. Despite this, neither the system nor its predecessors have been used in this manner, due to the ubiquity of news coverage in these situations. Like the EBS, the system is primarily designed to allow the President of the United States to address the country via all radio and television stations in the event of a national emergency. The EAS became operational on January 1, 1997, after being approved by the Federal Communications Commission (FCC) in November 1994, replacing the Emergency Broadcast System (EBS). These signals are decoded and encoded by special equipment at broadcast stations to automatically relay an alert to receivers and other stations only in the alert area.
The last signal indicates the end of message. The first signal encodes metadata about the alert including the type of alert and the location(s) it applies to. The signal is repeated three times for redundancy. The EAS uses a digitally encoded audio signal known as Specific Area Message Encoding (SAME), which is responsible for the distinctive "screeching" or "chirping" sounds at the start and end of each message. The Emergency Alert System ( EAS) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and both AM/ FM and satellite radio.