A number of emergency warning systems exist which allow broadcast networks to alert people of impending disasters and enable them to prepare for emergencies. The emergency warning systems use special warning or alert signals embedded in digital radio transmissions to automatically switch on the receiver equipment (if so equipped) and issue an emergency bulletin, alerting people to an impending disaster such as a tsunami or an earthquake. See Annexes 5A and 5B for examples of these systems.
The U.S. Emergency Alert System (EAS) is a public alert and warning system that uses the communications assets of EAS participants, including terrestrial broadcasters, cable television systems, wireless cable systems, Satellite Digital Audio Radio Service (SDARS) providers, direct broadcast satellite (DBS) services and wireline video service providers to allow the President of the United States the capability to address the American public during a national emergency. This system is designed to be available under all conditions. The system is also used by State and local authorities to deliver important emergency information, such as AMBER alerts. The National Weather Service (NWS) regularly uses the system to disseminate emergency weather alerts and advisories. A brief history and description of the U.S. EAS is given in Annex 5C.
The U.S. Advanced Television Systems Committee (ATSC) Mobile Emergency Alert System (M‑EAS) will build upon established ATSC Mobile Digital Television and Non-Real-Time standards to provide a robust and reliable alerting service for the public. It leverages the demonstrated excellent reliability of the broadcast digital television service to serve emergency needs that cannot be satisfied by other communications means that become damaged or overloaded during natural disasters. It provides a means for dissemination of both national and local alerts, and significantly extends alerting capabilities to include rich media such as maps and videos. A more detailed description of the M-EAS system is given in Annex 5D.
In many disasters people have lost their belongings and do not have a radio, or they are not radio listeners so do not own a radio. Ideally, radios and portable/mobile television receivers must be commonly available, so that the information being broadcast can be received and passed on across the disaster area.
The minimum requirement for an emergency radio should be that it does not require AC power and has both AM and FM bands. It should also have access to the shortwave band in regions where shortwave listening is prevalent, which will be used if the disaster is over a wide area. A wind-up radio would be a suitable choice for use in rural areas, where people would find it difficult to purchase replacement batteries. Some wind-up radios also include a torch or flashlight.
Details of systems for use in emergency communications are given in the following Annexes:
Annex 5A: Digital Radio Mondiale (DRM) Emergency Warning Functionality (EWF).
Annex 5B: HD Radio Emergency Alert System.
Annex 5C: U.S. Emergency Alert System (EAS).
Annex 5D: U.S. Mobile EAS for ATSC Mobile DTV.
Annex 5E: BBC Media Action - Use of new broadcasting technologies.