The Emergency Broadcast System (EBS) was an emergency warning system in the USA.

It was initiated in 1963 at the height of the civil defense era, to allow the president to address the entire nation in an emergency. EBS replaced the CONELRAD system that was instituted in 1951. The EBS was later further expanded through an interagency effort with the FCC, and the National Weather Service (NWS), to permit the system to be used for state and local emergencies. EBS was replaced by the Emergency Alert System (EAS) in 1997.

The system was never used for a nuclear emergency, though it was activated more than 20,000 times between 1976 and 1996 to broadcast civil emergency messages and warnings of severe weather hazards.

Until the system was superceded, radio and television stations were required to perform the Weekly Transmission Test Of The Attention Signal and Test Script a minimum of once a week at random days and times between 8:30 A.M and local sunset, unless during the test week, they have activated the EBS for a state or local emergency or participated in a coordinated State or local EBS test.

Test procedure

1) Normal programming is suspended.

2) The announcement written below is transmitted. "This is a test. This station is conducting a test of the Emergency Broadcast System. This is only a test."

3) The special attention signal is sent. Broadcast the two-tone Attention signal from the EBS encoder for 20 to 25 seconds.

4) The announcement written below is transmitted. "This is a test of the Emergency Broadcast System. The broadcasters of your area in voluntary cooperation with the Federal, State and local authorities have developed this system to keep you informed in the event of an emergency. If this had been an actual emergency, the Attention Signal you just heard would have been followed by official information, news or instructions. This station serves the (name of operational area) area. This concludes this test of the Emergency Broadcast System."

The purpose of the test was to allow the proper functioning of EBS tone transmitters and decoders to be verified. In addition to the weekly test, test activations of the entire system were conducted periodically for some years before being discontinued. These tests showed that about 80% of broadcast outlets nationwide would carry emergency programming within a period of five minutes when the system was activated.

Variations of the above announcement were heard in different parts of the country. At least one version made explicit reference to an attack on the United States as being a possible scenario for EBS activation. The annoucement text was mandated by the FCC, including the "voluntary cooperation" clause, which was not true, as broadcast outlets were required by law to participate.

The weekly broadcast of the EBS test message made it part of the U.S. cultural fabric of the era.

Network construction

The EBS was designed in a hierarchical system, with a relative handful of "Primary" stations that had direct communications with the White House and regional authorities. These stations would originate emergency programming, and other stations would monitor the primary stations for EBS messages to rebroadcast. In a few areas, "primary relay" stations were designated that served as relay points between primary stations and other stations that were unable to receive a primary station's broadcast.

Activation procedure

Actual activations originated with a primary station, which would transmit the test tone. Decoders at relay stations would activate, alerting the station operator to the need for activation. Then each relay station would broadcast the alert tone and then commence rebroadcasting programming from the primary station.

To prevent inadvertent activations and abuse, a ten bell alarm would be transmitted by the AP and UPI wire services along with a confirmation password during nationwide activations. Stations who subscribed to one of the wire services were not required to activate EBS if the teletype was operating but did not have a confirmation.