Emergency Broadcast System
The Emergency Broadcast System (EBS) was an emergency warning system in the United States, used from 1963 to 1997, when it was replaced by the Emergency Alert System.

# Purpose
The EBS 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 instituted in 1951. The EBS was later further expanded through an inter-agency effort with the FCC and the National Weather Service (NWS) to permit the system to be used for state and local emergencies. The EBS was replaced by the Emergency Alert System, or EAS, which was initiated in 1994 and fully implemented nationwide in 1997.
Although the system was never used for a national emergency, it was activated more than 20,000 times between 1976 and 1996 to broadcast civil emergency messages and warnings of severe weather hazards. Some dramatic works depicting nuclear warfare (most notably the 1983 made-for-TV film The Day After) included fictionalized scenes of EBS activations.

# System construction
The EBS was designed in a hierarchical system, with a relative handful of "primary" stations.  About three dozen around the country had direct communications with the White House (Primary Entry Points), some were connected to state emergency authorities (State Primaries), while others were responsible for information within their own "operational area" (Common Program Control Stations).  These stations would originate emergency programming, while other stations would monitor the primary stations for EBS messages to rebroadcast. In a few areas, "primary relay" stations served as relay points between primary stations and other stations that were unable to receive a primary station's broadcast.  Many areas also had an "alternate primary" in case one of the critical stations in the link were destroyed or unable to broadcast.  Additionally, the White House had a direct connection to all of the national broadcast networks and wire services, and affiliated stations were encouraged to monitor them during an emergency, as well.

# Activation procedure
Actual activations originated with a primary station, which would transmit the Template:Audio. This Attention Signal most commonly associated with the EBS was a combination of the sine waves of 853 and 960 Hz. Decoders at relay stations would sound an alarm, alerting the station operator to the incoming message.  Then each relay station would broadcast the alert tone and rebroadcast the emergency message from the primary station. The sine wave combination for the EBS signal was seen on the EBS slide from WXYZ-TV in Detroit, Michigan from late 70s to 1992.
A nationwide activation of the EBS was called an Emergency Action Notification (EAN).  This was the only type of activation which broadcast stations were not allowed to ignore; the FCC made local civil emergencies and weather advisories optional (except for stations that had agreed to be the "primary" source of such messages).
To activate the EAN protocol, the AP and UPI wire services would notify stations with a special message.  It began with a full line of X's, and a bell inside the teletype machine would sound ten times.  To avoid abuse and mistakes, the message included a confirmation password which changed daily.  Stations that subscribed to one of the wire services were not required to activate the EBS if the activation message did not have proper confirmation.

## False alarm of 1971
Despite these safeguards, the system was inadvertently activated at 9:33 AM EST on February 20, 1971.  Teletype operator W. S. Eberhardt accidentally "played the wrong tape" during a test of the system.  As a result, an EBS activation message authenticated with the codeword "HATEFULNESS" was sent through the entire system, ordering stations to cease regular programming and broadcast the alert of a national emergency.  A cancellation message was sent at 9:59 AM EST; however, it used the same codeword again.  A cancellation message with the correct codeword, "IMPISH," was not sent until 10:13 AM EST.
This false alarm demonstrated major flaws in the EBS system.  Many stations had not received the alert, but more importantly, the vast majority of those that did ignored it.  The only station in the country that shut down as mandated by FCC rules was WSNS-TV (Ch 44) in Chicago.  Numerous investigations were launched, and several changes were made to the EBS.  Among them, the on-air alert announcement was streamlined, eliminating language that warned the audience of an imminent attack against the country.

# "If This Had Been an Actual Emergency..."
Although it was never used, the FCC's EBS plan involved detailed procedures for stations to follow during an EAN.  It included precise scripts that announcers were to read at the outset of the emergency and whenever detailed information was scarce.  Among other things, citizens were instructed not to use the telephone, but rather continue listening to broadcast stations for information.
As official information began to emerge from various sources, non-primary stations were to broadcast it according to the following priority list:
- Messages from the president
- Statewide emergency information
- Local emergency information (for a station's operational area)
- National programming and news (other than a presidential message)
A presidential message was always required to be aired live during an EAN.  For other information, stations were to follow the priority list to decide what should be disseminated first.  Lower priority official programming was to be recorded for the earliest available rebroadcast.
Participation in EAN emergency broadcasting was done with the "voluntary cooperation" of each station (as noted in the classic test announcement).  Stations that were not prepared to be part of the national EBS network were classified as "non-participating" by the FCC.  During an EAN, a non-participating station was required to advise listeners/viewers to tune elsewhere to find emergency bulletins.  The station's transmitter would then be turned off.  Non-participating stations had to remain off-the-air until the EAN was terminated.  Under no circumstances could any broadcast station continue with normal programming during a national emergency.

# Testing the system
Until the system was superseded, radio and television stations were required to perform a Weekly Transmission Test Of The Attention Signal and Test Script on random days and times between 8:30 A.M and local sunset. Stations were required to perform the test at least once a week and were only exempt from performing the test if they had activated the EBS for a state or local emergency or participated in a coordinated state or local EBS test during the past week.

## Original plan
Early in the history of the EBS, tests and activations were initiated in a similar way to CONELRAD tests. Primary stations would turn their transmitters off for five seconds, back on for five seconds, off for five seconds more, then would go back on air and transmit a 1000 Hz tone for 15 seconds to alert secondary stations. This quick off-and-on became known to broadcast engineers as the "EBS Stress Test", as older transmitters would sometimes fail after the quick cycling on and off.  This became unnecessary as broadcast technology advanced and the two-tone alarm was developed.

## Later test pattern
Later on, the EBS Stress Test was scrapped in favor of the following procedure:
1) Normal programming was suspended. Television stations would transmit a video slide such as the one illustrating this entry (numerous designs were available over the years). One of the following announcements written below was transmitted:
- "This is a test. For the next sixty (or thirty) seconds, this station will conduct a test of the Emergency Broadcast System. This is only a test."
- "(name of host station in a particular market) is conducting a test of the Emergency Broadcast System.  This is only a test."
- "This is a test.  This station is conducting a test of the Emergency Broadcast System. This is only a test."
- "The following is a test of the Emergency Broadcast System."
2) The Attention Signal was transmitted from the EBS encoder for 20 to 25 seconds. At the special request of the FCC, however, this step was occasionally (though rarely) skipped.
3) The announcement written below (depending on the variation) was transmitted. The first part read:
- "This is a test of the Emergency Broadcast System. The broadcasters of your area in voluntary cooperation with the FCC and other authorities (or, in later years, "federal, state and local authorities") have developed this system to keep you informed in the event of an emergency."
There were a number of variations for the second half of the statement.  During the early days of the system, stations other than the designated primary station for an operational area were required to shut down in the event of an emergency (reminiscent of the CONELRAD days), and the message was a variation of:
- "If this had been an actual emergency, you would have been instructed to tune to one of the broadcast stations in your area."
- "If this had been an actual emergency, you would have been instructed where to tune in your area for news and official information".
In later years, as it became easier for stations to record and relay messages from a primary station, and the risk of hostile bombers using broadcast signals to navigate lessened due to the development of ICBMs, the requirement to shut down in the event of activation was dropped, and the message became:
- "If this had been an actual emergency, the Attention Signal you just heard would have been followed by official information, news or instructions."
As the EBS was about to be replaced by its successor, the aforementioned Emergency Alert System, some stations used the following variant:
- "This station is testing its Emergency Broadcast System equipment. The EBS will soon be replaced by the Emergency Alert System; the EAS will provide timely emergency warnings."
The test concluded with one of the following phrases:
- "(sponsoring station in a particular market) serves the (name of operational area) area.  This concludes this test of the Emergency Broadcast System."
- "This station serves the (name of operational area) area. This concludes this test of the Emergency Broadcast System."
These variations were heard in different parts of the country throughout the years depending on FCC regulations at the time, local preferences, and whether the specific station performing the test was a primary EBS station or not. At least one version made explicit reference to an attack on the United States as being a possible scenario for EBS activation.  The announcement text was mandated by the FCC.
Stations had the option of either reading the test script live, or using recorded versions. Jingle producer Terry Moss (of "L.A. Air Force" fame) offered a sung version of the most common script on his Cheap Radio Thrills and WHEN radio in Syracuse, New York had their own sung version. In the late 1970s, however, the FCC prohibited singing the test script or reading it as if it were a joke.

## Purpose of the test and cultural impact
The purpose of the test was to allow the FCC and broadcasters to verify that EBS tone transmitters and decoders were functioning properly.  In addition to the weekly test, test activations of the entire system were conducted periodically for many years.  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.
The weekly broadcast of the EBS test message made it part of American cultural fabric of the era, and became the subject of all kinds of jokes and skits. Several people have testified about being frightened by the Test Pattern as children, and actual emergencies scared them even more.