A Brief History of the Emergency Communications Network

March 10, 2018 by Chantelle Dubois

What are emergency communications networks? How were they developed and who put them in place? Here's a look at how the US spreads information to its populace quickly in case of emergencies.

What are emergency communications networks? How were they developed and who put them in place? Here's a look at the history of how the US spreads information to its populace quickly in case of emergencies.

In 1951, President Truman established “Control of Electromagnetic Radiation” (CONELRAD), a system that would allow important messages to be broadcast over television and radio stations in the event of a national emergency. This was established under the shadow of the Cold War, a time when the world lived in constant threat of nuclear fallout.

Since then, the system has evolved, and today we have the Emergency Alert System and the Wireless Emergency System.

The usefulness of the system, which is managed by the FCC, is fully attributed to its reliability. Here’s a brief look at some of the history of the USA’s emergency communication infrastructure.

CONELRAD, the key station system

CONELRAD was the first widely established emergency communication network in the USA. In an emergency situation all television and radio stations would stop broadcasting their programs, shut down, and the emergency broadcast would begin transmitting on 640 AM and 1240 AM. In 1957, amateur radio stations would also be required to stop broadcasting during an emergency.


Advertising advised citizens to tune into 640 AM and 1240 AM during emergencies. Images courtesy of CONELRAD.


Telephone networks were used to connect to select stations referred to as “key stations” and other stations connected to those stations would be known as “relay key stations”.  Key stations would receive and broadcast from the Air Defence Control Center and, through the telephone system, would relay those messages to the relay key stations for transmission.

One of the challenges with creating a nation-wide broadcast system was that radio transmission could be used by enemies in “radio direct finding” navigation, and so a protocol was put in place that would require a station to transmit for 5 seconds, turn off for 5 seconds, transmit again for 5 seconds, transmit again for another five seconds, and then broadcast a 1 kHz tone for 15 seconds. Once this was complete, the station would stop transmitting, and another station would begin to transmit using the same protocol, before shutting down and another station taking over. This constant movement of transmission was meant to confuse any potential attackers from using the signal to home in on.

The challenges with CONELRAD was that it required people to be actively listening to the radio or watching TV when the broadcasts took over. During lightning storms, the system also was known to send out false alarms. Further, the system was unreliable, reaching only 20% of potential listeners, making it an unreliable system.

Eventually, a better system was devised and would replace CONELRAD in 1963.

Emergency Broadcast System

The EBS was an improvement on CONELRAD—the system expanded to include telecommunication common carriers, in addition to radio and television stations. The protocol was very similar, although the EBS used an Emergency Action Notification system to first send and verify emergency broadcasts to primary stations.

When a broadcast is meant to be sent, the radio station operators would confirm it using a code word which is changed daily, and then would be relayed to all participating stations. Any non-emergency broadcast transmissions were required to cease. Since ICBMs didn’t use radio direct finding, switching transmissions on and off was no longer necessary.

To get the attention of nearby listeners or observers, a dual tone was used in conjunction with an image advising that the EBS was active and that a message would be received soon from the White House. The tones, played simultaneously, were an 853 Hz and 960 Hz sine wave, creating an unsettling sound that would catch the attention of anyone near by. Eventually, the President would broadcast a message, or the station would broadcast national or local news.

In addition to being used during war-related threats, the EBS also expanded to use for local and state emergencies such as earthquakes or hurricanes.

Fortunately, during its tenure from 1963 to 1997, the EBS was never used to broadcast a national emergency alert. Although, it had been used over 20,000 times for regional emergencies relating to weather. The EBS also succeeded greatly in its testing. Stations were required to test the system on a weekly basis at random times, and not only would have to document their own tests, but document if they could receive signals from stations testing in the vicinity. This raised the EBS’ reach to 80% of the USA’s population, compared to CONELRAD’s 20%.

Tests were always carried out with clear indication that the EBS was being tested, although occasional false alarms did occur.

Emergency Alert System and Wireless Alert System

Today, there are even more channels to broadcast. The EAS broadcasts using: radio (AM/FM/UHF/VHF), television (digital, cable, and broadcasted),and satellite, expanding its reach and reliability greatly. The WEA broadcasts from cellular towers to all nearby WEA enabled cellphones. The EAS was established in 1997 and the WEA followed in 2013. 

Messages broadcasted to the EAS and WEA first go through a Primary Entry Point (PEP) station. There are 77 PEP stations in the USA, all with various redundancy equipment for transmission and power to ensure the stations continue operating through disasters. PEP stations work with FEMA. Messages broadcasted through the EAS utilize the SAME header, which allow decoders at broadcasting stations to decode the message sent in the format, starting with the header, an attention signal that is between 8 and 25 seconds long (either a single tone of 1050 Hz is used, or the EBS dual tone), the message which can be sent as a video, audio, or text, and then the end of message. EAS messages do not have error correcting, and so the messages are broadcasted three times so that parity correction can be done. 

WEA, being fairly new, is not necessarily a feature available in all phones. But, for the ones that are WEA-enabled, it is non-trivial to deactivate the feature, and there is no option to prevent Presidential messages sent through WEA to be blocked. When a WEA is received, the recipients phone rings as though a call is being received, and a short message is displayed on the screen indicating what the emergency is.

In the past, WEA has been used to alert people about abducted children, wanted criminals, and safety issues. When a WEA message is broadcasted, it is given priority over all other cellular traffic and every phone in the vicinity of a transmitting cellular tower will receive it. 


In New York City, a Wireless Emergency Alert was sent to help capture a criminal. Image courtesy of the Star


The EAS and WEA systems have much more rigid requirements than EBS did—testing, reliability, and redundancy are enforced at all stations. Today’s emergency communication infrastructure is capable of reaching approximately 90% of the US population within 10 minutes.

Despite this, the EAS is still subject to trivial security problems, such as failure to change default passwords on equipment. Between 2013 and 2017, EAS stations have been hacked three times with fake zombie apocalypse messages being broadcasted, as a result of default login credentials.


A fake zombie alert was sent out on the EAS three times in the past. Image courtesy of Threat Post.


Most recently, it is speculated that an operator error resulted in Hawaii receiving false reports of an incoming ballistic missile. While the technology and protocols behind the system have improved greatly, the human element is still subject to occasional mistakes. 



Emergency communication networks have evolved with the technologies used to relay them. As communication technologies become faster and more reliable, so do the methods through which we spread information in emergencies, saving lives more efficiently year over year.