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CONELRAD (Control of Electromagnetic Radiation) was a method of emergency broadcasting to the public of the United States in the event of enemy attack during the Cold War. It was intended to serve two purposes; to prevent Soviet bombers from homing in on American cities by using radio or TV stations as beacons, and to provide essential civil defense information. U.S. President Harry S. Truman established CONELRAD in 1951. After the development of intercontinental ballistic missiles reduced the likelihood of a bomber attack, CONELRAD was replaced by the Emergency Broadcast System on August 5, 1963, which was later replaced with the Emergency Alert System in 1997; all were administered by the Federal Communications Commission (FCC).[1]

Unlike its successors, the EBS and EAS, CONELRAD was never used for nor intended to be used for severe weather warnings or local civil emergencies.



Prior to 1951, there was no method that the U.S. government could use to broadcast warnings to citizens in the event of an emergency. However, radio stations and networks could interrupt normal programming and issue a bulletin in the event of an emergency, as happened during the attack on Pearl Harbor on December 7, 1941, as well as the first successful tornado warning near Tinker Air Force Base in Oklahoma City in 1948. This type of broadcasting was the forerunner to CONELRAD.

The CONELRAD concept was originally known as the Key Station System. According to an FCC document created during the "Informal Government - Industry Technical Conference" on March 26, 1951:

CONELRAD had a simple system for alerting the public and other "downstream" stations, consisting of a sequence of shutting the station off for five seconds, returning to the air for five seconds, again shutting down for five seconds, and then transmitting a tone for 15 seconds. Key stations would be alerted directly. All other broadcast stations would monitor a designated station in their area.

In the event of an emergency, all United States television and FM radio stations were required to stop broadcasting. Upon alert, most AM medium wave stations shut down. The stations that stayed on the air would transmit on either 640 or 1240 kHz. They would transmit for several minutes, and then go off the air and another station would take over on the same frequency in a "round robin" chain. This was to confuse enemy aircraft who might be navigating using Radio Direction Finding. By law, radio sets manufactured between 1953 and 1963 had these frequencies marked by the triangle-in-circle ("CD Mark") symbol of Civil Defense.[3]

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