When the Dept. of Homeland Security recently got rid of the rainbow threat level system (that seemed to always be orange) it reminded me of this Cold War era card I had seen in my Grandfather&rsquo;s billfold.&nbsp; CONELRAD was part of Civil Defense, the Great Great Grandfather of the Dept. of Homeland Security.
The CONELRAD (CONtrol of ELectronic RADiation) system was set up in 1951 with a dual purpose in mind.&nbsp; The first was the shutting down of radio (and eventually TV) signals so that enemy bombers couldn&rsquo;t use their transmission as a homing beacon to large cities.&nbsp; This method of navigation had been used during WWII including by the Japanese when they attacked Pearl Harbor. &nbsp;&nbsp;So there was some good basis for this step.
The second purpose of this system was the taking control of the airwaves.&nbsp; What would happen is all stations would go off the air and then different stations would take turns broadcasting emergency information on AM 640 or 1240.&nbsp; This would mean that the origination of the signal would geographically come from different locations, thus making it useless as a beacon.&nbsp; &nbsp;The government could then broadcast to the public prior to and after a nuclear attack.&nbsp; This information could come from a local State run agency or all the way up to the President.&nbsp; The government viewed this system as such an important part of Civil Defense that a law was passed stating that all radios manufactured must carry the CD logo on the dial at 640 &amp;amp; 1240.&nbsp; The advent of ICBMs made the idea of mixing up the transmission locations useless so the law was rescinded in 1963 when CONELRAD was replaced by the Emergency Broadcast System.&nbsp; (If you ever see a radio with the CD triangle on it, you can know with certainty that it was built sometime between 1953 to 1963.) 
Chicago was always considered a major Soviet target, so keeping a card like this in your wallet was probably not unreasonable.&nbsp; Though the idea that you were supposed to have the wherewithal to be able to remember that you had this card after hearing those horrid air raid sirens (the same used to announce tornados), that is bit beyond me.&nbsp; I would have been too busy whimpering in a corner to bother reading both sides of these little instructions.&nbsp;&nbsp;