I CD Marks
(Civil Defence Marks)
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Sono due freccette visibili sulla scala parlante delle radio anni '50 e '60 dedicate al mercato americano (USA) Posizionate a 640 e a 1240 kilo cicli indicavano le due frequenze di emergenza su cui sintonizzare la radio in caso di guerra nucleare , nelle foto sopra riportate si vede un esempio per una radio della Sylvania , una Sanyo ed una Standard. Si riporta di seguito un breve documento in inglese per una breve storia di questi segnali obbligatori negli USA tra il 1953 ed il 1963. |
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During the height of the Cold War era, between 1953 and 1963, AM radios made in U.S.A. were required to have two little triangles (or triangles within a circle) on the dial, indicating the U.S. Civil Defence (or CONELRAD - CONtrol of ELectronic RADiation) frequencies, at 640 kHz and 1240 kHz. In the event of a national (U.S.A.) emergency, all other broadcasting would be suspended, and only these frequencies would remain on air, at low power. The transmissions would originate from locations that changed, so as to prevent any attacking enemy from homing in on the signal. Although it was instituted in 1951, it was not required on new radios until 1953. In 1963, the CONELRAD system was replaced by the Emergency Broadcast System (EBS), and radios were not required to have the CD marks. |