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April 1943

1943JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecemberThe following events occurred in April 1943: April 1, 1943 (Thursday)SIGSALY, referred to as the X System vocoder or "Green Hornet", went into operation for use in secure phone conversations between U.S. President Franklin D. Roosevelt and U.K. Prime Minister Winston Churchill.

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