By 1943, Donald Barchok filed a patent for a radar system using the abbreviation IFF in his text with only parenthetic explanation, indicating that this acronym had become an accepted term. In 1945, Emile Labin and Edwin Turner filed patents for radar IFF systems where the outgoing radar signal and the transponder's reply signal could each be independently programmed with a binary codes by setting arrays of toggle switches; this allowed the IFF code to be varied from day to day or even hour to hour.