Coals of fire
I'd always heard stories about the strict requirements for radio announcers before the 1960's. Auditions included a long list of foreign words, and woe betide the candidate who missed one. (I encountered that list in 1965 when I tried to apply for an intern position at a local station; I handled the words easily, but my adolescent voice was too high.)
When did this practice start? Turns out it started at the EXACT start of professional radio, KDKA in 1920. This article from Radio World is worth reading:
Though commercial radio no longer has standards, NPR announcers still have to endure those "coals of fire" for pronunciation and grammar.