People with important secrets do not yet whisper them into radio telephones because they know that anyone with a radio set can eavesdrop. But last week in Manhattan, Sergius Paul Grace, vice president of Bell Telephone Laboratories, demonstrated how radio conversations may be absolutely private. Mr. Grace played a phonograph record into a special type of microphone. The audience heard an ordinary speech. Then he took away the microphone, played the record alone. Listeners heard a gibberish of strange grunts and squeaks.
Mr. Grace instructed one of his audience to say "Play-o-fine crink-a-nope"...