Modern Mechanix, April 4, 1934 via Modern Mechanix blog: "The device, known as the 'radio advertising eliminator,' will operate the radio only when musical programs are coming over the air. Just as soon as any voice announcement is made from the station, the radio receiver is turned off and is not turned on again until the musical program resumes. It is believed that the new device uses a vibrating reed tuned to a predominant voice frequency to operate a relay which turns the set on and off."
