English: A woman, Florence Violet McKenzie, sitting at a desk listening to an early radio in 1922. Radio broadcasting, which began around the time this picture was taken, caused radio listening to explode from a high-tech hobby to a hugely popular pastime during the Roaring 20s. This is a low power set using a single triode vacuum tube to amplify the signal, indicated by the hole in the front panel, used to check whether the filament was still glowing. Small sets like this did not have enough power to drive a loudspeaker and so had to be listened to with earphones. The tuning dial was not calibrated in kHz or MHz like modern radios, so radio stations had to be found by trial and error. When a radio station was found, the number on the dial was noted down as this woman is doing, so it can be found again. The top wire goes to a long wire antenna.