DescriptionCrystalradioadvertisement.png English: Photo of an American family in the 1920s listening to a crystalradio. From a 1922 advertisement for Freed-Eisemann
published In a supplement
year record, by more
to ‘ “Lloyd** e List and Ship!png <le- . previous
than 7 000,000 bushels, touting
xette."
t07.M6.034 bushels
tube a few radio receivers used a combination of an earphone and a carbon microphone to amplify the signal. This drawing is from an advertisement for microphones