1 янв 1940 г. - 1920-40s: The Vacuum Tube Age

Описание:

By the 1940s, the more portable vacuum tube was introduced. Supposedly invented by Earl C. Hanson, he called his hearing aid the “Vactuphone.” This hearing aid technology was able to address more severe hearing loss. However, they required two batteries, so costs were rather high at the time. Vacuum tubes became smaller but remained awkward over the next decade until transistors appeared.