What was “the Audion”?

In 1906, the American inventor Lee de Forest build what he called “the Audion,” which became the basis for the radio amplifying vacuum tube. This devise made voice radio practical, because it magnified the weak signals without distorting them. The next year, de Forest began regular radio broadcasts from Manhattan, New York. As there were still no home radio receivers, de Forest’s only audience was ship wireless operators in New York City Harbor.