SHEILA TERRY / SCIENCE PHOTO LIBRARY SHEILA TERRY / SCIENCE PHOTO LIBRARY
Audion amplifier. Diagram of an Audion triode valve that was the first amplifier. It was invented by Lee De Forest in 1907. De Forest worked on vacuum tubes, which act as diodes (devices that allow electricity to flow one way only). The addition of a grid (yellow) allowed the amplification of weak radio signals (top), which made radio a practical method of transmitting information.
Model release not required. Property release not required.