Lee de Forest

Making a signal easier to control

De Forest pursued electrical research at Yale and entered wireless work at a time when most radio traffic was sent in code. A receiving station needed a way to detect a weak signal. He experimented with tubes in which current passed between electrodes, then explored how a third electrode could influence that current. The Audion was associated with this work.

A surviving experimental tube and a patent answer different questions. The tube allows a museum to identify a physical arrangement. The patent records the apparatus and use the inventor asked to protect. Neither gives a complete account of how later engineers turned the device into a dependable amplifier.

Sources for this section: [1] · [2] · [3]

Inventing a component and designing a circuit

Armstrong’s experimental detector includes a De Forest tube. In that assembly the tube works with a larger network that returns part of the signal. The record lets us attribute the tube and the circuit relationship separately. That is useful in reading a history full of overlapping devices and disputes about priority.

De Forest promoted uses for radio beyond point-to-point signaling and tried to turn demonstrations into a business. The project involved a market for equipment and a reason for people to receive a programme, questions that the tube itself could never settle.

Sources for this section: [1] · [4]

Carrying sound with a picture

His later Phonofilm work pursued sound with moving pictures. It posed another timing problem: a picture and a voice had to stay aligned during exhibition. The projects differ in their mechanics, but both give his career a recurring theme. To move sound successfully, an inventor had to decide how to represent it, recover it and put the recovered signal to work in a real setting.

Sources for this section: [1] · [5]