Early Valve (1910s) : controlling the flow

This is an early valve that was used in the late 1910s / early 1920s. In the later models the valves lost their roundness and became longer, transparent tubes.

Although valves changed their shape, their essential function remained the same. It worked a lot like an electronic tap regulating the flow of the current passing through it. This means it could reduce a current to pass it on at the correct frequency, or in some cases, a series of valves could work together to boost a current to amplify it as well.

This valve was used for audio and could have been found inside a radio set. A broadcast would be received as radio waves, however they would have to be transformed into audio waves, which have passed through the valve on their way to the speakers