File:Lieben-Reisz vacuum tube.jpg

English: A "Lieben-Reisz tube" (or "Lieben-Reisz-Strauss relay"), an early experimental amplifying vacuum tube developed by Austrian engineers Robert von Lieben and Eugen Reisz beginning in 1906 and a competitor to the Audion (triode) invented by Lee De Forest for the earliest amplifying vacuum tube. About 16 in (41 cm) tall and 4 in (10 cm) wide.

It consisted of a partially evacuated glass envelope containing 3 electrodes: a heated platinum filament wire (bottom) coated with barium or calcium oxides which released electrons which were attracted to the positively charged anode wire (top), passing through a "grid" made of a perforated metal plate (center). As in the Audion, a small voltage on the grid could control a larger anode current, so the tube could amplify. The inventors claimed a voltage gain of 33. The tube had a small amount of mercury vapor in it, released by the pellet of mercury amalgam in the small U shaped tube on the lower left side, to reduce the high anode voltage of 220 V required when the tube was evacuated.

These were used by Alexander Meissner in 1913 to build some of the first electronic oscillator circuits, which he used the same year in a historic radiotelephone experiment, transmitting 500 kHz AM voice signals 23 miles (36 km) from Berlin to Nauen, Germany. Since the tube was patented a few months before the Audion, Lieben sued De Forest for patent infringement, but ultimately lost due to the deep pockets backing the Audion. (Information from source text)