nuvistor

thumb|right|upright|RCA 6DS4 "Nuvistor" triode vacuum tube, ca. 20 mm high and 11 mm in diameter thumb|upright|right|Nuvistor with U.S. dime for scale

The nuvistor is a type of vacuum tube announced by RCA in 1959. Nuvistors were made to compete with the then-new bipolar junction transistors, and were much smaller than conventional tubes of the day, almost approaching the compactness of early discrete transistor casings. Due to their small size, there was no space to include a vacuum fitting to evacuate the tube; instead, nuvistors were assembled and processed in a vacuum chamber by simple robotic devices. The tube envelope is made of metal, with a ceramic base. Triodes and a few tetrodes and pentodes were made; nuvistor tetrodes were taller than triodes.