The nuvistor is a type of vacuum tube announced by RCA in 1959. Most nuvistors are basically thimble-shaped, but somewhat smaller than a thimble. Triodes and tetrodes were made, although tetrode nuvistors are rare. The tube is made entirely of metal and ceramic. Making nuvistors requires special equipment, since there's no intubation to pump gases out of the envelope. Instead, the entire structure is assembled, inserted into its metal envelope, sealed and processed in a large vacuum chamber wit… (More on Nuvistor)