1AH4 is an electron-beam tetrode vacuum tube, which was manufactured by the RCA Victor Company from 1930 until the mid-1960s. It was developed for use in radio and television applications, where it found wide acceptance.
The tube features a cathode, grid, plate, and beam-forming plates electrically connected in a single terminal structure. It was designed to operate at a comparatively high temperature and low current, giving it exceptional operating characteristics compared to other vacuum tubes.
The tube is often associated with the creation of broadcast-quality sound and video. It was used extensively in television receivers and programming, as well as in transmitters used in AM and FM radio broadcasts. Due to its robustness and high-quality performance, the 1AH4 was often incorporated in aesthetically pleasing sets, such as Harmon-Kardon's combination television-audio sets.