cathode-ray tuning indicator

cathode-ray tuning indicator

[′kath‚ōd ¦rā ′tün·iŋ in·də′kād·ər]
(electronics)
A small cathode-ray tube having a fluorescent pattern whose size varies with the voltage applied to the grid; used in radio receivers to indicate accuracy of tuning and as a modulation indicator in some tape recorders. Also known as electric eye; electron-ray indicator; magic eye; tuning eye.