Electronic images made by recording signals on an oscilloscope screen, often with a camera. Ben Laposky and Herbert W. Franke made some of the first electronic art this way in the 1950s.
So we have the artistic advancements of analog computer graphics from Mary Ellen Bute and Ben Laposky with their work with oscillographs.
Peter Bauman, Georg Bak on the Analog Era: 1950s Art