What is "phonovision"

Phonovision is a proof of concept format and experiment for recording a mechanical television signal on gramophone records. The format was developed in the late 1920s in London by Scottish television pioneer John Logie Baird. The objective was not simply to record video, but to record it synchronously, as Baird intended playback from an inexpensive playback device, which he called a "Phonovisor".