As far as electronics is concerned, the term video was originally used to describe the "picture" signal, which modulated a RF carrier for television in the 1920's. When this signal was detected and applied to a scanning CRT, a picture was produced. During World War II, video was the term applied to the detected RF pulse received by the radar, as the pulse could be seen on the radar CRT. At that time, oscillographs (oscilloscopes) could not display RF signals. A crystal detector was used to rectify the RF and produce an envelope of the RF signal, which could be displayed by the oscillograph. So, video is also the term applied to the detected RF from a crystal detector. The term video is also used to describe the signal, which modulates a RF carrier.