A camera tube widely used in television broadcasting. It consists of three sections within a single vacuum envelope. 1
. A photosensitive film sometimes called the photocathode. The scene to be televised is focused on this film by an outside camera lens. 2
. The scanning beam provided by an electron gun scans lines of the target film. The gun's beam is deflected by electromagnets within the tube (the whole picture is scanned by the beam in 1/30 second). 3
. A return beam of electrons falls upon a multiplier section that develops an electron current of sufficient magnitude to be sent out from the broadcast transmitter as a video signal.