What is the operating principle of a TV transmitter?

To convert images of objects into electrical signals, the lens of a television camera will create an image on the screen of the transmitting tube. Under the influence of light, electrons are ejected from the surface of the screen, the surface of the screen acquires a positive charge. The charges of different parts of the screen are determined by the picture of the light image. The electron beam runs over the screen of the transmitting tube 625 times in 1/25 of a second. When the beam moves along the screen of the transmitting tube, the current in the screen circuit changes in accordance with the electric charge accumulated on each element of the screen. These current changes are used to modulate the signal.