Television cameras break a picture into electrical signals, separating them into three colours (red, blue and green) and turning them into coded messages. Sound is recorded and coded at the same time. The coded pictures and sounds are transmitted by radio waves, electrical cables or optical fibres to the receiver. Inside a television receiver the signals travel to three electron guns — one for each colour. The electron guns emit streams of electrons, which are directed at a fluorescent screen. Magnets bend the electron streams so that they scan back and forth from top to bottom, exciting the phosphors in the screen and producing a colour image. They scan so quickly that our eyes see the images as a continuous picture.
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