How a CRT Television Works

Billions of people all over the world enjoy television. A few years ago the most common type of TV was the cathode ray tube (CRT) TV. This is where television got its nickname, 'the tube'. Since then, the technology has become more advanced and liquid crystal display (LCD) and plasma TVs have come into play. For now, though, we will be sticking to the CRT TV and how it works.

The Brain
Just like many other things in this world, TV would not be possible without two amazing powers of the brain. The first thing that is required to watch TV is something I call 'dot assembling'. When you see an image, made up of many small dots (in this case, pixels), the brain will assemble those little specks into a clear image.
The second power that the brain has is the ability to put together a series of images, each slightly different than the last, into a moving picture. Both of these powers work together to allow you to watch TV.

The Cathode Ray Tube
The CRT starts with a heated filament, similar to one in a light bulb. A stream of electrons is produced naturally. Next comes the anode, which both focuses and accelerates the stream of electrons. The stream is now aimed directly at the outer screen of the CRT.

Moving the Stream
Inside the TV, behind the CRT, is a pair of electromagnets. These react with the stream to move it sideways and up and down. The stream can be moved to anywhere on the screen.

Making the Picture
To start making the picture, the stream of electrons is moved to the top left corner of the screen. The outer screen of the CRT is coated in phosphor, and when the electrons hit it, the phosphor glows. This is then projected onto the TV screen. The electromagnets move the electrons across the screen, 'painting a picture'. The picture is painted line by lines, 60 times a second. To make the different variations between black, white and gray, the stream of electrons is intensified by increasing the voltage. To make white, the voltage goes on at full blast. To create black, the voltage is turned off when the stream scans by.

Color CRT TV

A color TV is very similar to a black and white TV, structurally. There are just a few differences. There are three electron streams, instead of one. The colors of the streams are red, green and blue. Also, the phosphor coating on the screen is three colors, red, green and blue, arranged in dots or stripes. Lastly, there is a thin sheet of metal that has very small holes in it, aligned with the phosphor dots. Every color is made of some combination of red, green and blue.