CRT Video Display

This web page is associated with a book called called The Animated Computer

The book can be bought at: https://play.google.com/store/books/details/Dr_Jerome_Heath_THE_EBOOK_ON_COMPUTER_DESIGN?id=WxOTBQAAQBAJ

The book gives excellent explanations for the animated images on this web site. This web page shows the animation of the computer designs in action. The book gives explanations of what the animations are about. Combining the books explanations with the animation provides a well rounded understanding of the animated computer.

TV Monitor or Cathode Ray Tube (CRT) Style of Video Presentation

The oscilloscope was the basis for television. The oscilloscope did not make a picture but presented a trace. You sent a signal in and then tuned the cycle of the oscilloscope until the signal stabilized. That meant the oscilloscope was cycling at the same rate as the signal.

Oscilloscope Trace

Television uses a cycle that produces not one but a huge number of traces on the screen in a series. The signal coming in tells the tuner how bright each particular spot on the trace should be (at each point of each trace), not how it curves up and down on the screen. Each trace is straight across the screen. The TV screen of this kind is called a Cathode Ray Tube (CRT).

The Workings of a CRT

A Mock trace of a CRT screen:

This shows (roughly) how the picture is built up in traces.

Television started out in black and white but they ultimately switched to color television. For each spot on the black and white screen the colored television had three: one red, one green, one blue phosphor.

The CRT type screen is becoming rare. When I have looked at screens they have the various flat screens but no CRTs. Someone that I know has a huge CRT type screen that is perhaps 50 inches and almost flat. But the front, picture area, is out from the wall by several feet. I think the CRT, or monitor style screen, is becoming a dinosaur.

The economics of the issue is that once flat screens are competitive with CRTs the flat screen would be chosen because it is far better as a piece of furniture and the picture is better looking. With computers the CRT is just too awkward. If the flat screen is cheaper than a CRT then there is only one choice.

The CRT display actually looks like this when it is run slowly (with a wider than usual trace for visualization):

The screen is updated one line at a time

Dr. Jerome Heath