Setting Up A Screen Saver To Avoid Burned In Image On The CRT
| Field | Computers |
| Went Obsolete | 1993 and approximately 2003 |
| Made Obsolete By | The Introduction of DPMS power saving modes and later cheap LCD monitors |
| Knowledge Assumed | How to use a computer |
| When useful | If using an antiquarian mono,CRT or to secure a system |
All Cathode ray tubes use an electron gun to light up phosphorus that is on the inside of the tube. If a static image is left on the tube for prolonged periods of time, the monitor can "Burn in". This is caused when the phosphors are depleted due to constant excitation by the electron gun.
Even LCD monitors can end up with "Stuck pixels" if they are left on a static image for too long. Mind you, this is purely temporary and can be resolved by turning the monitor on and off a few times. Whereas "Burn in" on a CRT is permanent.
Each operating system has a unique way of setting up a screensaver. Ever since the early 1960s when CRT terminals were introduced, the most crude of screensavers involved automatically blanking the screen. This was done through DIP switches on the terminal.
In 1993 DPMS was introduced to allow the computer to signal the monitor thorough the H and V Sync lines to enter lower power states after periods of inactivity from the user and to also return to normal modes when various activity was performed. After the introduction of DPMS screensavers were relegated to being used as "screen candy" and no longer served as the main burn-in preventer. One large fault of using a screen saver is that even while displaying a screensaver the CRT is active, using power and constantly exciting the pixel phosphors. Eventually the entire screen dims as the phosphors wear out evenly over the entire screen. Using the DPMS system allowes the CRT to be fully deactivated and greatly increased lifespan and helped maintain the brightness of the display. The DPMS system is still used by LCD panel monitors to further lower energy consumption, and less as a method to prevent burn-in. LCD monitors that use CCFL tubes to light the display will lose brightness over time so DPMS helps extend the lifespan and brightness of the tubes.
Technically, this skill isn't obsolete due to privacy and security concerns as many operating systems allow the display to be "locked" when activating the screensaver. The screensaver is used to hide to contents of the display to increase security and is only deactivated by entering a password or some other form of user identification.