<P> This simple design is effective and cheap to build, but it wastes some power continuously . Later models, especially Energy Star rated ones, use a relay to switch the entire degaussing circuit on and off, so that the degaussing circuit uses energy only when it is functionally active and needed . The relay design also enables degaussing on user demand through the unit's front panel controls, without switching the unit off and on again . This relay can often be heard clicking off at the end of the degaussing cycle a few seconds after the monitor is turned on, and on and off during a manually initiated degaussing cycle . </P> <P> Vector monitors were used in early computer aided design systems and are in some late - 1970s to mid-1980s arcade games such as Asteroids . They draw graphics point - to - point, rather than scanning a raster . Either monochrome or color CRTs can be used in vector displays, and the essential principles of CRT design and operation are the same for either type of display; the main difference is in the beam deflection patterns and circuits . </P> <P> Dot pitch defines the maximum resolution of the display, assuming delta - gun CRTs . In these, as the scanned resolution approaches the dot pitch resolution, moiré appears, as the detail being displayed is finer than what the shadow mask can render . Aperture grille monitors do not suffer from vertical moiré; however, because their phosphor stripes have no vertical detail . In smaller CRTs, these strips maintain position by themselves, but larger aperture - grille CRTs require one or two crosswise (horizontal) support strips . </P> <P> CRTs have a pronounced triode characteristic, which results in significant gamma (a nonlinear relationship in an electron gun between applied video voltage and beam intensity). </P>

Why do crt monitors have holes in the top of the case