three electron guns to correct most problems. Some group-oriented systems use PC monitors as opposed to television monitors. PC monitors are evaluated according to their Video and Electronics Standards Association (VESA) rating. There are four standard VESA resolutions. These are VGA 640H X 480V; Super VGA (or SVGA) 800H X 600V; and two XGA resolutions: 1,024H X 768V and 1,280H X 1,024V. Some monitors even go higher, to resolve an image at 1,800H X 1,440V. The ultrahigh resolutions primarily suit professional-level work in fields such as desktop publishing and computer-aided design, not video communication (for which SVGA delivers an excellent image). Given the advantage of the smaller footprint, most people today will choose to buy a flat-screen monitor rather than a CRT. These come in two general types, LCD and plasma, each of which offers its own advantages and disadvantages. The advantages of plasma over LCD include larger screen size, deeper blacks, and superior contrast and motion tracking. However, plasma is more susceptible to burn- in, generates more heat, offers a shorter life span, and is unreliable at higher altitudes. In contrast, LCD monitors require no burn-in, run cooler, last longer, and do not suffer from high altitude issues. Unfortunately, LCD monitors offer lower contrast ratio, grayer blacks, inferior motion tracking, and pixel burnout (which results in small black or white dots on the screen). Picture-in-Picture Although it is not really a monitor feature (it is a system feature), picture-in-picture (PIP) is an important in single monitor systems. Also known as quadrant display or windowing, PIP relies on a codec's receive circuitry to create and send two images to a monitor. One image occupies most of the screen except for a small corner where the second image, smaller but complete, can be inserted in a window. The window can be closed when it is not needed. PIP provides a mechanism for monitoring near-end image capture in single monitor systems. Continuous Presence Like picture-in-picture