Pen-Based Systems
An application of passive matrix LCD technology is the portable pen-based computer,
a.k.a. the personal digital assistant (PDA) or palmtop computer. Although it may also
have a keyboard, commands and data are entered through the screen with a special
nonwriting pen or stylus.
The display is covered by a protective plastic covering and beneath the display is a
mechanism to recognize the movements of the stylus. A wire grid is placed beneath the
display that records the movements of the pen over the grid’s intersections, which is similar
to the technology behind touch-screens.Monitor Power
Monitors do not run off the PC’s power supply. Even in the days when the monitor’s power
cord could plug into the back of the PC’s power supply, the plug it used was an AC power
pass-through plug. A PC monitor uses more power than all of the other components of the
PC added together, with the possible exception of some laser printers. Because of how it
works, several power issues exist on monitors that don’t exist on a PC or its power supply.Power Management
In an effort to reduce the tremendous amount of energy being consumed by monitors in
active mode, one government initiative and one industry initiative emerged to try to
reduce the power consumption of PC monitors when they are idle.
The U.S. Environmental Protection Agency (EPA) developed a program called Energy
Star that certifies monitor (and personal computers) that meet the guidelines for re-
duced energy consumption. This program is also called the Green Standard and the
computers that meet the standard are calledgreen PCs. The Energy Star program certifies
monitors that use less than 30 watts of power in all power modes and reduce their power
consumption by 99 percent when in sleep or suspended mode. Most PCs sold today meet
this standard; you will see the Energy Star logo displayed on the monitor during the boot
sequence on those PCs that comply.
Virtually all monitors on the market today are also compliant with VESA’s Display
Power Management System (DPMS) protocol. DPMS is used to power down parts of the
monitor and PC after they have been idle for a certain period of time. DPMS is a
BIOS-supported protocol that can be enabled in the CMOS settings of the PC.Degaussing
Over time, the internal components of a CRT become magnetized and can have a nega-
tive impact on the image quality of the monitor. If the CRT becomes overly magnetized,
the display can develop color blotches near the edges and especially in the corners. There
are lots of ways that the CRT can be magnetized, including having a set of stereo speakers(^396) PC Hardware: A Beginner’s Guide