- Up until recently, CRTs (Cathode RayTubes) were the only type
of displays for use with desktop PCs. They are relatively big
(14" to 16" deep) and heavy (over 15 lbs).
- They are available in screen sizes from 14" to 21". A
17" display means that it is 17" measured diagonally from
one corner of the tube to the other. The actual viewing
area is smaller than 17" (about 16") since the electron gun
can't sweep completely to the tube edge.
- CRTs send a stream of electrons at the screen, which is
charged to about 25,000 volts. As they strike it they cause
phosphor on the backside of the screen to glow creating
light which you see. The electron stream is sweep back and
forth and up and down at about 60 sweeps per second and
turned off and on at the right time to make text and
graphics images appear.
- They are powered by standard 120Vac wall power.
- Data is transferred to the display on a cable with a
15-pin D-shell connector that plugs into a connector on the
video card which in turn plugs into one of the PC's
expansion slots.
- A 17" monitor with 1280 x 1024 resolution and .27mm dot pitch sells for around $150.
LCD Monitors
- Liquid Crystal Display (LCD) technology has been used in laptops for
some time. It has recently been made commercially available as monitors
for desktop PCs.
- LCDs have no electron gun and are therefore not very deep like
CRTs. The text and images you see are created by a back light behind the
panel, that shines through pixels (picture elements). Each pixel is
made up of three chambers red, green and blue. The chambers in each
pixel must be opened enough and in the proper proportion to produce the
correct brightness and color.
- For an LCD to provide a screen resolution 1024 x 768 pixels
(SVGA), it must have 786,432 (1024 x 768) pixels. In TFT (Thin Film
Transistor) type LCDs, each pixel is controlled by a tiny transistor
that opens and closes the chambers in each pixel.
- Desk top LCD displays are powered by standard 120Vac wall power.
- Data is transferred to the display on a cable with a 15-pin
connector that plugs into a mating connector on the video card seated in
an expansion slot in the PC.
- A 17" LCD monitor with 1280 x 1024 resolution and .27mm dot pitch sells for around $500.
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