Lecture Computing for management - Chapter 5

Lecture 5
Video and Sound


Summary of Previous


We have learnt,
 Reasons

why some computer users prefer alternative
methods of input over a standard keyboard or mouse.
 Input data by touch
 Game controllers
 Input data by light
 Other input types, e.g. audio, video etc.
 When to use which input device?
 Practical


Today’s Topics
Monitors
 Monitors and Video Cards
 Video Cards
 Ergonomics and Monitors
 Data Projectors
 Sound Systems



Multimedia



The word ‘multimedia’ comes from the
Latin word multus means ‘numerous’ and
media which means ‘middle’ or Centre.



Multimedia consists a large number of
visual media like graphics, image,
animation etc


Visual Display Devices


Primary user hardware for displaying visual
media such as graphics, text, images.



Consists of components such as Monitor, Video
adapter card, video adapter cable.



Various such devices are CRT, color CRT,
DVST, Flat Panel Displays (LCD & Plasma),
LED monitors, etc.

Monitor
It is a most common output device
 A monitor or display (also called screen
or visual display unit) is an electronic
visual display for computers.
 Originally, computer monitors were used
for data processing while television
receivers were used for entertainment.



Monitor


Monitor


Quality of picture we see on monitor
depends upon,
 Monitor

quality itself
 Video controller.


From the 1980s onwards, computers (and
their monitors) have been used for both
data processing and entertainment.

Technologies







Different image technique have been used for
computer monitors.
Until the 21st century most monitors were CRT
but they have been phased out for LCD
monitors.
They are categorized by color output.
Monitors connects to the video card of a
computer system.


Monitors Types


Different types of monitors exists, which
are;
 Monochrome
 Grayscale
 Color

10

Monochrome Monitor


A monochrome monitor is a type of CRT computer
display which was very common in the early days of
computing.






From the 1960s through the 1980s, before color monitors
became popular.

They are still widely used in applications such as
computerized cash register systems.
Green screen was the common name for a
monochrome monitor.
They are abandoned in early-to-mid 1980’s.


Monochrome Monitor


Grayscale Monitors






A special type of monochrome monitor capable
of displaying different shades of gray.
They are also known as black-and-white, are
composed exclusively of shades of gray, varying
from black at the weakest intensity to white at
the strongest.
Early grayscale monitors can only show up to
sixteen different shades


Grayscale Monitor


Color Monitors






A display monitor capable of displaying many colors.
Color Monitors works like a monochrome one, except
that there are three electron beams instead of one.
The three guns represent additive colors (red, green and
blue) although the beam they emit are colorless.
Each pixel includes three phosphors, red, green and
blue, arranged in a triangle.

When the beam of each of these guns are combined and
focused on a pixel, the phosphors light up.


Color Monitors


The monitors can display different colors by combining
various intensities of three beams.


Mixing of Colors


What is being used today?



The most popular display today remains
Color monitors CRT.
It has been available for more than 70 years.
CRT is used.



Cost less than LCD monitors.





History of the Cathode Ray










1855- Heinrich Geissler creates the mercury pump, the first good
vacuum tubes. Sir William Crookes uses these to produce the first
cathode rays.
1858- Julius Plücker bends cathode rays using a magnet
1869- J.W. Hittorf establishes that the “rays” travel in straight lines
1883- Heinrich Hertz concludes incorrectly that cathode rays are not
made up of particles because they are not deflected by electrically
charged metal plates
1895- Jean-Baptiste Perrin shows that cathode rays are particles
because they deposit a negative charge where they impact
1897- J.J. Thomson discovers electrons using cathode rays


How Monitor Works?
Most use a cathode-ray tube as a display
device.
 CRT: Glass tube that is narrow at one end

and opens to a flat screen at the other
end.



How Monitor Works?






Electrons travel through a vacuum sealed
container from the cathode (negative) to the
anode (positive).
Because the electrons are negatively charged,
they are repelled away from the cathode, and
move across the tube to the anode.
The ray can be affected by a magnet because of
its relation to positive and negative charges


Some Anatomy of the CRT



Anode- Positively Charged, Ray travels towards this
Cathode- Negatively Charged, Ray travels away from
this

Cathode Ray Tube (CRT) Monitors


A CRT monitor contains millions of tiny red, green, and
blue phosphor dots that glow when struck by an electron
beam. Electron beam travels across the screen to create
a visible image.



In a CRT monitor tube, the cathode is a heated filament.



The heated filament is in a vacuum created inside a
glass tube. The electrons are negative and the screen
gives a positive charge so the screen glows.


Basic Cathode Ray Tube






Electrons excite phosphor to glow
Electrons fired from the back
Phosphor is arranged in dots called pixels

Dot mask ensures proper pixel is lit


Phosphore




It is a semi-conducteur material which emits visible
radiation in response to the impact of electrons.
(i.e. when it absorbs energy from some source such
as an electron beam, it releases a portion of this
energy in the form of light).
In response to a sudden change in the electron
beam(from on to off), the light emission does not fall
instantaneously, there is a gradual reduction challed
‘fluorescence’ .