408 Electronic Communication and Data Systems
The FCC’s approval in 1996 of a digital television
standard was the first step toward an improved and a
higher quality picture. Although the switch to digital has
progressed slowly, with more and more television stations
switching to digital broadcasts and many digital television
formats emerging, high definition television (HDTV) has
become the dominant digital television technology.
HDTV allows for higher resolutions and a wider dis-
play screen than an analog display system. HDTV uses
digital broadcasting techniques, allowing more informa-
tion-rich data to be transmitted by airwaves than by ana-
log broadcasts. Digital broadcasting can broadcast multi-
ple channels in the same bandwidth as that used for one
analog channel. Broadcasting multiple channels is
referred to as multicasting. Multicasting allows not only
for the image to be broadcast, but also for two to four
channels to be broadcast in the same single-channel
bandwidth. The additional channels can be used to trans-
mit additional images, resulting in “picture-in-picture”
and information such as stock prices, weather reports,
sports scores, or background information about the actors
in the movie being viewed. Any information found on the
Internet can be incorporated into the display screen.
When additional information is transmitted along with
the video image, it is referred to as datacasting. You will
soon likely be able to integrate a digital camera into the
system so that you can see the baby sleeping in the next
room while watching your favorite television show.
To be considered a complete HDTV system, three
major system components are required, Figure 23-34:
• A digital camera to record the images at the higher
resolution.
• A digital receiver (HDTV tuner) to convert received
broadcasts into image and sound.
• A display unit capable of producing images at the
high definition TV resolution.
If any of the three major parts are missing, the
HDTV system is incomplete and will not produce an
HDTV picture. There are many television variations that
Figure 23-34. Major components required for a
complete HDTV system.
Captured light
from an image
Photo sensor
Level of
electrical charge
Storage
device
Memory
Broadcast
CCD Array
Analog Digital
Analog-to-digital
converter
Figure 23-35. A CCD as it captures an image.