Chapter 11
Electronic Communications
Understanding Communication
• Key ideas:
– Information and communication technologies
include the inputs, processes, and outputs
associated with sending and receiving
– Information and communication systems allow
information to be transferred from human to
human, human to machine, machine to human,
and machine to machine.
Understanding Communication
Systems (cont’d.)
• Key ideas (cont’d.):
– Communication systems are made up of a
source, encoder, transmitter, receiver, decoder,
storage, retrieval, and destination.
– At the source, a modem modulates an analog
carrier signal to encode digital information.
• At the destination or receiver, a modem demodulates
the signal to decode the transmitted information and
receive the message.
Communication Systems
• Made up of building blocks:
– Consider instant messaging
• Input, transmit (process), output, feedback
• Communication process includes:
A source
An encoder
A channel
A decoder
A receiver
Communication Systems (cont’d.)
Figure 11.5 Communication process consists of a source, encoder,
transmitter, receiver, decoder, storage, retrieval, and destination.
Identifying Types of Communications
• Key ideas:
– Information and communication systems can be
used to inform, persuade, entertain, control,
manage, and educate.
– There are many ways to communicate.
– Technological knowledge and processes are
communicated using symbols, measurements,
conventions, icons, graphic images, and
languages that incorporate a variety of visual,
auditory, and tactile stimuli.
Identifying Types of Communications
• Key ideas (cont’d.):
– Graphical analysis and presentation can be
divided into two general types: qualitative and
– Oral presentations to bosses, teachers,
customers, or colleagues at meetings or
conferences can be used to share information, or
sell an idea, a product, or even yourself (for
example, a job interview).
Types of Communications
• How we communicate our message depends
on the communication medium.
– Graphic communications:
• Words and pictures convey a message.
– Electronic communications:
• Electrical signals, pulses of light, or radio waves carry
Graphical Communication
• Technical communication:
– Sharing technical information through graphs,
graphics, and other visual tools.
– Computer-Aided Design programs are used to
create blueprints.
– Qualitative information:
• Drawings, bar graphs, and pie charts
– Quantitative information:
• Tables and line graphs
Oral Communication
• Steps to improve:
– Preparation:
• Jot down facts and create an outline.
• Identify theme.
• Split into 15-20 minute chunks and practice.
– Visual aids:
• PowerPoint/KeyNote.
– Presentation techniques:
• Look presentable, neat, and well dressed
• Speak clearly and loud enough.
Defining Telecommunications
• Key ideas:
– Telecommunications is a very broad term that
implies transmission of messages at a distance
• Could include transmission of signals via smoke
(smoke signals), sound (drums), flags (semaphore),
and even reflected sunlight (heliograph).
– Modern telecommunications involves some
combination of an electronic transmitter and
Defining Telecommunications (cont’d.)
• Key ideas (cont’d.):
– Communication technology and the ability to
communicate electronically provide a competitive
– Digitizing voice data allows telecommunications
carriers to use a single common digital
infrastructure for voice, video, and data.
– A basic communications system consists of:
• A transmitter to send the message, media over which
to send it, and a receiver of the information.
• Telecommunication:
– Ability to connect with voice, video, and data
– Global telecommunications market:
• Three percent of the gross world product
Figure 11.17 Modern communication is shifting from old
media (such as to new media (such as blogs).
Figure 11.21 The developing world lags
behind the rest of the world in fixed
telephone use.
Figure 11.22 Internet access is also
less frequent in the developing world
than in other countries.
Telecommunications (cont’d.)
• Telegraphy:
– Transmission of messages as a series of dots and
dashes (i.e., Morse code).
• Replaced with telephony (Bell and Gray).
• Telephony:
– Switchboard
• Switches established a connection.
– Analog
• Public Switched Telephone Network (PSTN) dominant
protocol is Asynchronous Transfer Mode (ATM).
Telecommunications (cont’d.)
• Basic elements:
– All communication systems can be modeled with
the core components (transmitter, media,
– Transceiver:
• Transmitter and receiver
Analog Versus Digital
Figure 11.25 If you move a garden hose
slowly up and down, the water stream
shows low-frequency peaks.
Figure 11.26 By moving the hose faster,
you create waves of higher frequency.
Figure 11.29 You can use the stream from
the hose to simulate binary 1s and 0s.
Figure 11.31 The difference between an
analog signal and a digital signal is
• Each network or station broadcasts its own
signal in a very specific communications
channel, usually associated with a frequency
– Frequency division multiplexing:
• Multiplex: bundled channels together
• Demultiplex: unbundle channels after receiving them
– Time division multiplexing:
• “Chop” time into slices or slots and assign each
conversation its own time slot
Carrier Waves
• Carrier waves:
– Analog signal or
waveform acts
as a carrier.
• Modulation:
– How the signal
is carried.
Figure 11.36 In frequency modulation (FM),
the frequency of the carrier wave is modified.
Satellite Communications
• Key ideas:
– In communications, a satellite is a manmade
object positioned in the Earth’s orbit to facilitate
communication on the Earth.
• A satellite usually travels in either a geostationary,
elliptical, or low Earth orbit (LEO).
– A satellite constellation is a group of satellites
working together.
Global Positioning Systems
• Key ideas:
– The Global Positioning System (GPS) uses a
constellation of at least twenty-four medium
Earth orbit satellites to transmit microwave
signals to a GPS receiver.
– Civilian GPS is only accurate within 15 meters
because of a combination of factors:
• Errors due to atmospheric conditions, multipath
effects, clock drift in the satellite’s onboard clock,
selective availability, and relativistic errors.
Satellite Communications
• Satellite:
– Celestial body orbiting Earth or other planet
– Usually categorized by their orbits (e.g.
geostationary, elliptical, or low Earth orbits)
• Sputnik I
• Explorer I
– Variety of applications
– Satellite constellation:
• A group of satellites working together
Figure 11.41 Various types of
orbits include geosynchronous,
medium Earth, and low Earth
Figure 11.42 Satellite orbits
can be polar, high incline,
or low incline.
Global Positioning Systems
• Enables a user to accurately determine
location, speed, direction, and time
– Receiver identifies satellites within range and
calculates its position relative to three or more
of them
Figure 11.45 A constellation of satellites helps
to operate the Global Positioning System.
Figure 11.46 Atmospheric effects and
errors have the greatest effect
on GPS accuracy when satellites are
near the horizon.
Exploring Digital Media
• Key ideas:
– The shift from analog to digital information has
forever altered the way we view sound, images,
and video, and has opened up entirely new
methods of communication and connectivity.
– Digital media is made up of ones and zeroes,
and is measured in bits, bytes (8 bits), kilobytes
(103 or 1,000 bytes), megabytes (106 or
1,000,000 bytes), and gigabytes (109 or
1,000,000,000 bytes or 1,000 megabytes).
Exploring Digital Media (cont’d.)
• Key ideas (cont’d.):
– With analog media, we record sound by
“scratching” an analog signal, created by your
voice or a musical instrument, onto a surface
and playing it back following the grooves we
– The MP3 file format uses a compression
algorithm to reduce the size of a song while
retaining near-CD sound quality, compressing a
32-MB song to 3 MB.
Exploring Digital Media (cont’d.)
• Key ideas (cont’d.):
– Digital cameras and camcorders function by
focusing light onto a small semiconductor image
sensor that filters the light into the three primary
colors, records the colors, and combines them to
create a full-color image.
Exploring Digital Media (cont’d.)
• Most devices are built around the same basic
– Converting analog into digital information
• ADC (analog-to-digital converter)
• DAC (digital-to-analog converter)
• Digital media is made up of ones and zeroes
– When we refer to digital media, we refer to bits,
bytes, kilobytes, megabytes, and gigabytes.
Exploring Digital Media (cont’d.)
• Digital media includes:
– Audio, images, video
– Digital cameras and camcorders focus light onto
a small semiconductor image sensor
• Often, this sensor is a charge-coupled device (CCD)
• CCD consists of a 1-cm panel of hundreds of
thousands of light-sensitive diodes called photosites
• High-end cameras and camcorders use three sensors,
as well as three filters with a beam splitter to direct
light to the different sensors.

Chapter 11