Electronic Communications

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Chapter 11

• Electronic Communications

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Understanding Communication Systems

• Key ideas
• Information and communication technologies
  include the inputs, processes, and outputs
  associated with sending and receiving
  information.
• Information and communication systems allow
  information to be transferred from human to
  human, human to machine, machine to human, and
  machine to machine.

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Understanding Communication Systems (contd.)

• Key ideas (contd.)
• 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.

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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

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Communication Systems (contd.)
Figure 11.5 Communication process consists of a
source, encoder, transmitter, receiver, decoder,
storage, retrieval, and destination.
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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.

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Identifying Types of Communications (contd.)

• Key ideas (contd.)
• Graphical analysis and presentation can be
  divided into two general types qualitative and
  quantitative.
• 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).

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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 messages.

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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

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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.

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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
  receiver.

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Defining Telecommunications (contd.)

• Key ideas (contd.)
• Communication technology and the ability to
  communicate electronically provide a competitive
  advantage.
• 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.

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Telecommunications

• 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 CNN.com) to new media
(such as blogs).
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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.
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Telecommunications (contd.)

• 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).

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Telecommunications (contd.)

• Basic elements
• All communication systems can be modeled with the
  core components (transmitter, media, receiver).
• Transceiver
• Transmitter and receiver

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Analog Versus Digital
Figure 11.25 If you move a garden hose slowly up
and down, the water stream shows low-frequency
peaks.
Figure 11.29 You can use the stream from the hose
to simulate binary 1s and 0s.
Figure 11.26 By moving the hose faster, you
create waves of higher frequency.
Figure 11.31 The difference between an analog
signal and a digital signal is dramatic.
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Channels

• 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

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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.
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Satellite Communications

• Key ideas
• In communications, a satellite is a manmade
  object positioned in the Earths 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.

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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 satellites onboard
  clock, selective availability, and relativistic
  errors.

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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

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Figure 11.41 Various types of orbits include
geosynchronous, medium Earth, and low Earth
orbits.
Figure 11.42 Satellite orbits can be polar, high
incline, or low incline.
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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

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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.
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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).

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Exploring Digital Media (contd.)

• Key ideas (contd.)
• 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 created.
• 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.

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Exploring Digital Media (contd.)

• Key ideas (contd.)
• 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.

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Exploring Digital Media (contd.)

• Most devices are built around the same basic
  process
• 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.

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Exploring Digital Media (contd.)

• 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.