Computers Are
Your Future
© 2005 Prentice-Hall, Inc.
Computers Are Your Future Chapter 8
Computers Are Your Future
Chapter 8
Wired and Wireless Communication
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
What You Will Learn About
 The limitations of the public switched telephone network
(PSTN) for sending and receiving computer data
 Multiplexing and digital telephony
 Wireless transmission media
 How convergence is blurring the boundaries among popular
communication devices
 Home networking using wired and wireless communications
applications
 Teleconferencing and videoconferencing technology
 Telecommuting and workgroup computing
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Connectivity
 Connectivity is the ability to link various media and
devices.
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Wired Communication via the PSTN
 The public switched telephone network (PSTN) is
the world telephone system.
 It is used for data as well as voice communications.
 Twisted-pair wire and fiber-optic cable provide the
connections for the system.
 Home and business phones are connected to subscriber
loop carriers (SLCs).
 The area serviced by SLCs is called the local loop.
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Multiplexing
 Multiplexing technology enables simultaneous multiuse of transmission lines.
 Copper wire allows up to 24 simultaneous calls per wire.
 Fiber-optic cable permits up to 43,384 calls per strand.
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Last Mile Technologies
 The “last mile” refers to the phone lines that connect
homes and businesses to the local loop.
 The inability of users to access the high-speed fiber-optic
cable creates a bottleneck of data called the last mile
problem.
 Digital telephony technologies that use twisted-pair
wire are referred to as last mile technologies.
 ISDN
 DSL
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Wireless Transmission Media
Microwave
Radio
Infrared
 Wireless transmission media refers to the methods
of carrying data through the air or space using
infrared, radio, or microwave signals.
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Infrared
 Infrared is a wireless transmission medium that
carries data via light beams.
 Transmitter and receiver must be in line of sight.
 An IrDa port is needed to use infrared with a computer.
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Radio
 Radio is a wireless transmission medium that carries
data via radio frequency signals.
 Wireless LANs in a home or business are one type of radio
technology.
 Radio signals can be long range (between cities or regions)
and short range (within a building).
 Radio signals are susceptible to noise and electrical
interference.
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Computers Are Your Future Chapter 8
Microwaves
 Microwaves are high-frequency radio waves.
 Much of long-distance telephone service is carried by
microwaves.
 Microwaves travel in a straight line.
 Microwave relay stations are built about 30 miles apart.
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Computers Are Your Future Chapter 8
Satellites
 Satellites are microwave relay stations suspended in
space.
 They are positioned in geosynchronous orbits.
 Satellites use microwave signals to transmit data to
and from earth-based microwave relay stations.
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Computers Are Your Future Chapter 8
Cellular Telephones
 Cellular telephones enable calls to be placed through
a wireless telecommunications system.
Cellular phones use radio or infrared signals.
Cells are limited geographic transmission areas.
 A mobile telephone switching office (MTSO)
monitors the signal strength of cellular phones.
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Computers Are Your Future Chapter 8
Personal Communication Service (PCS)
 Personal Communication Service (PCS) refers to
digital cellular telephone service technologies.
 Digital cellular phones offer:
 Noise-free sound
 Improved coverage
 Protection from eavesdropping and phone fraud
 Voice recognition
 High-speed Internet access
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Computers Are Your Future Chapter 8
Pagers
 Pagers work like a simple radio.
 Pagers are:
 Constantly listening for a specific signal from a transmitter
 Either one-way (only receive signals) or two-way (send and
receive signals)
 Declining in use due to the increase in cell phone use
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Web-Enabled Devices
 A web-enabled device is any device that can display
and respond to HTML or XML.
 PDAs, cell phones, and tablet PCs are web-enabled
devices.
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Computers Are Your Future Chapter 8
Facsimile (Fax) Transmission
 Fax transmission is the means of sending an image of
a document over telephone lines.
 Fax modems support fax as well as data protocols.
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Computers Are Your Future Chapter 8
TV Internet Set-Tops
 Internet TV is an Internet service that uses a TV to:
 Broadcast TV programs
 Send and receive e-mail
 Access Web sites
 Navigate the Internet using a remote control
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Computers Are Your Future Chapter 8
Wired and Wireless Home Networks
 Wired home networks use coaxial cable, telephone
wires, cat-5 wires, or the home’s electric power
wiring.
 Wireless home networks use radio signals.
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Computers Are Your Future Chapter 8
Wired and Wireless Applications
 Teleconferencing:
 It is the simplest wired application for voice
communication.
 A telephone is used to conduct a conference between more
than two people who are separated by a distance.
 Videoconferencing:
 Two or more people can have a face-to-face meeting when
they are geographically separated.
 Cameras, a computer, and videoconferencing software are
used to conduct the conference.
© 2005 Prentice-Hall, Inc
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Computers Are Your Future Chapter 8
Wired and Wireless Applications
 Telecommuting:
 Telecommuting is performing work at home while being
linked to the office by telecommunications-equipped
computers.
 The advantages of telecommuting include not having to
commute, flexible hours, more family time, and familiar
surroundings.
 Workgroup Computing:
 A workgroup is a group of individuals, working together on
a task, who are able to communicate and collaborate by
way of computers connected to a network.
 Groupware software is used by workgroups.
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