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Using Information Technology. Chapter 7 Telecommunications. Telecommunications Networks & Communications--The “New Story” in Computing. 7.1From the Analog to the Digital Age 7.2The Practical Uses of Communications 7.3Communications Channels: The Conduits of Communications

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Using information technology l.jpg

Using Information Technology

Chapter 7

Telecommunications


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TelecommunicationsNetworks & Communications--The “New Story” in Computing

  • 7.1From the Analog to the Digital Age

  • 7.2The Practical Uses of Communications

  • 7.3Communications Channels: The Conduits of Communications

  • 7.4Factors Affecting How Data Is Transmitted

  • .

  • .

  • .

Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.


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Networks & Communications--The “New Story” in Computing

  • 7.5Networks

  • 7.6The Future of Communications

  • 7.7Cyberethics: Controversial Material, Privacy, & Intellectual Property

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7.1 From the Analog to the Digital Age

  • Analog - continuous and varying in strength and/or quality

  • Digital - communications signals or information represented in a two-stat (binary) way

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Purpose of the Modem: Converting Digital Signals to Analog Signals & Back

Modem - short for modulate/demodulate

  • Sending modem - modulates digital signals into analog signals for transmission over phone lines

Receiving modem - demodulates the analog signals back into digital signals

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7.2 The Practical Uses of CommunicationsVideoconferencing & Videophones

  • Videoconferencing - the use of television video and sound technology as well as computers to enable people in different locations to see, hear, and talk with one another

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Workgroup Computing & Groupware

  • Workgroup computing - teams of co-workers use networks of microcomputers to share information and to cooperate on projects

  • Made possible by networks, microcomputers, & groupware

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Telecommuting

  • Telecommuting - working at home while in telecommunication with the office

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Virtual Offices

  • Virtual office - an often nonpermanent and mobile office run with computer and communications technology

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Smart Television

  • Digital television (DTV) - uses a digital signal, or series of 0s and 1s

  • High-definition television (HDTV) - high-resolution type of DTV

  • Standard-definition television (SDTV) - allows broadcasters to transmit more information within the HDTV bandwidth

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Other Practical Uses of Communications

  • Home network - LAN which allows all the personal computers under the same roof to share peripherals and a single modem and Internet service

  • Information/internet appliance - a device merging computing capabilities with communications gadgets

  • TV set-top boxes

  • Internet phones

  • PDAs

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7.3 Communications Channels: The Conduits of Communications

  • Communications channel - the path (physical medium) over which information travels in a telecommunications system from its source to its destination

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The Electromagnetic Spectrum, the Radio Spectrum, & Bandwidth

Radio frequency spectrum

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Wired Communications Channels

  • Twisted-pair wire - two strands of insulated copper wire, twisted around each other

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Wired Communications Channels

  • Coaxial cable - insulated copper wire wrapped in a solid or braided metal shield, then in an external cover

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Wired Communications Channels

  • Fiber-optic cable - dozens or hundreds of thin strands of glass or plastic that transmit pulsating beams of light rather than electricity

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Wireless Communications Channels

  • Infrared transmission - the transmission of data signals using infrared-light waves

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Wireless Communications Channels

Microwave radio - transmits voice & data through the atmosphere as super-high-frequency radio waves called microwaves

  • Broadcast radio - a wireless transmission medium that sends data over long distances--between regions, states, or countries

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Wireless Communications Channels

  • Communications satellites - microwave relay stations in orbit around the earth

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Long-Distance Wireless Communications

  • Global Positioning System (GPS) - a series of earth-orbiting satellites continuously transmitting timed radio signals that can be used to identify earth locations

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Long-Distance Wireless Communications

  • Pagers - simple radio receivers that receive data (but not voice messages) sent from a special radio transmitter

  • One-way pagers

  • Two-way pagers (enhanced paging)

  • Acknowledgments from recipient to sender

  • Email composition & sending

  • Messages to other pagers

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Long-Distance Wireless Communications

Cell - hexagonal shape, usually 8 miles or less in diameter, & served by a transmitter-receiving tower

  • Analog cellular phones - designed primarily for communicating by voice through a system of ground-area cells

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Long-Distance Wireless Communications

  • Digital wireless services (2G) - support digital cellphones & PDAs, using a network of cell towers to send voice communications & data over the airwaves in digital form

  • Broadband wireless digital services (3G) - “always on” technology which can quickly transmit video, still pictures, and music, along with offering better ways to tape into websites than today’s 2G wireless systems

  • 2.5G - compromise between 2G and 3G, which is an “always on” version of 2G technology

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Short-Range Wireless Communications

  • Bluetooth - a short-range wireless digital standard aimed at linking cellphones, PDAs, computers, & peripherals up to distances of 30 feet

  • WiFI - a short-range wireless digital standard aimed at helping machines inside offices to communicate at high speeds and share Internet connections at distances up to 300 feet

  • HomeRF - a separate, incompatible standard designed to network up to 10 PCs & peripherals as far as 150 feet apart

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Compression & Decompression: Putting More Data in Less Space

  • Compression - a method of removing repetitive elements from a file so that the file requires less storage space and therefore less time to transmit

  • Lossless vs. lossy

  • Standards

  • JPEG

  • MPEG

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7.4 Factors Affecting How Data Is Transmitted

  • Transmission rate - a function of two variables:

  • Frequency - the cycles of waves per second

  • Bandwidth - the range between the highest & lowest frequencies

  • Higher frequency => greater transmission rate

  • Larger bandwidth => greater transmission rate

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Factors Affecting How Data Is Transmitted

  • Line configurations

  • Point-to-point line - directly connects the sending & receiving devices

  • Multipoint line - a single line that interconnects several communications devices to one computer

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Factors Affecting How Data Is Transmitted

  • Serial vs. parallel transmission

  • Serial data transmission - bits are transmitted sequentially, one after the other

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Factors Affecting How Data Is Transmitted

Parallel data transmission - bits are transmitted through separate lines simultaneously

  • Serial vs. parallel transmission

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Factors Affecting How Data Is Transmitted

  • Direction of transmission: simplex, half-duplex, & full-duplex

  • Simplex transmission - data can travel in only one direction

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Factors Affecting How Data Is Transmitted

Half-duplex transmission - data travels in both directions but only in one direction at a time

  • Direction of transmission: simplex, half-duplex, & full-duplex

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Factors Affecting How Data Is Transmitted

Full-duplex transmission - data is transmitted back and forth at the same time

  • Direction of transmission: simplex, half-duplex, & full-duplex

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Factors Affecting How Data Is Transmitted

Transmission mode: asynchronous vs. synchronous

  • Asynchronous transmission - data is sent one byte at a time, with each string of bits making up the byte bracketed with special control bits

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Factors Affecting How Data Is Transmitted

Transmission mode: asynchronous vs. synchronous

  • Synchronous transmission - data is sent in blocks, with start and stop bit patterns (synch bytes) at the beginning and end of the blocks

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Factors Affecting How Data Is Transmitted

  • Circuit switching - transmitter has full use of the circuit until all the data has been transmitted and the circuit is terminated

  • Packet switching - electronic messages are divided into packets for transmission over a wide area network to their destination through the most expedient route

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Factors Affecting How Data Is Transmitted

Multiplexing - transmission of multiple signals over a single communications channel

  • Multiplexers

  • Concentrators

  • Front-end processors

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Factors Affecting How Data Is Transmitted

  • Protocol - a set of conventions governing the exchange of data between hardware and/or software components in a communications network

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7.5 Networks

  • Benefits of networks:

  • Sharing of peripheral devices

  • Sharing of programs and data

  • Better communications

  • Security of information

  • Access to databases

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Types of Networks

  • Wide area network (WAN) - a communications network that covers a wide geographical area, such as a country or the world

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Types of Networks

  • Metropolitan area network (MAN) - a communications network covering a city or a suburb

  • Local area network (LAN) - connects computers and devices in a limited geographical area

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Types of Networks

  • Host computer - a mainframe or midsize central computer that controls the network

  • Node - any device that is attached to a network

  • Backbone - a high-speed network that connects LANs and MANs to the Internet

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Types of LANs

  • Client/server LAN:

  • Clients - microcomputers that request data; and

  • Server - a powerful microcomputer that manages shared devices

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Types of LANs

  • Peer-to-peer LAN - all microcomputers on the network communicate directly with one another without relying on a server

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Components of LANs

  • Connection or cabling system

  • Microcomputers with network interface cards

  • Network OS

  • Other shared devices

  • Routers, bridges, and gateways

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Topology of LANs

  • Star network - one in which all microcomputers and other communications devices are connected to a central server

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Topology of LANs

  • Ring network - one in which all microcomputers and other communications devices are connected in a continuous loop

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Topology of LANs

  • Bus network - one in which all communications devices are connected to a common channel

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Intranets, Extranets, & Firewalls

  • Intranet - an organization’s internal private network that uses the infrastructure and standards of the Internet and the WWW

  • Extranets - private intranets that connect not only internal personnel but also selected suppliers and other strategic parties

  • Firewalls - a system of hardware and software that blocks unauthorized users inside and outside the organization from entering the intranet

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7.6 The Future of Communications

  • Satellite-based systems

  • Beyond 3G to 4G

  • Photonics: optical technologies at warp speed

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7.7 Cyberethics

  • Controversial material & censorship:

  • Blocking software

  • Browsers with ratings

  • The V-Chip

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Cyberethics

  • Privacy - the right of people not to reveal information about themselves

  • Cookie - a file that the web server stores on your hard-disk drive when you visit a website

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Concept Check

  • What kind of signal varies continuously in strength and/or quality?

  • Analog signal

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Concept Check

  • What is a general term for very high-speed connections?

  • Broadband

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Concept Check

  • What type of cable consists of insulated copper wire wrapped in a solid or braided metal shield, then in an external cover?

  • Coaxial (co-ax) cable

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Concept Check

  • What are the three zones in space which satellite systems may occupy?

  • GEO, MEO, and LEO

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Concept Check

  • What system consists of a series of earth-orbiting satellites continuously transmitting timed radio signals that can be used to identify earth locations?

  • Global Positioning System (GPS)

Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.


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Concept Check

  • Which modem modulates digital signals into analog signals for transmission over phone lines--a sending or receiving modem?

  • Sending modem

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Concept check58 l.jpg

Concept Check

  • What is the term for working at home while in telecommunication with the office?

  • Telecommuting

Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.


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Concept Check

  • What is the term for an often nonpermanent and mobile office run with computer and communications technology?

  • Virtual office

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Concept Check

  • What type of compression loses a certain amount of accuracy in exchange for a high degree of compression?

  • Lossy compression

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Concept Check

  • What is the leading compression standard for still images?

  • JPEG

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Concept Check

  • What type of transmission involves data traveling in both directions but only in one direction at a time?

  • Half-duplex

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Concept Check

  • What is the term for the transmission of multiple signals over a single communications channel?

  • Multiplexing

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Concept check64 l.jpg

Concept Check

  • What is the term for a set of conventions governing the exchange of data between hardware and/or software components in a communications network?

  • Protocol

Copyright © 2003. Exclusive rights by The McGraw-Hill Companies, Inc.


Concept check65 l.jpg

Concept Check

  • Which type of LAN involves all microcomputers on the network communicating directly with one another without relying on a server?

  • Peer-to-peer LAN

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Concept Check

  • Which LAN topology connects all microcomputers and other communications devices in a continuous loop?

  • Ring network

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Concept check67 l.jpg

Concept Check

  • What is an organization’s internal private network that uses the infrastructure and standards of the Internet and the WWW called?

  • Intranet

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Concept Check

  • What are Bluetooth, WiFi, and HomeRF examples of?

  • Short-range wireless communications

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Concept Check

  • What is the term for teams of co-workers using networks of microcomputers to share information and to cooperate on projects?

  • Workgroup computing (collaborative computing)

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Concept Check

  • What type of data transmission transmits bits sequentially, one after the other?

  • Serial data transmission

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Concept check71 l.jpg

Concept Check

  • What is a system of hardware and software that blocks unauthorized users inside and outside the organization from entering the intranet?

  • Firewall

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