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Information Technology
Telecommunications and Networks
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Learning Objectives
When you finish this chapter, you will: Recognize why successful managers must be
familiar with telecommunications concepts and terminology.
Know the principles of communication within a computer system and among computers.
Be able to identify the major media and devices that are used in telecommunications.
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Learning Objectives
Be able to list and explain the functions of different network layouts and the concept of protocols.
Understand how telecommunications can improve operations in organizations.
Know the latest developments in telecommunications media and transmission speeds.
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Telecommunications in Business Telecommunications
Transmittal of data from one computer to another over a distance
Telecommunications has improved business in three main ways: Better communication Higher efficiency Better distribution of data
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What is Data Communications?
Data Communications Any transfer of data within a computer,
between a computer and another device, or between two computers
Two Basic Modes Parallel transmission Serial transmission
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Communication Direction
Three Modes of Communication Between Devices Simplex
One-way in one direction Half-Duplex
One-way in two directions Full-Duplex
Two-way in two directions
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Communication Direction
Figure 6.2 Simplex, half-duplex, and full-duplex communication
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Communication Direction
Asynchronous Communication In asynchronous transmission, the devices are not
synchronized by any timing aids. Advantage of asynchronous transmission
Does not need sophisticated and expensive timing hardware
Disadvantage of asynchronous transmission Overhead, time spent transmitting bits that are not a part
of the primary data
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Communication Modes
Synchronous Communication In synchronous communication, data are
transmitted using timing devices. Messages are transmitted in packets. Advantage of synchronous communication
Overhead in synchronous communication is significantly smaller than in asynchronous communication.
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Communication Modes
Figure 6.4 Synchronous transmission
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Channels and Media
Communication Channel Physical medium through which data can
be communicated. Channel Capacity
Narrow band Broadband
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Channels and Media
Figure 6.5 Transmission speed measurement unit
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Channels and Media
Media A medium is any means by which data can be
transmitted. Transmission speed
A medium’s capacity is determined by the range of bits per second at which it can operate.
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Channels and Media
Figure 6.6 Telecommunications transmission speeds of different media
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Channels and Media
Twisted Pair Telephone line made of a pair of copper wires twisted to
reduce electromagnetic interference (EMI) Coaxial Cable
Commonly used for cable television transmission More expensive than twisted pair Greater transmission rate than twisted pair Much less susceptible to EMI
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Channels and Media
Microwaves High-frequency, short radio-frequency (RF) waves
Terrestrial microwave Satellite microwave
Optical Fiber Fiber-optic technology uses light instead of
electricity to transmit data.
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Channels and Media
Figure 6.7 Characteristics of channel media
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Analog vs. Digital
Analog signals A continuous series of waves
Digital signals A series of discrete bits
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Modulation
Modification of a digital signal into an analog signal
Demodulation Modification of an analog signal into a
digital signal
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Modulation
Figure 6.8 Signal modulation
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Modulation
Amplitude Modulation (AM)
Frequency Modulation (FM)
Phase Modulation
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Modulation
Modems Devices that modulate and demodulate
signals Multiplexers
Devices that allow several telephones or computers to transmit data through a single line Frequency division multiplexing Time-division multiplexing
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Modulation
Figure 6.9 Multiplexing
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Modulation
Figure 6.10 Frequency division
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Networks
LANs (Local Area Networks) Networks within a building, or within a group of
adjacent buildings WANs (Wide Area Networks)
Networks that cross organizational boundaries or reach outside the company Value-added networks (VANs) Wireless communication
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Networks
Figure 6.11 Where wireless LANs are a good choice
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Networks
Network Topology Physical layout of the nodes in a network
Star Ring Bus Tree
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Network Topology
Figure 6.12 Network topologies
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Protocols
Communication protocols Rules governing the communication between
computers or between computers and other computer-related devices
Network protocols Rules governing a network of devices
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Protocols
Figure 6.13 Some communications software allows a user to establish protocols: bit rate, parity, number of data bits, stop bits, and a
handshake procedure.
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Protocols
LAN Protocols Polling Contention Token passing
WAN Protocols OSI (Open Systems Interconnection)
Standard protocol model Seven layers
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Protocols
Figure 6.14 The seven layers of the OSI model
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Switching Techniques and Transfer Modes Circuit Switching Message is communicated in its entirety from the
transmitting computer to the receiving computer Packet Switching
Message is divided into packets of bytes and transmitted via several nodes
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The Changing Business Environment
Cellular Phones Teleconferencing Voice Mail Facsimile
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Ethical and Societal IssuesTelecommuting: Pros and Cons Pros
Saves travel cost and time Decreases pollution May reduce unemployment. Productivity higher among telecommuters
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Ethical and Societal IssuesTelecommuting: Pros and Cons Cons
Employers tend to pressure telecommuters to work harder than workers in the office.
No office to foster new social ties and camaraderie.
May negatively impact some segments of the economy Restaurants Downtown business and industries