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8/14/2019 Effective Communications Are Essential to Organizational
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Principles of Information Systems, Seventh Edition 2
Effective communications are essential to organizational
success
Define the terms communications and telecommunicationsand describe the components of a telecommunications
system
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Principles of Information Systems, Seventh Edition 3
An unmistakable trend of communications technology isthat more people are able to send and receive all forms ofinformation over greater distances at a faster rate
Identify broad categories of communications media anddiscuss the basic characteristics of specific media types
Describe how a modem works
Explain the types of telecommunications carriers today and theservices they provide
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Principles of Information Systems, Seventh Edition 4
Identify the benefits associated with a telecommunications
network
Define the term network topology and identify five
alternatives Discuss the different communications protocols and
devices used for telecommunications
Name three distributed processing alternatives and discuss
their basic features List some telecommunications applications that
organizations are benefiting from today
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Principles of Information Systems, Seventh Edition 5
An Overview Of Communications
Systems
Communications: the transmission of a signal by way of
a medium from a sender to a receiver
Signal contains a message composed of data and
information
In telecommunications, sender transmits a signal through
a transmission medium such as a cable
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An Overview Of Communications
Systems (continued)
Communications can be synchronous or asynchronous
Synchronous communications: the receiver gets the
message instantaneously
Asynchronous communications: the receiver gets the
message some period of time after it is sent
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Telecommunications
Telecommunications: electronic transmission of signals
for communications, via telephone, radio, television, etc.
Data communications: subset of telecommunications that
refers to the electronic collection, processing, anddistribution of data, typically between computer system
hardware devices
Telecommunications medium: anything that carries an
electronic signal and interfaces between a sending device
and a receiving device
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Figure 6.3: Elements of a
Telecommunications System
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Communications Channels: Basic
Communications Channel
Characteristics
Communication channels can be classified as simplex,
half-duplex, or full-duplex
Simplex channel: can transmit data in only one direction
Half-duplex channel: can transmit data in either direction,
but not simultaneously
Full-duplex channel: permits data transmission in both
directions at the same time
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Channel Bandwidth and Information-
Carrying Capacity
Bandwidth: the range of frequencies that an electronic
signal occupies on a given transmission medium
Shannons fundamental law of information theory:
states that the information-carrying capacity of a channel
is directly proportional to its bandwidth
Broadband: telecommunications in which a wide bandof frequencies is available to transmit information
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Types of Media
Guided transmission media: communications signals are
guided along a solid medium
Wireless media: communications signals are sent overairwaves
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Table 6.1: Transmission Media Types
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Table 6.1: Transmission Media Types
(continued)
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Modems
A typical telephone line can only accommodate an analog
signal (a continuous, curving signal)
A computer generates a digital signal representing bits
Modem: a device that translates data from digital to
analog and analog to digital
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Figure 6.8: How a Modem Works
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Multiplexers
Multiplexers: devices that allow several
telecommunications signals to be transmitted over a
single communications medium at the same time
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Figure 6.9: Use of a Multiplexer to
Consolidate Data Communications onto
a Single Communications Link
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Front-End Processors
Front-end processors: special-purpose computers that
manage communications to and from a computer system
Connect a midrange or mainframe computer to hundredsor thousands of communications lines
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Figure 6.10: Front-End Processor
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Carriers and Services
Local exchange carrier (LEC): a public telephone
company in the United States that provides service to
homes and businesses within its defined geographical area
Competitive local exchange carrier (CLEC): a company
that is allowed to compete with the LECs, such as a
wireless, satellite, or cable service provider
Long-distance carrier: a traditional long-distance phone
provider, such as AT&T, Sprint, or MCI
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Principles of Information Systems, Seventh Edition 22
Switched and Dedicated Lines
Switched line: a communications line that uses switching
equipment to allow one transmission device to be
connected to other transmission devices
Dedicated line: a communications line that provides a
constant connection between two points; also called a
leased line
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Principles of Information Systems, Seventh Edition 23
Voice and Data Convergence
Voice over Internet protocol (VoIP): the basic transport
of voice in the form of a data packet using the Internet
protocol
IP telephonyis the technology for transmitting voice
communications over a network using an open standards-
based Internet protocol
Voice and data convergence: the integration of voice
and data applications in a common environment
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Principles of Information Systems, Seventh Edition 24
WATS
Wide-area telephone service (WATS): a fixed-rate
long-distance telecommunications service for heavy users
of voice services
IN-WATS service
OUT-WATS service
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Principles of Information Systems, Seventh Edition 25
ISDN
Integrated services digital network (ISDN): a set of
standards for integrating voice and data communications
onto a single line via digital transmission over copper
wire or other media
ISDN requires special adapters at both ends of the
transmission line
ISDN Basic Rate Interface
ISDN Primary Rate Interface
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Principles of Information Systems, Seventh Edition 26
Figure 6.12: ISDN Network Switching
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Principles of Information Systems, Seventh Edition 27
T-Carrier System
Introduced in the 1960s to support digitized voice
transmission
Uses four wires and provides duplex capability
T-1 carrier is capable of carrying 1.544 Mbps over copperwire; commonly used in U.S., Japan, and Canada
T-3 line is capable of transmitting data at a rate of
44.736 Mbps
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Principles of Information Systems, Seventh Edition 28
Digital Subscriber Line (DSL)
Digital subscriber line (DSL): a telecommunications
technology that delivers high-bandwidth information to
homes and small businesses over ordinary copper
telephone wires
Provides a transmission rate of 512 Kbps to 1.544 Mbps
from the central office to the subscriber
Provides a transmission rate of about 128 Kbps from thesubscriber to the central office
Can carry both data and voice signals
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Principles of Information Systems, Seventh Edition 29
Wireless Mobile
Table 6.3: Some Wireless Data Communications Options
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Principles of Information Systems, Seventh Edition 30
Networks
Computer network: the communications media, devices,
and software needed to connect two or more computer
systems and/or devices
Network nodes: the computers and devices on the
networks
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Principles of Information Systems, Seventh Edition 31
Network Types
Personal area network (PAN)
Local area network (LAN)
Metropolitan area network (MAN)
Wide area network (WAN)
International network
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Principles of Information Systems, Seventh Edition 32
Network Topology
Network topology: logical model that describes how
networks are structured or configured
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Principles of Information Systems, Seventh Edition 33
Figure 6.15: The Basic Network
Topologies
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Principles of Information Systems, Seventh Edition 34
Terminal-to-Host, File Server, and
Client/Server Systems
Classifications based on how computers on the network
connect and interoperate
Terminal-to-host: application and database reside on one
host computer, and the user interacts with application anddata using a dumb terminal
File server: the application and database reside on one host
computer (file server)
Client/server: multiple computer platforms are dedicatedto special functions such as database management, printing,
communications, and program execution
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Principles of Information Systems, Seventh Edition 35
Figure 6.18: Client/Server Connection
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Principles of Information Systems, Seventh Edition 36
Interconnecting Networks:
Communications Protocols
Open Systems Interconnection (OSI) model
Transmission Control Protocol/Internet Protocol (TCP/IP)
Systems Network Architecture (SNA)
IEEE 802.3 (Ethernet)
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Principles of Information Systems, Seventh Edition 37
Communications Protocols (continued)
Frame Relay
Asynchronous Transfer Mode (ATM)
FireWire
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Principles of Information Systems, Seventh Edition 38
Wireless Communications Protocols
Bluetooth
IEEE 802.11b (Wi-Fi)
IEEE 802.11g
IEEE 802.16 (WiMax)
IEEE 802.20 (MBWA)
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Principles of Information Systems, Seventh Edition 39
Wireless Communications Protocols
(continued)
1G
2G
2.5G
3G
Multichannel Multipoint Distribution System (MMDS)
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Principles of Information Systems, Seventh Edition 41
Network Switching Devices (continued)
Router: a device or software in a computer that
determines the next network point to which a data packet
should be forwarded toward its destination
Hub: a place of convergence where data arrives from one
or more directions and is forwarded out in one or more
other directions
Gateway: a network point that acts as an entrance to
another network
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Principles of Information Systems, Seventh Edition 42
Network Basics: Basic Processing
Strategies
Centralized processing: all processing occurs in a single
location or facility
Decentralized processing: processing devices are placedat various remote locations
Distributed processing: computers are placed at remote
locations but connected to each other via a network
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Principles of Information Systems, Seventh Edition 43
Communications Software
Network operating system (NOS): systems software
that controls the computer systems and devices on a
network and allows them to communicate with each other
Network-management software: enables a manager on
a networked desktop to monitor the use of individual
computers and shared hardware, scan for viruses, and
ensure compliance with software licenses
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Principles of Information Systems, Seventh Edition 44
Telecommunications Applications
Linking personal computers to mainframes and networks
Voice mail
Electronic software distribution
Electronic document distribution
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Principles of Information Systems, Seventh Edition 45
Telecommunications Applications
(continued)
Call centers
Telecommuting
Videoconferencing
Electronic data interchange (EDI)
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Principles of Information Systems, Seventh Edition 46
Telecommunications Applications
(continued)
Public network services
Electronic funds transfer (EFT)
Distance learning
Specialized systems and services
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Principles of Information Systems, Seventh Edition 47
Summary
Communications: the transmission of a signal by way of
a medium from a sender to a receiver
In telecommunications, the sender transmits a signal
through a transmission medium such as a cable Transmission media types: twisted-pair wire cable,
coaxial cable, fiber-optic cable, microwave, cellular, and
infrared
Telecommunications carriers can be divided into localexchange carriers, competitive local exchange carriers,
and long-distance carriers
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Principles of Information Systems, Seventh Edition 48
Summary (continued)
A computer network consists of the communications
media, devices, and software needed to connect two or
more computer systems and/or devices
Network types: personal area network (PAN), local areanetwork (LAN), metropolitan area network (MAN), wide
area network (WAN), and international network
Network topologies: ring, bus, hierarchical, star, and
hybrid
Options for how computers on a network connect:
terminal-to-host, file server, and client/server
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Summary (continued)
Communications protocols include the Open Systems
Interconnection (OSI) model, Transmission Control
Protocol/Internet Protocol (TCP/IP), IEEE 802.3
(Ethernet), etc.
Network switching devices: private branch exchange
(PBX), bridge, switch, router, hub, and gateway
Examples of telecommunications applications are voice
mail, electronic software distribution, telecommuting,
videoconferencing, electronic funds transfer, and distance
learning