• effective communications are essential to organizational

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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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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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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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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7/49Principles of Information Systems, Seventh Edition 7

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



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



Figure 6.3: Elements of a

Telecommunications System



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



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



Types of Media

Guided transmission media: communications signals are

guided along a solid medium

Wireless media: communications signals are sent overairwaves



Table 6.1: Transmission Media Types



Table 6.1: Transmission Media Types

(continued)



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



Figure 6.8: How a Modem Works



Multiplexers

Multiplexers: devices that allow several

telecommunications signals to be transmitted over a

single communications medium at the same time



Figure 6.9: Use of a Multiplexer to

Consolidate Data Communications onto

a Single Communications Link



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



Figure 6.10: Front-End Processor



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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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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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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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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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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Figure 6.12: ISDN Network Switching


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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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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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Wireless Mobile

Table 6.3: Some Wireless Data Communications Options


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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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Network Types

Personal area network (PAN)

Local area network (LAN)

Metropolitan area network (MAN)

Wide area network (WAN)

International network


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Network Topology

Network topology: logical model that describes how

networks are structured or configured


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Figure 6.15: The Basic Network

Topologies


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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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Figure 6.18: Client/Server Connection


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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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Communications Protocols (continued)

Frame Relay

Asynchronous Transfer Mode (ATM)

FireWire


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Wireless Communications Protocols

Bluetooth

IEEE 802.11b (Wi-Fi)

IEEE 802.11g

IEEE 802.16 (WiMax)

IEEE 802.20 (MBWA)


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Wireless Communications Protocols

(continued)

1G

2G

2.5G

3G

Multichannel Multipoint Distribution System (MMDS)


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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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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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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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Telecommunications Applications

Linking personal computers to mainframes and networks

Voice mail

Electronic software distribution

Electronic document distribution


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(continued)

Call centers

Telecommuting

Videoconferencing

Electronic data interchange (EDI)


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(continued)

Public network services

Electronic funds transfer (EFT)

Distance learning

Specialized systems and services


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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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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

• effective communications are essential to organizational

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