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Slide Presentasi Chapter 6 Principles of Information Systems
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Principles of Information Systems, Seventh Edition 2
• Effective communications are essential to organizational success
• Define the terms communications and telecommunications and describe the components of a telecommunications system
Principles of Information Systems, Seventh Edition 3
• An unmistakable trend of communications technology is that more people are able to send and receive all forms of information over greater distances at a faster rate
• Identify broad categories of communications media and discuss the basic characteristics of specific media types
• Describe how a modem works• Explain the types of telecommunications carriers today and the
services they provide
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
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
Principles of Information Systems, Seventh Edition 6
Figure 6.2: Communications and Telecommunications
Principles 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
Principles of Information Systems, Seventh Edition 8
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, and distribution 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
Principles of Information Systems, Seventh Edition 9
Figure 6.3: Elements of a Telecommunications System
Principles of Information Systems, Seventh Edition 10
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
Principles of Information Systems, Seventh Edition 11
Channel Bandwidth and Information-Carrying Capacity
• Bandwidth: the range of frequencies that an electronic signal occupies on a given transmission medium
• Shannon’s 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 band of frequencies is available to transmit information
Principles of Information Systems, Seventh Edition 12
Types of Media
• Guided transmission media: communications signals are guided along a solid medium
• Wireless media: communications signals are sent over airwaves
Principles of Information Systems, Seventh Edition 13
Table 6.1: Transmission Media Types
Principles of Information Systems, Seventh Edition 14
Table 6.1: Transmission Media Types (continued)
Principles of Information Systems, Seventh Edition 15
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
Principles of Information Systems, Seventh Edition 16
Figure 6.8: How a Modem Works
Principles of Information Systems, Seventh Edition 17
Multiplexers
• Multiplexers: devices that allow several telecommunications signals to be transmitted over a single communications medium at the same time
Principles of Information Systems, Seventh Edition 18
Figure 6.9: Use of a Multiplexer to Consolidate Data Communications onto
a Single Communications Link
Principles of Information Systems, Seventh Edition 19
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 hundreds or thousands of communications lines
Principles of Information Systems, Seventh Edition 20
Figure 6.10: Front-End Processor
Principles of Information Systems, Seventh Edition 21
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
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
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 telephony is 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
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
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
Principles of Information Systems, Seventh Edition 26
Figure 6.12: ISDN Network Switching
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 copper wire; commonly used in U.S., Japan, and Canada
• T-3 line is capable of transmitting data at a rate of 44.736 Mbps
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 the subscriber to the central office
• Can carry both data and voice signals
Principles of Information Systems, Seventh Edition 29
Wireless Mobile
Table 6.3: Some Wireless Data Communications Options
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
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
Principles of Information Systems, Seventh Edition 32
Network Topology
• Network topology: logical model that describes how networks are structured or configured
Principles of Information Systems, Seventh Edition 33
Figure 6.15: The Basic Network Topologies
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 and data using a “dumb” terminal
• File server: the application and database reside on one host computer (file server)
• Client/server: multiple computer platforms are dedicated to special functions such as database management, printing, communications, and program execution
Principles of Information Systems, Seventh Edition 35
Figure 6.18: Client/Server Connection
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)
Principles of Information Systems, Seventh Edition 37
Communications Protocols (continued)
• Frame Relay
• Asynchronous Transfer Mode (ATM)
• FireWire
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)
Principles of Information Systems, Seventh Edition 39
Wireless Communications Protocols (continued)
• 1G
• 2G
• 2.5G
• 3G
• Multichannel Multipoint Distribution System (MMDS)
Principles of Information Systems, Seventh Edition 40
Network Switching Devices
• Private branch exchange (PBX): an on-premise switching system owned or leased by a private enterprise that interconnects its telephones and provides access to the public telephone system
• Bridge: a device used to connect two or more networks that use the same communications protocol
• Switch: a telecommunications device that routes incoming data from any one of many ports to a specific output port that will take the data toward its intended destination
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
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 placed at various remote locations
• Distributed processing: computers are placed at remote locations but connected to each other via a network
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
Principles of Information Systems, Seventh Edition 44
Telecommunications Applications
• Linking personal computers to mainframes and networks
• Voice mail
• Electronic software distribution
• Electronic document distribution
Principles of Information Systems, Seventh Edition 45
Telecommunications Applications (continued)
• Call centers
• Telecommuting
• Videoconferencing
• Electronic data interchange (EDI)
Principles of Information Systems, Seventh Edition 46
Telecommunications Applications (continued)
• Public network services
• Electronic funds transfer (EFT)
• Distance learning
• Specialized systems and services
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 local exchange carriers, competitive local exchange carriers, and long-distance carriers
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 area network (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
Principles of Information Systems, Seventh Edition 49
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
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