Using Information Technology Telecommunications

2 The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable.

Telecommunications 3 WHAT IS A NETWORK? A network is simply two or more computers that are linked together. The most common types of networks are: Local Area Networks (LANS) Metropolitan Area Networks (MANS) Wide Area Networks (WANS).

Telecommunications 4 Types of Networks Metropolitan area network (MAN) - a communications network covering a city or a suburbMAN Local area network (LAN) - connects computers and devices in a limited geographical area

Telecommunications 5 Types of Networks Wide area network (WAN) - a communications network that covers a wide geographical area, such as a country or the world

Telecommunications 6 BENEFITS OF A NETWORKS Information sharing: Authorized users can use other computers on the network to access and share information and data. This could include special group projects, databases, etc. Hardware sharing: One device connected to a network, such as a printer or scanner, can be shared by many users.

Telecommunications 7 BENEFITS OF A NETWORKS Software sharing: Instead of purchasing and installing a software program on each computer, it can be installed on the server. All of the users can then access the program from a single location. Collaborative environment: Users can work together on group projects by combining the power and capabilities of diverse equipment.

Telecommunications 8 COMMUNICATIONS MEDIA Communications Channel To transfer data from one computer to another requires some type of link through which the data can be transmitted. This link is known as the communications channel. To send data through the channel requires some type of transmission media, which may be either physical or wireless.

Telecommunications 9 Wired Communications Channels Twisted-pair -cable - consists of two independently insulated wires twisted around each other (least expensive type of cable—the kind that is used in many telephone systems)

Telecommunications 10 Wired Communications Channels Coaxial cable - insulated copper wire wrapped in a solid or braided metal shield, then in an external cover (the primary type of cabling used by the cable television industry; it is more expensive than twisted pair)

Telecommunications 11 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

Telecommunications 12 Characteristics Of Cables Twisted-pair wire characteristics: Slow. Does not protect well against electrical interference. Prevalent! Used extensively in telephone lines. Coaxial cable characteristics: Better than twisted- pair wiring at resisting noise. Carries voice & data at faster rate than twisted-pair. Widely used in cable television.

Telecommunications 13 Characteristics Of Cables Fiber-optic cable characteristics: Unaffected by random electromagnetic interference Lighter and more durable than twisted-pair & co-ax cable

Telecommunications 14 Wireless Communications Channels Infrared transmission - the transmission of data signals using infrared-light waves

Telecommunications 15 Wireless Communications Channels Broadcast radio - a wireless transmission medium that sends data over long distances-- between regions, states, or countries Microwave radio - transmits voice & data through the atmosphere as super-high-frequency radio waves called microwaves

Telecommunications 16 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

Telecommunications 17 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

Telecommunications 18 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

Telecommunications 19 Factors Affecting How Data Is Transmitted Serial vs. parallel transmission Serial data transmission - bits are transmitted sequentially, one after the other

Telecommunications 20 Factors Affecting How Data Is Transmitted Serial vs. parallel transmission Parallel data transmission - bits are transmitted through separate lines simultaneously

Telecommunications 21 Factors Affecting How Data Is Transmitted Direction of transmission: simplex, half-duplex, & full-duplex Simplex transmission - data can travel in only one direction

Telecommunications 22 Factors Affecting How Data Is Transmitted Direction of transmission: simplex, half-duplex, & full-duplex Half-duplex transmission - data travels in both directions but only in one direction at a time

Telecommunications 23 Factors Affecting How Data Is Transmitted Direction of transmission: simplex, half-duplex, & full-duplex Full-duplex transmission - data is transmitted back and forth at the same time

Telecommunications 24 Factors Affecting How Data Is Transmitted Asynchronous transmission - data is sent one byte at a time, with each string of bits making up the byte bracketed with special control bits Transmission mode: asynchronous vs. synchronous

Telecommunications 25 Factors Affecting How Data Is Transmitted Synchronous transmission - data is sent in blocks, with start and stop bit patterns (synch bytes) at the beginning and end of the blocks Transmission mode: asynchronous vs. synchronous

Telecommunications 26 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

Telecommunications 27 Factors Affecting How Data Is Transmitted Multiplexers: a device that merges several low-speed transmissions into one high-speed transmission. Concentrators: collects data in a temporary storage area. Front-end processors: a smaller computer that is connected to a larger computer and assists with communications functions.

Telecommunications 28 HOW ARE NETWORKS CATEGORIZED? Networks are usually classified using three properties: Topology Protocol Architecture

Telecommunications 29 Topology of LANs Bus network - one in which all communications devices are connected to a common channel

Telecommunications 30 Topology of LANs Ring network - one in which all microcomputers and other communications devices are connected in a continuous loop

Telecommunications 31 Topology of LANs Star network - one in which all microcomputers and other communications devices are connected to a central server

Telecommunications 32 NETWORK/COMMUNICATION PROTOCOLS Protocol - a set of conventions governing the exchange of data between hardware and/or software components in a communications network

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Telecommunications 35 Types of LANS Peer-to-peer LAN - all microcomputers on the network communicate directly with one another without relying on a server

Telecommunications 36 Types of LANS Client/server LAN: Clients - microcomputers that request data; and Server - a powerful microcomputer that manages shared devices

Telecommunications 37 NETWORKING HARDWARE AND SOFTWARE Hub – electronic device (with a number of ports) used in a LAN to link groups of computers Repeaters (also called amplifiers) – electronic devices that receive signals and amplify and send them along the network Routers - electronic devices used to ensure messages are sent to their intended destinations

Telecommunications 38 NETWORKING HARDWARE AND SOFTWARE Gateway – consists of hardware and/or software that allows communications between dissimilar networks Bridge – consists of hardware and/or software that allows communication between two similar networks

Telecommunications 39 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