Chapter 9 Communications And Networks


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Chapter 9 Communications And Networks

  1. 1. Chapter 9 Communications and Networks
  2. 2. Chapter 9 Objectives Define the components required for successful communications Identify various sending and receiving devices Explain communications applications List advantages of using a network Differentiate between a local area network and a wide area network Understand the various communications technologies Identify uses of intranets and extranets Explain the purpose of communications software Understand the telephone network Describe commonly used communications devices Identify various physical and wireless transmission media p.9.2 Next
  3. 3. Communications <ul><li>What is computer communications? </li></ul><ul><li>A process in which one computer transfers data, instructions, and information to another computer(s) </li></ul>p.9.2 Fig. 9-1 Next <ul><li>A communications system contains all types of devices </li></ul><ul><li>personal computers </li></ul><ul><li>notebook computers </li></ul><ul><li>Web-enabled cellular telephones </li></ul><ul><li>Web-enabled handheld computers </li></ul><ul><li>WebTV ™ </li></ul><ul><li>GPS receivers </li></ul>a a d c b e a a f c
  4. 4. Communications <ul><li>What is needed for successful communications? </li></ul>p.9.2 Next sending device Initiates an instruction to transmit data, instructions, or information communications device Converts or formats the data, instructions, or information from the sending device into signals carried by a communications channel communications channel A path on which the signals travel communications device Receives the signals from the communications channel and converts or formats them so the receiving device can understand the signals receiving device Accepts the data, instructions, or information
  5. 5. Communications <ul><li>What is the primary function of a communications device? </li></ul><ul><li>To convert or format signals so they are suitable for the communications channel or a receiving device </li></ul>p.9.3 Fig. 9-2 Next analog signal A continuous electrical wave digital signal Individual electrical pulses that represent the bits grouped together into bytes
  6. 6. Sending and Receiving Devices <ul><li>What is a sending and receiving device? </li></ul><ul><li>Initiates or accepts transmission of data, instructions, and information </li></ul>p.9.3 mainframe computers mid-range servers desktop computers notebook computers Next Internet appliances and Web-enabled devices
  7. 7. Sending and Receiving Devices <ul><li>What are some specialized sending and receiving devices? </li></ul>p.9.3 Fig. 9-3 Next Internet appliance Also called a Web appliance Computer with limited functionality whose main purpose is to connect to the Internet from home Web-enabled device Handheld device that provides access to the Internet and e-mail from any location Internet appliance Web-enabled cellular telephone Web-enabled handheld computer set-top box
  8. 8. Uses of Communications Technologies <ul><li>What are some uses of communications technology? </li></ul><ul><li>Communications technology use is all around you </li></ul>p.9.4 Next voice mail fax e-mail instant messaging chat rooms newsgroups telephony videoconferencing collaboration groupware global positioning system (GPS)
  9. 9. Uses of Communications Technologies <ul><li>What is voice mail? </li></ul><ul><li>Allows callers to leave a voice message for the called party </li></ul><ul><li>Unlike answering machines, voice mail converts an analog voice message into digital form </li></ul><ul><li>The message is stored in a voice mailbox </li></ul><ul><li>A voice mailbox is a storage location on a computer in the voice mail system </li></ul>p.9.4 Next
  10. 10. Uses of Communications Technologies <ul><li>What is fax? </li></ul><ul><li>A document transmitted and received over telephone lines </li></ul><ul><li>Can contain handwritten or typed text, illustrations, photographs, or other graphics </li></ul><ul><li>You can send or receive a fax using a stand-alone fax machine or a computer fax modem </li></ul>p.9.5 Next
  11. 11. Uses of Communications Technologies <ul><li>What is e-mail (electronic mail)? </li></ul><ul><li>The exchange of text messages and computer files transmitted via a communications network </li></ul><ul><li>To send and receive e-mail messages, you use e-mail software installed on your computer </li></ul>p.9.5 Next
  12. 12. Uses of Communications Technologies <ul><li>What is instant messaging (IM)? </li></ul><ul><li>A real-time Internet communications service that notifies you when one or more people are online and then allows you to exchange messages or files with them or join a private chat room </li></ul>Step 4: Your instant message travels through a messaging server and then to the online buddy. Step 2: Server checks if any of your established friends, family, or co-workers, called buddies, are online. Step 3: You send instant messages to an online buddy. p.9.6 Fig. 9-4 Step 1 Step 2 IM server Step 1 Step 2 Step 3 IM server Next Step 1 Step 2 Step 4 Step 3 IM server messaging server Step 1: Login to the IM server. Step 1 IM server
  13. 13. Uses of Communications Technologies <ul><li>What is a chat room? </li></ul><ul><li>Permits users to converse in real time with each other via the computer while connected to the Internet </li></ul><ul><li>Types of chat rooms </li></ul><ul><ul><li>Voice chats </li></ul></ul><ul><ul><li>Video chats </li></ul></ul><ul><ul><li>Radio chats </li></ul></ul>p.9.6 Fig. 9-5 Next
  14. 14. Uses of Communications Technologies <ul><li>What is a newsgroup? </li></ul><ul><li>An area on the Web where users conduct written discussions about a particular subject </li></ul><ul><li>Also called a threaded discussion </li></ul><ul><li>The difference between a chat room and a newsgroup is that a chat room is a live conversation, and the newsgroup is not </li></ul>p.9.7 Next synchronous real-time live communications asynchronous communications that are not real time
  15. 15. Uses of Communications Technologies <ul><li>What is Internet telephony? </li></ul><ul><li>Enables you to talk to other people over the Internet </li></ul><ul><li>Uses the Internet to connect a calling party and one or more called parties </li></ul><ul><li>You need Internet telephone software </li></ul><ul><li>Speak into a a computer microphone </li></ul><ul><li>Internet telephone software and your computer’s sound card digitize and compress your conversation and then transmit the digitized audio </li></ul>p.9.8 Next
  16. 16. Uses of Communications Technologies <ul><li>What is videoconferencing? </li></ul><ul><li>Involves using video and computer technology to conduct a meeting between participants at two or more geographically separate locations </li></ul><ul><li>Requires computers with microphones, speakers, video cameras, and communications devices and software </li></ul>p.9.8 Fig. 9-6 Next
  17. 17. Uses of Communications Technologies <ul><li>What are other conferencing systems? </li></ul><ul><li>Web conference </li></ul><ul><ul><li>Conferencing system that uses the Internet, Web browsers, and Web servers to deliver this service </li></ul></ul><ul><li>Video telephone call </li></ul><ul><ul><li>Used by home users to see each other as they talk on the Internet </li></ul></ul>p.9.8 Fig. 9-6 Next
  18. 18. <ul><li>Working with other users connected to a server </li></ul><ul><li>You can conduct online meetings </li></ul><ul><ul><li>Allows you to share documents with others in real time </li></ul></ul><ul><li>You also can collaborate via e-mail </li></ul><ul><li>Microsoft’s NetMeeting allows collaboration </li></ul>Uses of Communications Technologies <ul><li>What is collaboration? </li></ul>p.9.9 Fig. 9-7 Start Net Meeting command Next NetMeeting window Word document chat room
  19. 19. Uses of Communications Technologies <ul><li>What is groupware? </li></ul><ul><li>A software application that helps groups of people work together on projects and share information over a network </li></ul><ul><li>A component of workgroup computing </li></ul><ul><ul><li>includes network hardware and software that enables group members to work together </li></ul></ul><ul><li>Most groupware provides personal information manager (PIM) functions </li></ul>p.9.10 Next manage projects communicate make group decisions schedule meetings
  20. 20. Uses of Communications Technologies <ul><li>What is a global positioning system (GPS)? </li></ul><ul><li>Consists of one or more earth-based receivers that accept and analyze signals sent by satellites in order to determine the receiver’s geographic location </li></ul>p.9.10 Fig. 9-8 “ Where am I?” Step 1: GPS satellites orbit the earth. Every thousandth of a second, each satellite sends a signal that indicates its current position to the GPS receiver. Step 1 Next Step 2: A GPS receiver (such as in a car) determines its location on Earth by analyzing signals from the satellites. Step 2
  21. 21. Uses of Communications Technologies <ul><li>What is Digital Angel ™? </li></ul><ul><li>A computer chip containing a GPS device </li></ul><ul><li>Worn as a bracelet or woven into fabric that has an antenna that communicates with the GPS satellite </li></ul><ul><li>Measures and sends biological information to the satellite </li></ul>p.9.10 Next
  22. 22. Networks <ul><li>What is a network? </li></ul><ul><li>A collection of computers and devices connected by communications channels </li></ul><ul><li>Facilitates communications among users and allows users to share resources with other users </li></ul>p.9.11 Next share data and information facilitate communications share hardware share software
  23. 23. Networks <ul><li>What is a site license? </li></ul><ul><li>A legal agreement that allows multiple users to run a software package simultaneously </li></ul><ul><li>License fee usually is based on the number of users or the number of computers attached of the network </li></ul>p.9.11 Next
  24. 24. Networks <ul><li>What is a local area network (LAN)? </li></ul><ul><li>A network that connects computers and devices in a limited geographical area such as a home, school computer laboratory, office building, or closely positioned group of buildings </li></ul>p.9.12 Fig. 9-9 Click to view Web Link then click LAN Next
  25. 25. Networks <ul><li>What is a node ? </li></ul><ul><li>Each computer or device on a network </li></ul>p.9.12 node node node node node Next Often the nodes are connected to the LAN via cables A wireless LAN (WLAN) is a LAN that uses no physical wires
  26. 26. Networks <ul><li>What is a network operating system? </li></ul><ul><li>The system software that organizes and coordinates the activities on a local area network </li></ul><ul><li>Also called a network OS or NOS </li></ul>p.9.12 Administration Adding, deleting, and organizing users and performing maintenance tasks File management Locating and transferring files Next Printer management Prioritizing print jobs and reports sent to specific printers on the network Security Monitoring and, when necessary, restricting access to network resources
  27. 27. Networks <ul><li>How do some popular operating systems support networks ? </li></ul><ul><li>Many operating systems have built-in network features </li></ul><ul><li>In other cases, the network OS is a set of programs that works with another operating system(s) </li></ul>p.9.12 Fig. 9-10 Next
  28. 28. Networks <ul><li>What is a peer-to-peer LAN? </li></ul><ul><li>A simple, inexpensive network that typically connects less than 10 computers together </li></ul><ul><li>Each computer on a peer-to-peer network can share the hardware, data, or information located on any other computer in the network </li></ul><ul><li>Each computer stores files on its own storage devices </li></ul>p.9.13 Fig. 9-11 Next printer may be used by all computers on network network operating system and application software installed on each computer
  29. 29. Networks <ul><li>What is a client/server LAN? </li></ul><ul><li>A network in which one or more computers act as a server and the other computers on the network can request services from the server </li></ul>p.9.14 Fig. 9-12 Next client client client server laser printer
  30. 30. Networks <ul><li>What are servers and clients? </li></ul><ul><li>Server </li></ul><ul><ul><li>Controls access to the hardware and software on the network </li></ul></ul><ul><ul><li>Provides a centralized storage area for programs </li></ul></ul><ul><ul><li>Dedicated servers perform a specific task </li></ul></ul>p.9.14 <ul><li>Clients </li></ul><ul><ul><li>Other computers on the network </li></ul></ul><ul><ul><li>Rely on the server for resources </li></ul></ul>Next database server stores and provides access to a database network server manages network traffic print server manages printers and print jobs file server stores and manages files
  31. 31. Company on the Cutting Edge <ul><li>One of the leading personal computer makers </li></ul><ul><li>Second-largest computer seller </li></ul><ul><li>Initial success came from marketing IBM clones, look-alike computers that performed like the IBMs, but were less costly </li></ul>p.9.14 Click to view Web Link then click Compaq Next
  32. 32. Networks <ul><li>What is a wide area network (WAN)? </li></ul><ul><li>A network that covers a large geographic area using a communications channel that combines many types of media </li></ul><ul><li>Can be one large network or can consist of two or more LANs connected together </li></ul><ul><li>The Internet is the world’s largest WAN </li></ul>p.9.15 Fig. 9-13 Click to view Web Link then click Wide Area Network communications satellite Next
  33. 33. Networks <ul><li>What is an Internet use of peer-to-peer (P2P)? </li></ul><ul><li>An Internet network that enables users with the same networking software to connect to each other’s hard disks and exchange files directly </li></ul><ul><li>Napster and Gnutella are two examples of P2P </li></ul>p.9.16 Fig. 9-14 Next
  34. 34. Networks <ul><li>What is a metropolitan area network (MAN)? </li></ul><ul><li>A backbone network that connects local area networks in a metropolitan area such as a city or town </li></ul><ul><li>Handles the bulk of communications activity, or traffic, across that region </li></ul>p.9.14 Next
  35. 35. Networks <ul><li>What is a network topology? </li></ul><ul><li>The configuration, or physical arrangement, of the devices in a communications network </li></ul><ul><li>Networks usually use combinations of three topologies </li></ul>p.9.16 Next ring star bus
  36. 36. Networks <ul><li>What is a bus network? </li></ul><ul><li>Consists of a single central cable, to which all computers and other devices connect </li></ul><ul><li>The bus is the physical cable </li></ul><ul><li>The bus is also called the backbone </li></ul><ul><li>Inexpensive and easy to install </li></ul>p.9.17 Fig. 9-15 personal computer personal computer personal computer personal computer personal computer Next
  37. 37. Networks <ul><li>What is a ring network? </li></ul><ul><li>A cable forms a closed ring, or loop, with all computers and devices arranged along the ring </li></ul><ul><li>Data travels from device to device around the entire ring, in one direction </li></ul><ul><li>If a device fails, all the devices before the failed device are unaffected, but those after the failed device cannot function </li></ul>p.9.16 Fig. 9-16 Next
  38. 38. Networks <ul><li>What is a star network? </li></ul><ul><li>All of the devices connect to a central computer </li></ul><ul><li>The central computer is called the hub </li></ul><ul><li>All data that transfers from one computer to another passes through the hub </li></ul>p.9.17 Fig. 9-17 host computer printer file server personal computer personal computer personal computer personal computer Next
  39. 39. Networks <ul><li>What are network communications technologies? </li></ul><ul><li>Specific combinations of hardware and software that allow the different devices on several types of networks to be able to communicate </li></ul>p.9.18 Next Ethernet token ring TCP/IP WAP
  40. 40. Technology Trailblazer <ul><li>Robert Metcalfe </li></ul><ul><li>The inventor of Ethernet </li></ul><ul><li>Founder of 3Com Corporation </li></ul><ul><li>Former publisher and a current InfoWorld magazine columnist </li></ul><ul><li>He realizes the need for computer professionals to communicate their ideas clearly when they speak and write </li></ul>p.919 Click to view Web Link then click Robert Metcalfe Next
  41. 41. Company on the Cutting Edge <ul><li>Started in 1982 by Scott McNealy and three friends </li></ul><ul><li>Goal of building engineering workstations in the network computer model </li></ul><ul><li>The fastest-growing company in history based on revenue and the world’s second most profitable company </li></ul><ul><li>Builds the technology to power the Internet </li></ul>p.9.19 Click to view Web Link then click Sun Microsystems Next
  42. 42. Networks <ul><li>What is Ethernet? </li></ul><ul><li>A LAN technology that allows personal computers to contend for access to the network </li></ul><ul><li>Based on a bus topology, but can be wired in a star pattern </li></ul><ul><li>The most popular LAN because it is relatively inexpensive and easy to install and maintain </li></ul>p.9.19 Click to view Web Link then click Ethernet original Ethernet standard not very fast by today’s standards, but works well for small to medium networks Next Fast Ethernet transmits data and information at speeds up to 10 times faster than the original standard Gigabit Ethernet provides an even higher speed of transmission, with speeds up to 10 times faster than Fast Ethernet
  43. 43. Networks <ul><li>What is token ring? </li></ul><ul><li>A LAN technology that controls access to the network by requiring that network devices share or pass a special signal, called a token </li></ul><ul><li>A token is similar to a ticket </li></ul><ul><li>The device with the token can transmit data over the network </li></ul><ul><li>Only one token exists per network </li></ul><ul><li>Based on a ring topology, although it can use a star topology </li></ul>p.9.19 Next
  44. 44. Networks <ul><li>What is TCP/IP? </li></ul><ul><li>Short for transmission control protocol/Internet protocol </li></ul><ul><li>A technology that manages the transmission of data by breaking it up into packets </li></ul><ul><li>Commonly used for Internet transmissions </li></ul>p.9.19 Click to view Web Link then click TCP/IP Next packets Data is divided into small pieces called packets routers Devices that direct packets along the fastest available path packet switching Technique of breaking a message into packets, sending the packets, and then reassembling the data
  45. 45. Networks <ul><li>What is the Wireless Applications Protocol (WAP)? </li></ul><ul><li>Allows wireless mobile devices to access the Internet and its services such as the Web and e-mail </li></ul><ul><li>Uses a client/server network </li></ul><ul><li>The wireless device contains the client software, which connects to the Internet service provider's server </li></ul><ul><li>Devices that support WAP are called WAP-enabled devices </li></ul>p.9.20 Next
  46. 46. Networks <ul><li>An internal network that uses Internet technologies </li></ul><ul><li>Generally makes company information accessible to employees and facilitate working in groups </li></ul><ul><li>Typically also includes a connection to the Internet </li></ul><ul><li>What is an intranet? </li></ul>p.9.20 Next uses TCP/IP technologies has a Web server supports multimedia Web pages coded in HTML accessible via a Web browser users can post and update information on the intranet by creating and posting a Web page
  47. 47. Networks <ul><li>What is an extranet? </li></ul><ul><li>Allows customers or suppliers to access part of a company’s intranet </li></ul>p.9.20 Fig. 9-18 Next
  48. 48. Networks <ul><li>What is a firewall? </li></ul><ul><li>A general term that refers to hardware and/or software that restricts access to data and information on a network </li></ul>p.9.20 Fig. 9-19 personal computer personal computer personal computer personal computer personal computer personal computer personal computer printer firewall corporate network Internet Next
  49. 49. Networks <ul><li>What is a home network? </li></ul><ul><li>Multiple computers connected together in a home or home office </li></ul><ul><li>All computers in the house can </li></ul><ul><ul><li>connect to the Internet at the same time </li></ul></ul><ul><ul><li>access files and programs on the other computers in the home </li></ul></ul><ul><ul><li>share peripherals </li></ul></ul>p.9.22 Fig. 9-20 Click to view Web Link then click Home Networks Next
  50. 50. Networks <ul><li>What are four types of home networks? </li></ul>p.9.22 Ethernet network Requires you to connect a cable to each computer Next HomePLC (powerline cable) network Uses the same lines that bring electricity and power into your home Plug one end of a cable into the computer's parallel port and the other into a wall outlet Phoneline network Uses existing telephone lines Connect one end of a cable in the computer and the other end into a telephone jack Does not interfere with voice and data transmissions on the telephone lines HomeRF (radio frequency) network Uses radio waves, instead of cables, to transmit data
  51. 51. Networks <ul><li>What is an intelligent home network? </li></ul><ul><li>Extends the basic home network to include features such as lighting control, thermostat adjustment, and a security system </li></ul>p.9.23 Next
  52. 52. Communications Software <ul><li>What is communications software? </li></ul><ul><li>Consists of programs that help you establish a connection to another computer or network </li></ul><ul><li>Manages the transmission of data, instructions, and information </li></ul><ul><li>For two computers to communicate, they must have compatible communications software </li></ul><ul><li>Often, separate communications programs on your computer each serve a different purpose </li></ul>p.9.23 Next
  53. 53. <ul><li>A type of communications software that helps you establish a connection to another computer on the Internet using wizards, dialog boxes, and other on-screen messages </li></ul>Communications Software <ul><li>What is the Internet Connection Wizard? </li></ul>p.9.23 Fig. 9-21 Step 1: Start the Internet Connection Wizard. Step 2: Enter the telephone number of your ISP. Step 3: Enter user name and password to log on to the ISP. Step 4: Type the connection name to display on your desktop. Step 5: Click the Finish button to establish Internet connection. Next
  54. 54. Communications Software <ul><li>How do you access the Internet? </li></ul><ul><li>Enter a user name and password into a communications software dialog box to connect to an ISP </li></ul>p.9.24 Fig. 9-22 Next
  55. 55. Communications Software <ul><li>What is file transfer protocol (FTP)? </li></ul><ul><li>An Internet standard that allows you to upload and download files to and from a Web server, called the FTP server </li></ul><ul><li>An anonymous FTP site allows anyone to transfer files </li></ul><ul><li>Other sites require a specific username and password to access the FTP server </li></ul>p.9.24 Fig. 9-23 Click to view Web Link then click FTP Programs FTP logon information Next connection established files on your computer files on the FTP server
  56. 56. The Telephone Network <ul><li>What is the public switched telephone network (PSTN)? </li></ul><ul><li>The worldwide telephone system that handles voice-oriented telephone calls </li></ul>p.9.25 Fig. 9-24 satellite Click to view animation Next most of the PSTN uses digital technology analog signal analog signal final link from local telephone company to home or office
  57. 57. The Telephone Network <ul><li>What is a dial-up line? </li></ul><ul><li>A temporary connection that uses one or more analog telephone lines for communications </li></ul><ul><li>Not permanent </li></ul><ul><li>A modem at the sending end dials the telephone number of a modem at the receiving end </li></ul>p.9.25 Disadvantage Cannot control the quality of the connection because the telephone company’s switching office randomly selects the line Next Advantages Costs no more than making a regular call Computers at any two locations can establish a connection using modems and the telephone network
  58. 58. The Telephone Network <ul><li>What is a dedicated line? </li></ul><ul><li>A connection that always is established between two communications devices </li></ul><ul><li>The quality and consistency of the connection is better than a dial-up line because dedicated lines provide a constant connection </li></ul>p.9.25 Next Can be analog or digital Digital lines transmit data and information at faster rates than analog lines
  59. 59. The Telephone Network <ul><li>What is transfer rate? </li></ul><ul><li>The speed with which a line carries data and information </li></ul><ul><li>The faster the transfer rate, the faster you can send and receive data and information </li></ul><ul><li>Usually are expressed as bits per second (bps) </li></ul>p.9.26 bits per second (bps) Next kilobits per second (Kbps) megabits per second (Mbps) gigabits per second (Gbps)
  60. 60. The Telephone Network <ul><li>What are popular types of digital dedicated lines? </li></ul><ul><li>ISDN </li></ul><ul><li>DSL </li></ul><ul><li>T-carrier </li></ul><ul><li>ATM </li></ul>p.9.26 Fig. 9-25 Next
  61. 61. The Telephone Network <ul><li>What is an ISDN line? </li></ul><ul><li>Integrated Services Digital Network </li></ul><ul><li>A set of standards for digital transmission of data over standard copper telephone lines </li></ul><ul><li>Telephone line can carry three or more signals at once, through the same line using a technique called multiplexing </li></ul>p.9.26 Next Both ends require an ISDN modem Faster and clearer connections than standard telephone connections
  62. 62. The Telephone Network <ul><li>What is DSL? </li></ul><ul><li>Digital subscriber line </li></ul><ul><li>Transmits at fast speeds on existing standard copper telephone wiring </li></ul><ul><li>Some installations can be used for both voice and data </li></ul><ul><li>Requires a special network card or DSL modem </li></ul><ul><li>ADSL (asymmetric digital subscriber line) supports faster transfer rates when receiving data than when sending data </li></ul>p.9.26 Fig. 9-26 Click to view Web Link then click DSL Next
  63. 63. <ul><li>What is a T-carrier line? </li></ul><ul><li>Any of several types of digital lines that carry multiple signals over a single communications line </li></ul><ul><li>Uses a technique called multiplexing so that multiple signals can share the telephone line </li></ul><ul><li>Provides extremely fast data transfer rates </li></ul><ul><li>Usually only affordable by medium to large companies </li></ul>The Telephone Network p.9.27 Next T3 line 28 times faster than T1 Used for the Internet backbone T1 line Most popular
  64. 64. The Telephone Network <ul><li>What is asynchronous transfer mode (ATM)? </li></ul><ul><li>A service that carries voice, data, video, and multimedia at extremely high speeds </li></ul><ul><li>Predicted to become the Internet standard for data transmission </li></ul>p.9.27 the Internet Next telephone networks other networks with large amounts of traffic
  65. 65. Communications Devices <ul><li>What is a communications device? </li></ul><ul><li>Any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device </li></ul><ul><li>Sometimes the device must convert the data, instructions, and information from analog to digital signals or vice versa </li></ul>p.9.27 Next dial-up modems ISDN and DSL modems cable modems network interface cards
  66. 66. Communications Devices <ul><li>What is a modem? </li></ul><ul><li>A communications device that converts a computer's digital signals to analog signals before they are transmitted over standard telephone lines </li></ul><ul><li>Sometimes called a dial-up modem </li></ul>p.9.28 Click to view Web Link then click Modems Next mo dulate To change into an analog signal dem odulate To convert an analog signal into a digital signal mo + dem
  67. 67. Communications Devices <ul><li>What are internal and external modems? </li></ul><ul><li>external modem </li></ul><ul><ul><li>a stand-alone (separate) device </li></ul></ul><ul><ul><li>attaches to a special serial port on a computer </li></ul></ul><ul><ul><li>a standard telephone cord connects to a telephone outlet </li></ul></ul><ul><li>Internal modem </li></ul><ul><ul><li>A card that you insert into an expansion slot on a computer's motherboard </li></ul></ul><ul><ul><li>A standard telephone cord attaches between a port on the modem and the telephone outlet </li></ul></ul>p.9.28 Fig. 9-27 Next
  68. 68. Communications Devices <ul><li>What is a digital modem? </li></ul><ul><li>One that sends and receives data and information to and from a digital telephone line such as ISDN or DSL </li></ul>p.9.28 DSL modem Sends and receives digital data and information to a DSL line Next ISDN modem Also called an ISDN adapter Sends and receives digital data and information from your computer to an ISDN line
  69. 69. Communications Devices <ul><li>What is a cable modem? </li></ul><ul><li>A modem that sends and receives data over the cable television (CATV) network </li></ul><ul><li>Currently much faster than a dial-up modem or ISDN </li></ul><ul><li>Usually attaches to a USB port or a port on a network interface card </li></ul>p.9.29 Fig. 9-28 Click to view Web Link then click Cable Modems Next
  70. 70. Communications Devices <ul><li>What is a network interface card (NIC)? </li></ul><ul><li>Also called a LAN adapter </li></ul><ul><li>A card you insert into an expansion slot of a personal computer or other device, enabling the device to connect to a network </li></ul><ul><li>Works with a particular network technology </li></ul><ul><li>Available for desktop and mobile computers </li></ul>p.9.29 Fig. 9-29 Click to view Web Link then click Network Interface Cards NIC for desktop computer NIC for notebook computer Next
  71. 71. Communications Devices <ul><li>What is a hub? </li></ul><ul><li>A device that provides a central point for cables in a network </li></ul>p.9.30 Fig. 9-30 Next
  72. 72. Communications Channel <ul><li>What is a channel? </li></ul><ul><li>The communications path between two devices </li></ul>p.9.31 Click to view Web Link then click Bandwidth Bandwidth Width of the communications channel The higher the bandwidth, the more data and information the channel can transmit Next Transmission media Materials or techniques capable of carrying one or more signals When you send data from your computer to another device, the signal carrying the data most likely travels over a variety of transmission media
  73. 73. Communications Channel <ul><li>What is a typical communications channel? </li></ul>p.9.31 Fig. 9-31 Step 1: Sending device requests information using either a physical transmission media or a wireless transmission media. sending device modem ISP microwave station Step 2: When the request leaves the ISP, it travels over T1 lines, microwave stations, earth-based stations, and communications satellites until it reaches the Internet backbone. mainframe computer T1 lines earth-based stations communications satellite T1 lines Next Step 3: The request travels over T3 lines along the Internet backbone. T3 lines mainframe computer T3 lines Internet backbone Step 4: The request travels over T1 lines until it reaches the destination network server. T1 lines destination network server
  74. 74. Communications Channel <ul><li>What are characteristics of transmission media? </li></ul>p.9.32 Next <ul><li>baseband versus broadband </li></ul><ul><li>Baseband media can transmit only one signal at a time </li></ul><ul><li>Broadband media can transmit multiple signals simultaneously </li></ul><ul><li>physical versus wireless </li></ul><ul><li>Physical transmission media use wire, cable, and other tangible materials </li></ul><ul><li>Wireless transmission media send communications signals though the air or space </li></ul>
  75. 75. Physical Transmission Media <ul><li>What is physical transmission media? </li></ul><ul><li>Wire, cable, and other tangible (touchable) materials used to send communications signals </li></ul>p.9.32 Fig. 9-32 Next
  76. 76. Physical Transmission Media <ul><li>What is twisted-pair cable? </li></ul><ul><li>Consists of one or more twisted pair wires bundled together </li></ul><ul><li>Each twisted pair wire consists of two separate insulated copper wires </li></ul><ul><li>Twisted together to reduce noise </li></ul><ul><li>Noise is an electrical disturbance that can degrade communications </li></ul>p.9.33 Fig. 9-33 twisted pair cable twisted pair cable twisted pair wire Next
  77. 77. Physical Transmission Media <ul><li>What is coaxial cable? </li></ul><ul><li>Consists of a single copper wire surrounded by at least three layers </li></ul><ul><li>Often called coax </li></ul><ul><li>Often used for cable television wiring </li></ul>p.9.33 Fig. 9-34 coaxial cable plastic outer coating woven or braided metal insulating material copper wire Next
  78. 78. Physical Transmission Media <ul><li>What is fiber-optic cable? </li></ul><ul><li>Contains a core of dozens or hundreds of thin strands of glass or plastic </li></ul><ul><li>Uses light to transmit signals </li></ul><ul><li>Each strand is called an optical fiber </li></ul><ul><ul><li>Thin as a human hair </li></ul></ul>p.9.34 Fig. 9-35 fiber-optic cable between floors of a building cable contains many optical fibers outer covering jacket Next protective coating glass cladding optical fiber core
  79. 79. Physical Transmission Media <ul><li>What are the advantages and disadvantages of fiber-optic cable? </li></ul>p.9.34 Next <ul><li>Disadvantages </li></ul><ul><li>Costs more than wire </li></ul><ul><li>Can be difficult to install and modify </li></ul><ul><li>Advantages </li></ul><ul><li>Able to carry significantly more signals than wire </li></ul><ul><li>Faster data transmission </li></ul><ul><li>Less susceptible to noise from other devices </li></ul><ul><li>Better security for signals during transmission </li></ul><ul><li>Smaller size </li></ul>
  80. 80. Wireless Transmission Media <ul><li>What is wireless transmission media? </li></ul><ul><li>Send communications signals through the air or space </li></ul><ul><li>Used when it is inconvenient, impractical, or impossible to install cables </li></ul>p.9.34 Fig. 9-36 Click to view video Next
  81. 81. Wireless Transmission Media <ul><li>What is broadcast radio? </li></ul><ul><li>A wireless transmission medium that distributes radio signals through the air over long distances such as between cities, regions, and countries and short distances such as within an office or home </li></ul><ul><li>Slower and more susceptible to noise than physical transmission media </li></ul>p.9.35 transmitter sends the broadcast radio signal Next receiver accepts the broadcast radio signal must have an antenna that is located in the range of the signal transceiver both sends and receives signals from wireless devices
  82. 82. Wireless Transmission Media <ul><li>What is Bluetooth ™ ? </li></ul><ul><li>Uses short-range radio waves to transmit data among Bluetooth ™-enabled devices </li></ul><ul><li>Device contains a small chip that allows it to communicate with other Bluetooth™- enabled devices </li></ul>p.9.35 Fig. 9-37 Step 1: A customer buys a movie ticket over the Web and downloads it to a handheld computer. Step 1 Step 2 Step 2: The handheld computer stores a “proof-of-purchase voucher.” Step 3 Step 3: A Bluetooth™-enabled reader scans the voucher. Next Step 4: The customer is admitted to the movie theatre. Step 4
  83. 83. Wireless Transmission Media <ul><li>What is an example of a wireless local area network? </li></ul>p.9.36 Fig. 9-38 switch access point Next
  84. 84. Wireless Transmission Media <ul><li>What is cellular radio? </li></ul><ul><li>A form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cellular telephones </li></ul><ul><li>A cellular telephone is a telephone device that uses radio signals to transmit voice and digital data messages </li></ul>p.9.36 Fig. 9-39 mobile telephone switching office (MTSO) cell cell cell cell calling party in auto called party public switched telephone network base station (microwave station) Next
  85. 85. Wireless Transmission Media <ul><li>What is Personal Communications Services (PCS)? </li></ul><ul><li>A set of technologies used for completely digital cellular devices </li></ul><ul><li>Include handheld computers, cellular telephones, pagers, and fax machines </li></ul><ul><li>Devices have wireless modems allowing you Internet access and e-mail capabilities </li></ul>p.9.37 Next
  86. 86. Wireless Transmission Media <ul><li>What are microwaves? </li></ul><ul><li>Radio waves that provide a high-speed signal transmission </li></ul><ul><li>Involves sending signals from one microwave station to another </li></ul>p.9.38 Fig. 9-40 Next
  87. 87. Wireless Transmission Media <ul><li>What is a microwave station? </li></ul><ul><li>An earth-based reflective dish that contains the antenna, transceivers, and other equipment necessary for microwave communications </li></ul><ul><li>Uses line-of-sight transmission </li></ul><ul><ul><li>Must transmit in a straight line with no obstructions between microwave antennas </li></ul></ul>p.9.38 Fig. 9-40 Next
  88. 88. Wireless Transmission Media <ul><li>What is a communications satellite? </li></ul><ul><li>A space station that receives microwave signals from an earth-based station, amplifies the signals, and broadcasts the signals back over a wide area to any number of earth-based stations </li></ul><ul><li>Transmission to a satellite is an uplink </li></ul><ul><li>Transmission from a satellite to an earth-based station is a downlink </li></ul>p.9.38 Fig. 9-41 Click to view video Next
  89. 89. Wireless Transmission Media <ul><li>What is infrared (IR)? </li></ul><ul><li>A wireless transmission media that sends signals using infrared light waves </li></ul><ul><li>Requires a line-of-sight transmission </li></ul><ul><li>Many computers and devices have an IrDA port that enables the transfer of data using infrared light rays </li></ul>p.9.39 Fig. 9-42 Click to view video Next
  90. 90. Summary of Communications and Networks <ul><li>Communications </li></ul><ul><li>Sending and receiving devices </li></ul><ul><li>Uses of communications technologies </li></ul><ul><li>Networks </li></ul><ul><li>Communications software </li></ul><ul><li>The telephone network </li></ul><ul><li>Communications devices </li></ul><ul><li>Communications channel </li></ul><ul><li>Physical transmission media </li></ul><ul><li>Wireless transmission media </li></ul>
  91. 91. Chapter 9 Complete