Protect Your PC from Viruses with the McAfee VirusScan! ©2004 SupraSite(tm) all rights reserved.		Welcome to SuprasiteTM Computers & Networks Introduction History Fundamentals Information Environment Digital Technology LAN Networks Other Digital Technology Description ·         Analog vs. Digital ·         Digital Imaging ·         Digital Communications ·         Digital Transport Services Description In this chapter you'll learn about... ·         The differences between analog and digital systems ·         How digital systems have changed the way things work Voice Over There's a lot to learn about digital systems and this chapter will familiarize you with some key concepts. Description Answer the following statement: Digital technology is new. ·         True                                                                                <Link to 0503> ·         False                                                                               <Link to 0503> Description Answer the following statement: Digital technology is new. ·         True ·         False This statement is false! Native Americans used binary smoke signals of short puffs and long puffs. Telegraphs and light signals on boats as well as Morse code are all composed of long and short signals. It's the implementation of digital transmission that is relatively new. Voice Over We know from Chapter 2's history lesson that the ideas behind digital technology are old, but digital transmission is new. Description Now answer the following statement: Digital is better than Analog. ·         True                                                                                <Link to 0505> ·         False                                                                               <Link to 0505> Description Now answer the following statement: Digital is better than Analog. ·         True ·         False Sorry, this was a trick question! Actually, both have their place... Description For instance, consider which of the following recording mediums has better quality and fidelity:          {Diagram: LP and Analog wave} ·         LP Phonograph album (plastic media with a needle) {Diagram: CD and Digital dots} ·         Compact Disc (plastic/aluminum media with a laser) Although you might argue that the CD has better fidelity, many musicians will argue that digital recording has a certain cold quality as compared to analog. Other Sound Music: scratchy record - 1920s style (ala Rudy Valle) music if possible Description What are some examples of 'Analog' Information? ·         Sound ·         Music ·         Sine Waves And what exactly are 'Sine Waves?' Description   SINE WAVE Carrier Wave                                                        time   Sine Waves A sine wave is a period uniform wave often generated by an object that vibrates at a single frequency such as a tuning fork or a crystal. Here is what a sine wave looks like... Description Wave Characteristics Amplitude (height) = Volume Peak Voltage Frequency (Width of One Complete Rotation) = Pitch (How often wave repeats itself) {Diagram: Carrier Wave} Here is an example which shows you the various properties of a sine wave, also known as a Carrier Wave. Now let’s discuss digital versus analog information in an office environment. Voice Over Digital systems have simplified and streamlined many processes. Description Analog transmission of a fax Digital transmission of a fax {Diagram: Analog fax vs. Digital fax} Digital systems provide users with enhanced image distribution capability.  Digital documents can be coded, in ASCII or bit map form, and sent to another digital device (such as a computer or fax). Analog documents can only be handled manually.  This offers the user fewer options and it’s slow.  For example, when you fax an analog letter, the fax machine transforms the letter into a digital format first so it can be transformed into a signal that can be sent over electrical wires. Description The Analog Problem {Diagram: Analog problem - attenuation} As you can see from the diagram above, analog does not offer a consistent repeatable signal. As the wave of sound or information is transmitted it becomes weaker and weaker and degenerates. When the weak signal is amplified, the amplifier boosts the degenerated wave which may have lost some of its initial character and the repeated signal will suffer. This is called Attenuation. Description The Digital Solution {Diagram: digital repeater} Digital signals can be repeated with more clarity and fidelity. This is because the amplifier is boosting a series of pre-determined numbers, not a changeable wave signal. Now that we have looked at the differences between analog and digital, let's look at how digital systems are used in imaging. Description Digital technology in imaging allows you to perform functions that analog technology cannot.  These functions can be classified into three groups: Image Manipulation ·         With a digital system featuring a scanner, computer and printer, users have almost limitless image manipulation selection.  Images can be bolded, moved, cropped and colors can even be modified. Output Image Quality ·         Is enhanced with a digital system because they scan and measure literally thousands of individual points of an original.  For example, analog copiers interpret the image as a whole and don’t pick up the fine detail that a digital copier does. Output Image Integrity ·         In a digital system, there isn’t any loss of resolution when you modify the original image (rearrange digital “on” and “off” signals.)  With an analog copier the quality of the image drops because photocopiers use a lens to distort the original image. How does it work? Let’s look at the basics.... Voice Over Digital technology has many benefits in terms of flexibility and quality. Description ANALOG Analog copiers reflect light from original image to a photoconductor using lenses and mirrors. Much light is lost in the process, therefore, copy is of lesser quality. DIGITAL Digital copiers convert reflected light into digital 1s and O’s which are sent to a photoconductor via a laser. Because the laser is a concentrated light source it produces better copy quality.  A digital copier can also change the image and create a new document. Let's take a closer look at each of these processes. Voice Over And digital technology has many benefits, especially in the imaging industry. Description Analog {Diagram: Analog photocopier} The initial steps in the analog system involve optical processes as the image is exposed and reflected onto the photoconductor through a lens. The second half of the process is the same as a digital system that you will see on the next page: development, separation, transfer-cleaning, fusing, and clenching Voice Over The analog system relies on an optical process. Description Digital {Diagram: Digital photocopier} The initial steps in the digital system involve electronic processes as the image is scanned into a controller and projected onto the photoconductor through a laser. The second half of the process is the same as the analog system. Voice Over The digital system relies on an electrical process. Description Digital Copiers vs. Laser Printers Although digital copiers produce quality work, they have received a bad rap. When customers speak about their copiers, they say words and phrases like, "jammed, high service, not reliable." When they speak about their laser printers, they say, "highly reliable." Interestingly, laser printers use the same process as digital copiers; the only difference is the volume that each is expected to produce. If you compare the number of copies produced versus the number of printouts produced annually, the service calls on a copier don't seem so unreasonable! In addition, a laser printer drum is changed every time the printer cartridge is changed. Voice Over Copiers often  get a bad rap because they are unfairly compared to printers which don't take as much abuse. Description Some of the benefits found in Digital Imaging are ·         Copy Quality - Concentrated light source (high resolution) Superior gray scale ·         Versatility - Since image is digitized, easy manipulation (zoom, R/E, editing) can be done. ·         Economical - Cost versus functions ·         Multifunctional - Digita lization allows for one product to have many capabilities. Copier, fax, Printer, Scanner ·         Interaction - Digital equipment can interface with other office equipment and function in a connected (network) environment ·         Space Savings - One compact unit takes less space than four separate systems Now that we've looked at Digital Imaging, let's look at Digital Communications. Voice Over Digital Copiers offer improved quality, versatility and economy. Description There are several standard processes in digital communications that you should be familiar with. They are ·         PCM (Pulse Code Modulation) ·         TDM (Time Division Multiplexing) ·         E/O (Electrical to Optical Converter) Voice Over Digital communication offers a whole new range of connectivity methods and terms. Description PCM (Pulse Code Modulation) PCM was developed to perform conversion from Analog signals to Digital signals. PCM works on a scale from +127 to -127. And it is done through a three step process: {Diagram: flow chart of the following 3 steps} 1) Sampling 2) Quantizing 3) Encoding These are described on the following pages. Voice Over PCM, or Pulse Code Modulation, converts Analog to Digital and Digital back to Analog. Description PCM - Sampling {Diagram: The sampling process} Sampling measures an analog signal and marks where the line hits either above or below the median line with a dot 8,000 times per second. Description PCM - Quantizing {Diagram: Quantized numbers} Quantizing simply means a signal is rounded off to the nearest whole number. This way points are labeled with whole number values. Description PCM - Encoding {Diagram: Encoding Process} Encoding takes values and turns them into binary coded numbers. For instance, the whole numbers - 95, 93, and 81 - need to be expressed for transmission. As we learned in the section on Binary Code in Chapter 3: Computer Fundamentals, these would be encoded as follows: 95=0101111 93=0101101 81=01010001 and sent along their way. Description TDM (Time Division Multiplexing) {Diagram: TDM see page 5-17} Remember back in Chapter 1 where we discussed how humans multitask (perform multiple instructions at the same time, but computers perform one task at a time in a certain sequence. Well, Time Division Multiplexing (TDM) is just the kind of 'slice and dice' process that a computer does to perform multiple tasks at once on a T1 line. TDM refers to a method where 24 different signals are sampled one at a time and a piece of each of these signals is sent (1, 2, 3, 4...through 24) along a wire. After the first pass of signals is done, a 'framing bit' lets the system know it has finished the piece of signal #24 and is ready to start over again at 1. A framing bit is like a downbeat in music and is thrown in at the end of the 24th transmission to insure that if a bit between 1-24 gets lost, only one is corrupted. The system starts fresh with each pass through of the 24 signals. The computer does this 8,000 times per second or 64,000 bits per second. Voice Over TDM, or Time Division Multiplexing, allows computers to sample and send more signals at a time. E/O (Electrical to Optical Converter) The Electrical to Optical Converter process is used with fiber optic lines and works by converting binary code pulses into light pulses. {Diagram: Bill, the wire and the flashlight} {Animate: Bill gets electrocuted and the flashlight flicks on and off} In order to better understand how this process works, imagine a guy (we'll call him 'Bill') has a wire in one hand and a flashlight in the other. Every time Bill gets a jolt of electricity on his wire hand, he flicks the flashlight in the other hand on for a second. Voice Over E/O, or Electrical to Optical Conversion, is used in fiber networks. Description {Diagram: Flow chart - the three methods in a chain - PCM/TDM to E/O to O/E to TDM/PCM} In long distance digital communications a combination of all three of these processes may be used. This is because optical signals do not need to be repeated as often as electrical signals. Voice Over Long distance communications use all three of these methods. Description Bandwidth The speed and breadth of the digital communication channel is referred to as bandwidth.  The bandwidth for an average phone line is 64 Kb. Let's look at additional types of Digital Transport Services that offer increased bandwidth. Description There are several types of digital transport services available. Click on any of these transport services to learn more ·         T1                                                                                   <Link to 0529> ·         T2-4                                                                                <Link to 0530> ·         ISDN                                                                              <Link to 0531> ·         DSL                                                                                <Link to 0532> ·         Point-to-point                                                               <Link to 0533> ·         FDDI                                                                              <Link to 0534> Voice Over It seems that everyday there is a new type of digital transport service. Here are some currently available. Other Sound Button click for all buttons. Description There are several types of digital transport services available. Click on any of these transport services to learn more ·          T1                                                                                   ·          T2-4                                                                                <Link to 0530> ·          ISDN                                                                                <Link to 0531> ·          DSL                                                                                 <Link to 0532> ·          Point-to-point                                                                 <Link to 0533> ·          FDDI                                                                               <Link to 0534> T1 ·         A private leased line ·         Point-to-point ·         Supports Voice, Video and Data ·         Consists of twenty-four, 64 Kilobits Per Second lines A capability of 1.544 Mbps Per Second ·         Can be fractionalized i.e.- 1, 2, 4, 8 or 12 lines out of 24 ·         Typically requires up to six hours of usage per day to be cost effective Other Sound Button click for all buttons. Description There are several types of digital transport services available. Click on any of these transport services to learn more ·          T1                                                                                   <Link to 0529> ·          T2-4                                                                                ·          ISDN                                                                                <Link to 0531> ·          DSL                                                                                 <Link to 0532> ·          Point-to-point                                                                 <Link to 0533> ·          FDDI                                                                               <Link to 0534> T2-4 T1s may be combined to increase bandwidth. T2 - four T1s                                                                         6.312 Mbps T3 - seven T2s                                                                      44.736 Mbps (Currently fastest line available uses twisted pair cable) T4 - some multiple of T1s Description There are several types of digital transport services available. Click on any of these transport services to learn more ·          T1                                                                                   <Link to 0529> ·          T2-4                                                                                <Link to 0530> ·          ISDN                                                                                ·          DSL                                                                                 <Link to 0532> ·          Point-to-point                                                                 <Link to 0533> ·          FDDI                                                                               <Link to 0534> ISDN (Integrated Services Digital Network) ·         Allows users to send voice, video and data over a single phone line ·         Physically consists of two sets of two wires (send and receive) ·         Requires an NT-1 (Network Termination) device Two standard configurations of ISDN lines are: ·         BASIC RATE INTERFACE (BRI or 2B+D) Slower Dial Up variety of ISDN (Consists of two 56 or 64 KBPS ‘bearer’ channels and one 16 KBPS ‘data’ channel). ·         PRIMARY RATE INTERFACE (PRI or 23B+D) Higher speed Leased Line ISDN (Consists of twenty-three 56 or 64 KBPS ‘bearer’ channels and one 56 or 64 KBPS ‘data’ channel =T1 line). Description There are several types of digital transport services available. Click on any of these transport services to learn more ·          T1                                                                                   <Link to 0529> ·          T2-4                                                                                <Link to 0530> ·          ISDN                                                                                <Link to 0531> ·          DSL                                                                                 ·          Point-to-point                                                                 <Link to 0533> ·          FDDI                                                                               <Link to 0534> DSL (Digital Subscriber Line) ·         A Technology that allows users to send and receive voice, video and data using the existing copper telephone lines without the need for amplifiers or repeaters. ·         Requires a DSL terminating device at each end of the cable pair. DSL comes in several flavors: ·         ADSL – Asymmetric Digital Subscriber Line – Takes its name from the high bandwidth in one direction, with low bandwidth in the opposite direction. Uses a single phone line for transmission and has ability to operate up to 8 Mbps positions for applications like Web Surfing, File Downloads, and Distance Learning. ·         ADSL-Lite or g.lite – Has a “downstream” data rate of 1.5 Mbps or less. Low cost for consumer use. ·         HDSL – High-bit-rate Digital Subscriber Line – Older technology which allows for data transmission in both directions over two copper loops. HDSL receivers can transmit 2.084 Mbps data signal at a distance up to 13k ft. without repeaters. ·         HDSL2 – Next generation of DSL with data transmission in both directions using a pair of copper lines. Other Sound Button click for all buttons. Description There are several types of digital transport services available. Click on any of these transport services to learn more ·          T1                                                                                   <Link to 0529> ·          T2-4                                                                                <Link to 0530> ·          ISDN                                                                                <Link to 0531> ·          DSL                                                                                 <Link to 0532> ·          Point-to-point                                                                 ·          FDDI                                                                               <Link to 0534> Point-to-point It is typically an older connection that may be mentioned by older IS networking people. ·         Speeds (Kilobits Per Second) - 2.4, 4.8, 9.6, 19.2, 56, 64 ·         Name (Sample) -DIGITAL DATAPHONE SERVICE (DDS), SYNCHRONET SERVICE, ACCUNET/SWITCHED 56/SWITCHED 64 ·         Transports digital bit streams between two binary language devices (PCs, Minis, Mainframes, G4 faxes) ·         Does not require a modem ·         Requires a CSU/DSU (Channel Service Unit/Data Service Unit) at both ends of channel service unit/digital service unit (digital transport facility) ·         Does not convert digital to analog or vice-versa. Used to terminate, supervise and monitor the digital line ·         CSU/DSU functionality can be built directly into the office product ·         Low volume digital transport (small files): 2.4 KBPS or 4.8 KBPS ·         High volume digital transport for large files or many small consolidated files: 56, 64 KBPS or 1.544 Mbps Description There are several types of digital transport services available. Click on any of these transport services to learn more ·          T1                                                                                   <Link to 0529> ·          T2-4                                                                                <Link to 0530> ·          ISDN                                                                                <Link to 0531> ·          DSL                                                                                 <Link to 0532> ·          Point-to-point                                                                 <Link to 0533> ·          FDDI                                                                                 FDDI (Fiber Distributed Data Interface) ·         One of the latest digital communication transport service ·         Provides a backbone of communications services across town or within a building ·         Has a digital speed of 100 Megabits per second and was designed to work with Fast Ethernet ·         Limited to about 60 miles of cable (no repeaters) ·         Companies can economically install FDDI systems for their own use Companies sometimes rent these backbone services to other businesses in the neighborhood or, if within a building, as LAN wiring alternatives for floor-to-floor connectivity Other Sound Button click for all buttons. Description More About Transport Services {Diagram: Chart for ISDN lines projection} It is interesting to look at this industry forecast number for ISDN lines in the U.S. Actually these early forecasts were wrong due to changes in technology and the advent of other types of digital transport services such as cable modems and especially DSL. Source:  Computer Industry Forecasts Navigation Bar Options Home Help Terms Quiz Feedback Quit Menu Previous Summary Next 0000 0003 1300 1400 email Exit 0500 0528 0599 0536 0536 Chapter Title Digital Technology Screen Title Digital Transport Services Screen Shot Description Comparison of Data Communication Speed {Diagram: chart of ISDN vs. DSL} With advent of DSL, the rate of implementation for ISDN has slowed considerably compared to earlier projected rates. Users thirst for faster Internet access is attributed to this shift. Description ·         Analog information is made up of sine waves that we can hear, like sound, music, telephones, human speech. ·         Digital information is a binary (1s and 0s) representation of images, text, voice and characters. ·         Digital technology offers better quality, faster transmission speeds and the ability to manipulate and change information. ·         All information technology is moving towards digital because of these benefits. ·         Digital communications will continue to get more cost effective, and provide cost effective solutions (G4 facsimile). ·         Current and future digital products will be connected to networks in increasing numbers in order to provide flexibility in inputting, distributing, sharing and outputting an ever increasing volume of complex information within your customer’s organization. Voice Over As we learned in Chapter 3 computers deal with 1s and 0s, and digital technology supports this working system. As the speed and ability of technology increases, we can look forward to more cost effective, quality communications and imagery.
		Suprasite (tm) copyright 1994-2005 all rights resevered. | hosted by itempo.com | designed by homecamp.com