Error Correction

• Audio CD Error Correction
  How do compact disks deal with slight scratches and damage to the disk? Which side of a CD should you lay down on a desk? Well, Prof. Kuhn from the U of Washington may not answer that question but his lectures do cover Chapter 10 in some detail.

• About.com Bar Codes
  Information on bar coding from milk.com
• Bar Code History Page
  Everything you ever wanted to know about bar coding. What was the first item scanned in a grocery store that now resides at the Smithsonian Museum?
• Welcome to Freebarcodes.com
  Generate you own printable bar codes.

[Top]

Keeping Data Private

• What is Data Encryption?
  A site with a cool demo of real-time encryption of text.

• The Ideal Cipher
  An outstanding website by John Savard in Edmonton. It should be your first stop for serious crypto information. 
• Introduction to Cryptography
  SSH Communications Security is the "world-leading supplier of Internet security software for demanding network security solutions". This web site is a good primer written for business managers.
• e-Commerce Infrastructure and Processes
  These are lectures 9 & 10 by Prof. Michael Tse for his Final-Year Elective (EIE417) at Hong Kong Polytechnic University. A nice overview of public and private cryptography.
• Secure Sockets Layer
  A method to keep your private data secure while transferring files over the net. A good primer on data security in large networks.
• CIA to Mask Web Moves with SafeBoy
  No NetNanny or cookies for the CIA. Some Berkley grad students tried to prevent the Saudi's from blocking access to their website and created anonymous web surfing that would make any hacker happy. Now the CIA is giving them venture capital to use this technology themselves. You've got to love the irony.
• Web Security
  General hints and demos on maintaining security over the web. Has a cool page on choosing good passwords.
• File Encryption
  You can encrypt your files here and mark them with a password! Try all the different encryption algorithms.
• Public Key Cryptography
  Public Key Cryptography. A popular encryption program by RSA, a trusted name for web security.
• Cryptography -- PGP
  Pretty Good Privacy (PGP) caused quite a stir when it was first released. This Trinity College website details how it works. 
• Cryptologic Nooks and Crannies!
  Codasaurus.com has everything a crypto enthusiast might want.
• Cryptogram Helper Source Code
  Some nice java scripts to help crack simple cryptograms like you find in the Sunday paper.
• Decoding cryptograms shareware
  Written in Visual Basic by Ted Swirsky, this useful software can be registered for $10.
• Cryptography Research
  An exhaustive site with cool puzzles to solve and description of the major encryption standards in use today. Do your math and become a cryptanalyst.
• CryptoQuote- genetic coding
  A new and very useful algorithm for attacking difficult problems- genetic coding- is outlined here. Finding the "fittest" solution is a problem for all sorts of fields, not just cryptography.
• EFF Cooperative Computing Awards Press Release (Apr. 6, 2000)
  The Electronic Freedom Foundation's $50K award for the biggest prime number. And who said math doesn't pay.
• Electronic Sample Issue of The Cryptogram
  Starts with the Caesar alphabet (Rome wasn't decoded in a day when all you had was a papyrus) and moves on through time. 
• Decoding Nazi secrets @ NOVA online
  How did a group of mathematicians save thousands of Allied lives during WWII? By breaking the encrypted codes of the Japanese and Germans. Learn about the basics of cryptography, use a virtual ENIGMA machine, and decipher Playfair ciphers at this well-done site.
• NSA - NCM The HARVEST Exhibit
  Now that the NSA can exist in the light of day, take a look at their crypto deciphering machines from the 1950's  and other time periods. A fascinating intertwining of military history, American technology, and spy vs. spy stuff. 
• NSA - VENONA History Release 2
  An actual case history of breaking Soviet codes in 1942-43. Details Soviet operations in Washington DC during WWII. 
• Cracking the code in Operation Iraq Freedom
  Did the Brits have access to the twenty-year old encryption ciphers used in the British-made Racal Jaguar V military radios that  Sadaam Hussein purchased in 1988? If so, it might explain one way they knew where to target bunker-buster bombs in Baghdad since cell phones were no longer used by the Iraqi's to communicate.
• Rijndael: The Advanced Encryption Standard
  The new block cipher standard proposed in 2001 for the federal government comes from the Netherlands. Complexity wrapped in an enigma folded into... well, you get the idea. 
•  Wheatstone's Playfair cipher
  Uses a 5x5 matrix to decipher messages.
•  Help on Constructing and decoding Playfair ciphers
  > Science Daily "The Playfair Cipher"
  > The Black Chamber's Playfair Cipher creator
  > PBS "Decoding Nazi Secrets"
   

[Top]    

Steganography

• Slashdot: The Rise of Steganography
  Good overview from the website of choice for the computing community. 
• Bin Laden: Steganography Master
  The hottest topic in cryptography today is being used by the bad guys as well. 
• Secret Messages Come in .Wavs
  George Mason University professor's research in how to conceal information in MP3's during the compression of a .wav file. The NSA even certifies his graduate program. 
• Steganography Outline: Hiding in plain sight
  The same Georgetown professor's own website and intro to information camouflage. 
• Wired 7.07 What Does It Do?
  A fun little puzzle that makes a great lecture kick-off. Make sure you print it off so it will fill up an entire sheet of paper. Just don't ask for the answer ;-).
• Beyond 2000 Cyberlife-Communications Mark My Words
  An easy-to-follow overview of digital watermarking to protect intellectual property rights.
• Hashed Music
  The technique known as "hashing" creates short chunks of encrypted code to represent longer, more complex signals. By hashing the sound signals of popular music you can create a searchable database of tunes that can be reached via a web-enabled cell phone. Your Nokia can now tell you the name of the muzak at the mall!
• Affine Resistant Digital Audio Watermarking Using Template Matching
  "A novel approach for embedding a digital watermark inaudibly into an audio clip, in the time domain...a binary image provided by the copyright owner". Ding-Yun Chen at the National Taiwan University proposes a way to watermark an audio file with an image. Sample .wav's are provided.
• Secure Digital Music Initiative (SDMI) by the Recording Industry Assoc. of America
  The need to stop audio piracy has led to many different schemes that employ some form of steganography to "watermark" the downloaded music as legal. The SDMI proposal would have hardware manufacturers detect this watermark before playing an mp3 file. Most folks have definite opinions on this technology.
• The watermark wars
  Brian Livingston at Infoworld.com describes how the battle to distinguish purchased music from other copies has made academic speech one of its casualties.

Digital Filters & Processing of Signals

• DSP in Practice
  A very useful site for DSP. Contains tutorials, demos and FAQs on filtering, images, university sites, software, books etc.
• Technical Paper Signal Processing Fundamentals
  Dennis Bohn at HeadWize has written an introduction to signals from an audio engineer's viewpoint. Written at an intro college level, the technical issues in making a great stereo sound system are detailed here. Lots of filter info here.
• FIR Digital Filters
  Demo of various digital filters on user defined signals. A great site to see a visual real-time effect of filtering.
• Info on Sound
  Canada Science and Technology Museum website. Whole bunch of information on sound.
• New Scientist Tuning in
    A personal earpiece with a DSP that can quiet or sharpen various sounds in a noisy environment. Parties nor combat will ever be the same again.
• Speech Codecs
  Listen to industry standard speech coding rates. Speech codecs are characterized by subjective tests on people.
• A/D Speech Demos
  Digitizing an analog signal. Listen to digitized versions of speech.
• Air chaining
  A clear and detailed tutorial on how to setup wireless links for the remote broadcasting of radio. Digital filtering is also covered.

[Top]

Digital Communication Channels

• Digital Transmission primer at Williams College
  This CS 105 reference site covers transmission media  and multiplexing in a clear and concise manner.
• Computer Networks and Internets
  Douglas Comer at Purdue has an excellent website to accompany his book. The animations of networking protocols and multiplexing are worth the visit.

[Top]

The Wireless World

• Origins of Wireless Communications
  A brief history of how radio transmission was invented and the developments till date
• Guglielmo Marconi
  The first person to transmit voice without wires!
• Samuel Morse
  Without this intelligent code, telegraphy would have been difficult indeed.
• Heinrich Hertz
  Heinrich Hertz showed that electromagnetic waves could be used to transmit information over distances.
• Alexander Graham Bell
  The father of the modern telephone instrument. An inventor and a true engineer.
• Wireless options primer
  This large Adobe Acrobat .pdf details all the possible ways an entity (like the county public safety dispatch system) could go about getting wireless communication systems in place. Written for the county board, this easy to follow guide details technical, economical, and political issues surrounding  large-scale wireless deployment.

[Top]

Electromagnetic Fields

• Vibrating Charges- EM fields
  A great tutorial at the Physics 200 website on what actually causes EM waves to occur. 
• 2-Dimensional Oscillation Simulation
  A java applet that simulates wave behavior in a tank. Great visualization for the difficulties of good antenna design. 
• Beyond 2000 Science-Planet Earth Radio
  The earth and it's magnetic fields are sources of many radio signals. Listen in on your own planet's broadcasts.
• Interference Patterns Multimedia Activities
  The San Francisco based Exploratorium can always be counted on for clear explanations of physical phenomenon. Here the concept of wave interference is covered. Requires the Shockwave plug-in.
• Multimedia Activities on waves
  ExploreSciences' wave motion multimedia links are quite helpful.

[Top]

Cell phones & Cellular Networks

• Radio Controlled
  The PASS website examines the use of radio networks and the algorithms behind cell phone transmissions.
• How Voice Processing Will Change the Web
  Will 3rd Generation (3G) cell phones (you've probably have a 2G phone) allow voice-activated surfing of the web? Industry standards are outlined here. 
• Stealth Jets Unmasked
  What might happen if cell phone technology was to render Stealth technology visible? It's happening... 
• Time Domain Corporation
  The holders of the UltraWideband technology patents, this company is using wireless in a completely novel way that will have profound consequences for society. Imagine personal broadband access unhindered by interference. Imagine radar-like flashlights that can see through buildings. The government has.
• Ultra Wide Band Implications
  Is it possible that there could be 10,000 different cable companies in town at some point? It could happen if you deliberately use noise to send signals.
• Ultra Wide Band Basics
  A nice primer on this digital picosecond-based protocol.
• Adaptive Antenna Technology
  ArrayComm makes smart antennas for "intelligent" cells (i-BURST�) that note the strength and direction of each cell phone and then work to optimize that signal's reception by allocating resources in that direction.
• Technology Review - Wireless Triple Play
  A new wireless antenna design to help boost overall performance.
• Technology Review - The Universal Cell Phone
  To boost cell phone reliability in congested networks software is fixing the gaps left by hardware issues.
• German design site for 3rd Generation phones
  What might you be able to do if your phone was Wireless Application Protocol (WAP) enabled? See some of the hopeful "killer apps" being proposed by these German grad students.
• Nokia Mobile Phones
  The leader in mobile phones. Makes some funky looking cell phones and networking equipment.
• Texas Instruments Wireless
  A little known fact, TI is a leader in special purpose chips required in the cell phones used today and essential for the fancy phones of the future.

[Top]

Wireless Standards & Applications

• 10Meters.com: Bluetooth vs 802.11
  The two major standards for low power wireless networks are compared side-by-side.
• Wired 9.04 The Hot New Medium Paper
  Combine a bluetooth ready pen, a tiny CCD camera, and special paper covered with a tiled system of nearly invisible dots and you've got Anoto. Imagine having all your class notes uploaded and stored via your telephone.
• BBC Online - BBC Digital Radio
  The "Beeb" is planning 5 new national digital radio stations in Britain.
• Cutting Edge Bedside Internet Radios- ABC News
  3Com's Kerbango Internet radio is the vanguard of new broadcast technologies.
• DAB: the Digital Radio in Canada The Canadians have a national program to roll out DAB in the next few years. TI is developing low-cost chip sets for this.  
• Digital radio for dummies
  One of the very best sites to understand this technology from a British broadband company. They also have the "Anorak's Guide to Digital Radio" which must be Brit for "geek speak".  
• Air chaining
  A clear and detailed tutorial on how to setup wireless links for the remote broadcasting of AM/FM radio.
• Stop, watch time for ratings in minute detail
  The American family watches so much TV they now can't (or won't) properly fill-out the AC Nielsen rating logbooks detailing their viewing habits. How will the networks know how many eyeballs are glued to their shows? Swatch's new wireless watch will be able to hear what you can't (or won't) write down... 

[Top]

The Electromagnetic Spectrum

• Electromagnetic Spectrum - Introduction
  NASA's "Imagine the Universe" site gives an easy visual overview of the EM spectrum.
• Internet Engineering Task Force
  An international network, spanning the entire world requires a dedicated team of professionals to keep it working smoothly. The volunteers at IETF ensure that when you click on a link, you can see the page stored thousands of miles away in a jiffy!
• International Telecommunications Union
  The international body specifying standards on a variety of communications equipment. This ensures a phone bought in Europe will work (at least on paper!) as well in the USA.
• Federal Communications Commission
  The US government agency responsible for laying down electrical transmission standards for the US territories. See this spectrum map where frequency bands are allocated for different applications.
• Spectrum map of EM spectrum allocations in the US
  Where does your cell phone broadcast in the microwave area? What patches of the spectrum are reserved for weather satellites? Take a walk through how Robert Maxwell's invisible country has been carved up in the US.
• The British RadioCommunications Agency 
    The UK version of our own FCC.
• Anybody Got Some Spare Spectrum?
  The political difficulties the FCC is having in freeing up space in the EM spectrum for new wireless technologies.

[Top]

Image Display Technologies

• Cathode Ray Tubes
  How does a TV and those large power-hungry computer monitors work? Here are several sites to help explain how shooting electron beams at a phosphorus-coated screen makes images:
  > Physics 2000- the TV: This easy-to-follow web site has excellent java scripts and animations. The best place to start.
  > The TV @ HowStuffWorks.com: Starting with how your brain processes vision and ending with electromagnets, this is a more in-depth tutorial.

• Liquid Crystal Displays
  > Physics 2000- the LCD screen: Again, the best starting spot for a discussion of polarized light and image display.
  > The LCD screen @ HowStuffWorks.com: A more detailed and accurate view of how cholesterol crystals (really!) are embedded in your laptop computer's screen. How do they make the brightness and resolution so high (and does that relate to their cost??!)?

• Digital Mirror Devices
  > Texas Instruments created the Digital Mirror Device (DMD), an extraordinary engineering innovation that is sure to change the way movies are shot and viewed in the future as these chips are incorporated into Digital Light Projectors (DLP's).
  > Delivering Digital Movies
  Pixar and QBit software are teaming up to deliver compressed digital movies on hard drives to theatres. You can see their efforts at the Spring Creek Cinema on I-75 in Plano, Texas. Digital cinema cameras start this all digital process.

• Plasma Displays
  > Plasma Displays @ HowStuffWorks.com:  An alternative flat panel display to LCD's, this technology has been showing up in high-end HDTV's.

• Light Emitting Diodes (LED's)
  > Jumbotron LED Displays @ HowStuffWorks.com: How can you watch TV with 60,000 of your closest friends? Count on Light Emitting Diodes to be able to give you a bright enough display to see at noon during your favorite ballgame.
  > Organic LED's (O-LED) create roll-up computer screens: Set for a 2005 debut, plastic tubes could unwrap and display images thanks to these flexible, organic ink-based light-emitting polymers. Imagine a true digital papyrus scroll (trivia: this was the best sfx prop in the movie
  "Red Planet" besides the robot).
  > Organic LED flexible screen developments
  > Toshiba O-LED flexible screens
  > Sarnoff Research in the US works on flex screen displays
  > O-LED's current state of development at Optics.org
  > Mobile phone in UK uses an O-LED screen (10/2002)

[Top]

Image Capture Technologies

• CCD Cameras @ HowStuffWorks.com: When you make the jump to a digital camera, how does this silicon retina convert your image to pixels? Take a look.
• 24P Digital movie cameras: With the advent of better digital imaging, directors like George Lucas are now shooting movies and not transferring to analog film, but dumping digital data onto hard drives or digital tape for editing later. Data Transfer rates of 100Mbs are a minimum requirement with storage in the tens to hundreds of Gigabytes per unit. BTW- "24P" stands for "24 Frame Progressive High Definition" cameras.
  > Star Wars: Episode II to use a 24P digital camera ( 4/2000)
  > Panasonic HD Cinema Camera Debuts (1/2001)
  > Digital Acquisition: Technology in Transition. How is lower cost ($4000) digital cameras of cinema quality changing how movies are made? (3/2002)
  > Be Like George-24p Camera under $3500!! Panasonic Debuts 24p Mini-DV Camcorder with "CineSwitch" (10-30-02 press release).

[Top]

Imaging Companies

• Hewlett Packard Scanners
  Just one of the companies making desktop scanning and printing devices. Color scanners and printers are essential transducers in digital image processing.
• Kodak DLC
  Kodak has been at the forefront of imaging technology, right from the first chemical film processes. A very exhaustive site describing every step of the process in a digital imaging system.
• Medialink Worldwide, Inc.
  An example of a company built on providing video services and tracking over the internet. What do they know when you watch the streaming BMW films?
• Digital Light Projector Papers
  Adobe acrobat files from TI.
• Philips Medical Imaging
  A major player in the medical imaging business. Digital imaging techniques have enabled medical practitioners faster and more effective diagnostic means. Magnetic Resonance Imaging (MRI) is just one such technology.

[Top]

Bandwidth & Network Design

• Fiber Crosses the 10-Trillion-Bit Barrier  NEC March 2001. This is what we all will have someday, right? Now if we can just find enough content to fill up the bandwidth. "500 channels and nothing's on" will eventually give way to capacities for downloading the entire library of congress in a snap- and hoping there is still somehting worth reading within all of those choices.
• Emerging Digital Communication Technologies
  A high-level overview of the issues involved with building better (digital) networks.

[Top]

Digital Storage

• Compact Disc Digital Audio (CDDA)
  A brief discussion of the Red Book Audio CD standard and such things as ripping and MP3's.
• How DVDs and DVD Players Work
  Howstuffworks.com's explanation of Digital Versatile Disks.
• How Hard Drives Work
  Howstuffworks.com's explanation of the most ingenious of magnetic media
• Multimedia Virtual Disk drive Design Studio
  This free UC Berkeley offering (funded by hard drive makers) from a few years ago (designing a 1.2 Gb drive!) teaches engineering principles and design trade-offs while walking students through hard drive component choices. Requires several class periods to walk through the entire tutorial.
• Scientific American Feature Article: How a Hard Disk works
  A nice graphic of how the stack of magnetic platters in your hard drive actually work. This is from an article that discusses how to bypass the ultimate physical barrier for storing data in magnetic domains- the superparamagnetic effect. 
• Storage Technologies at PCTechGuide
  From hard drives to optical, this straightforward guide to personal computing technologies has extensive essays on the hardware of data capture, retention, and delivery.
• Flash memory- How your SD or CF cards work
   Howstuffworks.com's explanation of the solid state memory you can now carry on your key ring. Goodbye floppies!
• Holographic memory comes into production
  In February of 2004, Nippon Telegraph and Telephone Corporation announced the achievement of postage stamp-sized plastic media with 1 GB memory capacity.
• Data Density Comparisions
  How many bits per area can engineers encode into a physical medium? Take a look at this comparison from 2003.

[Top]

General Reference & Tutorials

• How Things Work
  A very useful general purpose website that answers everyday questions on Science and much more.
• Encyclopedia Britannica
  A mine of information on just about anything you wanted to know!
• Welcome to Popular Science.com
  If you enjoy the magazine you'll find more content on this website.
• The NIST Reference on Constants, Units, and Uncertainty
  Uncertain about metric units and measurements in science? Visit the home of the atomic clock at the National Institutes of Standards and Technology and get help with conversions.
• Scientific American's Web Awards
  These winners are tops in their respective categories. If you need science help, look here first.

[Top]

Tutorials

• John Hopkins' Signal Processing Demonstrations
  A library of java applets that cover a wide range of topics covered in this course. A great tutorial page.
• Rice's DSP link library
  A comprehensive set of links for all items relating to the deeper study of signal processing.
• Applet Thumbnails from Einstein's Legacy
  If you want to see some of the best java applets on the WWW then visit the Physics 2000 website. Two U of Colorado at Boulder Nobel Prize Winners for Physics have created great visualizations for the technology that the basic understanding of the atom has led us to develop.
• Intro to Electronics
  Graham Knott's homepages are dedicated to tutorials on the basics like components, block diagrams, digital circuits, and more.
• Interactive Physics and Math with Java
  The University of Hawaii has placed all of it's java applets for physics and math at this site. A great place for visualizations of sinusoids and waves.
• Signal Processing Information Base (SPIB)
  The IEEE's own knowledge base for signal processing. What the professionals turn to when they have a question.
• Web ProForum: Network Tutorials All Sorted by Tutorial Title
  This web site contains the latest tutorials on various network topics authorized by numerous corporations, from TI to Cisco Systems. 
• Wheatstone Bridges
  How to calculate the value of an unknown resistance? Look here at the circuit first used by Lord Wheatstone in 1843 (though never claimed to be invented by him).

[Top]

Computing References