How Cell-phone Viruses Work

The first known cell-phone virus appeared in 2004 and didn't get very far. Cabir.A infected only a small number of Bluetooth-enabled phones and carried out no malicious action -- a group of malware developers created Cabir to prove it could be done. Their next step was to send it to anti-virus researchers, who began the process of developing a solution to a problem that promises to get a lot worse.
Cell-phone viruses are at the threshold of their effectiveness. At present, they can't spread very far and they don't do much damage, but the future might see cell-phone bugs that are as debilitating as computer viruses. In this article, we'll talk about how cell-phone viruses spread, what they can do and how you can protect your phone from current and future threats.

Cell-phone viruses currently target Symbian Series 60 phones with Bluetooth and MMS capabilities, like this Nokia 6620.

Cell-phone Virus Basics

A cell-phone virus is basically the same thing as a computer virus -- an unwanted executable file that "infects" a device and then copies itself to other devices. But whereas a computer virus or worm spreads through e-mail attachments and Internet downloads, a cell-phone virus or worm spreads via Internet downloads, MMS (multimedia messaging service) attachments and Bluetooth transfers. The most common type of cell-phone infection right now occurs when a cell phone downloads an infected file from a PC or the Internet, but phone-to-phone viruses are on the rise.
Current phone-to-phone viruses almost exclusively infect phones running the Symbian operating system. The large number of proprietary operating systems in the cell-phone world is one of the obstacles to mass infection. Cell-phone-virus writers have no Windows-level marketshare to target, so any virus will only affect a small percentage of phones.
Infected files usually show up disguised as applications like games, security patches, add-on functionalities and, of course, pornography and free stuff. Infected text messages sometimes steal the subject line from a message you've received from a friend, which of course increases the likelihood of your opening it -- but opening the message isn't enough to get infected. You have to choose to open the message attachment and agree to install the program, which is another obstacle to mass infection: To date, no reported phone-to-phone virus auto-installs. The installation obstacles and the methods of spreading limit the amount of damage the current generation of cell-phone virus can do.

That Thing With Paris Hilton's Phone
Remember when someone got his hands on Paris Hilton's star-studded contact list? It was not the result of a virus, and nobody hacked into Hilton's phone.
Mobile phone servers hold on to certain types of information, such as contact lists (in case the user's phone locks up) and recent calls (for billing purposes). The enterprising hacker got into T-mobile's servers and stole the information from there.

How They Spread

Phones that can only make and receive calls are not at risk. Only smartphones with a Bluetooth connection and data capabilities can receive a cell-phone virus. These viruses spread primarily in three ways:
Internet downloads - The virus spreads the same way a traditional computer virus does. The user downloads an infected file to the phone by way of a PC or the phone's own Internet connection. This may include file-sharing downloads, applications available from add-on sites (such as ringtones or games) and false security patches posted on the Symbian Web site.
Bluetooth wireless connection - The virus spreads between phones by way of their Bluetooth connection. The user receives a virus via Bluetooth when the phone is in discoverable mode, meaning it can be seen by other Bluetooth-enabled phones. In this case, the virus spreads like an airborne illness. According to TechnologyReview.com, cell-phone-virus researchers at F-Secure's U.S. lab now conduct their studies in a bomb shelter so their research topics don't end up spreading to every Bluetooth-enabled phone in the vicinity.
Multimedia Messaging Service - The virus is an attachment to an MMS text message. As with computer viruses that arrive as e-mail attachments, the user must choose to open the attachment and then install it in order for the virus to infect the phone. Typically, a virus that spreads via MMS gets into the phone's contact list and sends itself to every phone number stored there.
In all of these transfer methods, the user has to agree at least once (and usually twice) to run the infected file. But cell-phone-virus writers get you to open and install their product the same way computer-virus writers do: The virus is typically disguised as a game, security patch or other desirable application.
The Commwarrior virus arrived on the scene in January 2005 and is the first cell-phone virus to effectively spread through an entire company via Bluetooth (see ComputerWorld.com: Phone virus spreads through Scandinavian company). It replicates by way of both Bluetooth and MMS. Once you receive and install the virus, it immediately starts looking for other Bluetooth phones in the vicinity to infect. At the same time, the virus sends infected MMS messages to every phone number in your address list. Commwarrior is probably one of the more effective viruses to date because it uses two methods to replicate itself.
So what does a virus like this do once it infects your phone?

The Damage Done

The first known cell-phone virus, Cabir, is entirely innocuous. All it does is sit in the phone and try to spread itself. Other cell-phone viruses, however, are not as harmless.
A virus might access and/or delete all of the contact information and calendar entries in your phone. It might send an infected MMS message to every number in your phone book -- and MMS messages typically cost money to send, so you're actually paying to send a virus to all of your friends, family members and business associates. On the worst-case-scenario end, it might delete or lock up certain phone applications or crash your phone completely so it's useless. Some reported viruses and their vital statistics are listed below.

Cell-phone Viruses

Cabir.AFirst reported: June 2004Attacks: Symbian Series 60 phonesSpreads via: BluetoothHarm: noneMore information (including disinfection): http://www.f-secure.com/v-descs/cabir.shtml
Skulls.AFirst reported: November 2004Attacks: various Symbian phonesSpreads via: Internet downloadHarm: disables all phone functions except sending/receiving callsMore information (including disinfection): http://www.f-secure.com/v-descs/skulls.shtml
Commwarrior.AFirst reported: January 2005Attacks: Symbian Series 60 phonesSpreads via: Bluetooth and MMSHarm: sends out expensive MMS messages to everyone in phonebook (in course of MMS replication)More information (including disinfection): http://www.f-secure.com/v-descs/commwarrior.shtml
Locknut.BFirst reported: March 2005Attacks: Symbian Series 60 phonesSpreads via: Internet download (disguised as patch for Symbian Series 60 phones)Harm: crashes system ROM; disables all phone functions; inserts other (inactive) malware into phoneMore information (including disinfection): http://www.f-secure.com/v-descs/locknut_b.shtml
Fontal.AFirst reported: April 2005Attacks: Symbian Series 60 phonesSpreads via: Internet downloadHarm: locks up phone in startup mode; disables phone entirelyMore information (including disinfection): http://www.f-secure.com/v-descs/fontal_a.shtml

As you can see from the above descriptions, cell-phone viruses have gotten a lot more harmful since the Cabir worm landed in the hands of researchers in 2004. But on the bright side, there are some steps you can take to protect your phone.

Protecting Your Phone

The best way to protect yourself from cell-phone viruses is the same way you protect yourself from computer viruses: Never open anything if you don't know what it is, haven't requested it or have any suspicions whatsoever that it's not what it claims to be. That said, even the most cautious person can still end up with an infected phone. Here are some steps you can take to decrease your chances of installing a virus:
Turn off Bluetooth discoverable mode. Set your phone to "hidden" so other phones can't detect it and send it the virus. You can do this on the Bluetooth options screen.
Check security updates to learn about filenames you should keep an eye out for. It's not fool-proof -- the Commwarrior program generates random names for the infected files it sends out, so users can't be warned not to open specific filenames -- but many viruses can be easily identified by the filenames they carry. Security sites with detailed virus information include:
F-Secure
McAfee
Symantec
Some of these sites will send you e-mail updates with new virus information as it gets posted.
Install some type of security software on your phone. Numerous companies are developing security software for cell phones, some for free download, some for user purchase and some intended for cell-phone service providers. The software may simply detect and then remove the virus once it's received and installed, or it may protect your phone from getting certain viruses in the first place. Symbian has developed an anti-virus version of its operating system that only allows the phone's Bluetooth connection to accept secure files.
Although some in the cell-phone industry think the potential problem is overstated, most experts agree that cell-phone viruses are on the brink of their destructive power. Installing a "security patch" that ends up turning your phone into a useless piece of plastic is definitely something to be concerned about, but it could still get worse. Future possibilities include viruses that bug phones -- so someone can see every number you call and listen to your conversations -- and viruses that steal financial information, which would be a serious issue if smartphones end up being used as payment devices (see Bankrate.com: Paying by cell phone on the way). Ultimately, more connectivity means more exposure to viruses and faster spreading of infection. As smartphones become more common and more complex, so will the viruses that target them.
For more information on cell-phone viruses and related topics, check out the links on the next page.

How Rail Guns Work

Gunpowder has long been the propellant of choice to launch a projectile from a weapon. But the fine gray powder does have three major limitations:
Gunpowder must be carried with the projectile, making the entire round heavier.
Ordnance based on black powder is volatile, and so difficult to handle and transport.
The muzzle velocity of projectiles propelled by gunpowder is generally limited to about 4,000 feet (about 1,219 meters) per second.
Photo courtesy Sam Barros of PowerLabsCAPTION-->
Is it possible to overcome these challenges? One solution is the electromagnetic rail gun, or rail gun for short. Using a magnetic field powered by electricity, a rail gun can accelerate a projectile up to 52,493 feet (16,000 meters) per second. And while current Navy guns have a maximum range of 12 miles, rail guns can hit a target 250 miles away in six minutes.
In this article, we'll discuss how rail guns work, how they can be used and the limitations of this technology.
Thank You
Thanks to Sam Barros of PowerLabs for his assistancewith this article. Sam, a Mechanical Engineering student at Michigan Technological University, has designed and built his own rail guns, coil guns and many other devices.

Rail Gun Basics
A rail gun is basically a large electric circuit, made up of three parts: a power source, a pair of parallel rails and a moving armature. Let's look at each of these parts in more detail.

The power supply is simply a source of electric current. Typically, the current used in medium- to large-caliber rail guns is in the millions of amps.
The rails are lengths of conductive metal, such as copper. They can range from four to 30 feet (9 meters) long.
The armature bridges the gap between the rails. It can be a solid piece of conductive metal or a conductive sabot -- a carrier that houses a dart or other projectile. Some rail guns use a plasma armature. In this set-up a thin metal foil is placed on the back of a non-conducting projectile. When power flows through this foil it vaporizes and becomes a plasma, which carries the current.
Here's how the pieces work together:
An electric current runs from the positive terminal of the power supply, up the positive rail, across the armature, and down the negative rail back to the power supply.

Current flowing in any wire creates a magnetic field around it -- a region where a magnetic force is felt. This force has both a magnitude and a direction. In a rail gun, the two rails act like wires, with a magnetic field circulating around each rail. The force lines of the magnetic field run in a counterclockwise circle around the positive rail and in a clockwise circle around the negative rail. The net magnetic field between the rails is directed vertically.
Like a charged wire in an electric field, the projectile experiences a force known as the Lorentz force (after the Dutch physicist Hendrik A. Lorentz). The Lorentz force is directed perpendicularly to the magnetic field and to the direction of the current flowing across the armature. You can see how this works in the diagram below.

Notice that the Lorentz force is parallel to the rails, acting away from the power supply. The magnitude of the force is determined by the equation F = (i)(L)(B), where F is the net force, i is the current, L is the length of the rails and B is the magnetic field. The force can be boosted by increasing either the length of the rails or the amount of current.
Because long rails pose design challenges, most rail guns use strong currents -- on the order of a million amps -- to generate tremendous force. The projectile, under the influence of the Lorentz force, accelerates to the end of the rails opposite the power supply and exits through an aperture. The circuit is broken, which ends the flow of current.
Usurping Power
Rail guns require tremendous currents to fire projectiles at speeds of Mach 5 or higher. This presents problems for a traditional battleship because power cannot be diverted from the ship's propulsion system. In the Navy's next-generation battleship, the all-electric DD(X), producing this kind of current will be possible. To launch a rail gun projectile, power would be diverted from the ship's engine to the gun turret. The gun would be fired, up to six rounds per minute, for as long as required. Then power would be shifted back to the engine.

Problems with Rail Guns

in theory, rail guns are the perfect solution for short- and long-range firepower. In reality, they present several serious problems:
Power supply:Generating the power necessary to accelerate rail gun projectiles is a real challenge. Capacitors must store electric charge until a sufficiently large current can be accumulated. While capacitors can be small for some applications, the capacitors found in rail guns are many cubic meters in size.
Resistive heating: When an electric current passes through a conductor, it meets resistence in the conductive material -- in this case, the rails. The current excites the rail's molecules, causing them to heat. In rail guns, this effect results in intense heat.
Melting: The high velocity of the armature and the heat caused by resistive heating damages the surface of the rails.
Repulsion: The current in each rail of a rail gun runs in opposite directions. This creates a repulsive force, proportional to the current, that attempts to push the rails apart. Because the currents in a rail gun are so large, the repulsion between the two rails is significant.
Wear and tear on rail guns is a serious problem. Many break after a few uses, and sometimes they can only be used once.
Rail Guns versus Coil Guns
A coil gun (or Gauss gun) is an electromagnetic launcher that offers a few advantages over rail guns. The "barrel" of a coil gun is a series of copper coils. These coils are energized sequentially, setting up a traveling magnetic field on the inside of the barrel. This magnetic field attracts a ferromagnetic projectile down the barrel. Since the projectile of a coilgun floats in the barrel and never touches the coils, it suffers less wear and tear, and these guns are completely quiet. Coil guns have been demonstrated to supersonic velocities, but they are not as efficient or as capable as railguns.

Rail Gun Applications

Rail guns are of particular interest to the military, as an alternative to current large artillery. Rail gun ammunition, in the form of small tungsten missiles, would be relatively light, easy to transport and easy to handle. And because of their high velocities, rail gun missiles would be less susceptible to bullet drop and wind shift than current artillery shells. Course correction would be important, but all missiles fired from rail gun artillery would be guided by satellite.
It would be more difficult to engineer small arm rail guns, mainly because of recoil. Recoil, the backward action of a firearm upon discharge, is determined by the momentum of the escaping projectile. Multiplying a projectile's mass by its velocity yields its momentum, which for high-velocity rail gun projectiles would be considerable. A portable rail gun that fires very small bullets may be the solution. A small bullet would limit recoil but still carry enough kinetic energy to inflict serious damage.
Photo courtesy ONRAn artist's conception of a U.S. Navy aircraft carrierequipped with a rail gun.
Rail guns have also been proposed as important components of the Strategic Defense Initiative, popularly known as Star Wars. Star Wars is a U.S. government program responsible for the research and development of a space-based system to defend the nation from attack by strategic ballistic missiles. Rail guns could fire projectiles to intercept the incoming missiles. Some scientists argue that rail guns could also protect Earth from rogue asteroids, by firing high-velocity projectiles from orbit. Upon impact, the projectiles would either destroy the incoming asteroid or change its trajectory.
Rail guns have some interesting non-military applications as well. For one thing, they could potentially launch satellites or space shuttles into the upper atmosphere, where auxiliary rockets would kick in. On bodies without an atmosphere, such as the moon, rail guns could deliver projectiles to space without chemical propellant, which requires air to function.
Photo courtesy Department of Defense Visual Information Center An artist`s concept of the interception and destruction of nuclear-armed re-entry vehicles by a space-based rail gun.
Rail guns could also be used to initiate fusion reactions. Fusion occurs when two small atomic nuclei combine together to form a larger nucleus, a process that releases large amounts of energy. Atomic nuclei must be traveling at enormous velocities for this to happen. On the earth, some scientists propose using rail guns to fire pellets of fusible material at each other. The impact of the high-velocity pellets would create immense temperatures and pressures, enabling fusion to occur.
Many of these applications remain in the realm of theory, experimentation and development. Current rail guns do not generate sufficient energies to enable nuclear fusion to occur, for example. And it will likely be 2015 before an all-electric battleship uses a rail gun to launch projectiles at an enemy.
Still, the technology is promising. In 2003, the British Ministry of Defense hosted a one-eighth-scale test of an electromagnetic rail gun that achieved a muzzle velocity of Mach 6, or approximately 2,040 meters per second.
With continued successes such as these, the rail gun may one day be the weapon of choice on the battlefield and the propellant of choice on the launch pad.
For lots more information on rail guns and related topics, check out the links on the next page.
The Science in Fiction
If rail guns seem tantalizingly familiar, it's because weapons based on similar principles have been featured prominently in popular culture. In Robert Heinlein's The Moon is a Harsh Mistress, lunar colonists, in a struggle for independence use an electromagnetic launcher to fire iron containers filled with rocks at Earth. In the movie "Eraser," Arnold Schwarzenegger stars as a Witness Protection agent who has stumbled on a secret government plot to sell rail guns to terrorists. And in "Battlestar Galactica," the museum-era warship is armed with rail guns that use both electromagnetic and conventional technologies.
These fanciful weapons have also found their way into video games. Rail guns are featured in "Quake", "Metal Gear Solid" and "Red Faction."

Lots More Information
Related HowStuffWorks Articles
How Electromagnets Work
How Electromagnetic Propulsion Will Work
How Shotguns Work
How Machine Guns Work
How Revolver Works
How Flintlock Guns Work
More Great Links
Rochester Institute of Technology
PowerLabs Rail Gun Research
Railguns on Absolute Astronomy
Office of Naval Research: Future Naval Capabilities

How Teleconferencing Works

In the past few years, corporations have gotten bigger and more spread out. Many American employees -- more than 44 million in 2004 -- also do at least some of their work from home [ref]. Since offices and employees can be thousands of miles apart, getting everyone into the same room for meetings and training has become decidedly impractical for a lot of companies.
That's why teleconferencing -- the real-time exchange of information between people who are not in the same physical space -- has become such a big industry. The American audio conferencing industry alone reported $2.25 billion in revenue in 2004 [ref]. Through teleconferencing, companies can conduct meetings, customer briefs, training, demonstrations and workshops by phone or online instead of in person.
In this article, we'll look at different types of teleconferencing, from conference calls to online meetings.

The Popular PolycomThe Polycom SoundStation is one of the most popular teleconferencing units available. You might have seen it in movies or on TV. Check it out.

Teleconferencing by Phone
Private Branch Exchange Businesses typically have a private branch exchange (PBX) within their offices. The PBX is a switched network of telephone connections inside the office. Each phone has an extension, and multiple phones share lines to the public switched telephone network (PSTN) outside. This is typically less expensive than running a dedicated telephone line to each extension, especially for larger businesses.
The simplest phone teleconference is a three-way call, available in many homes as a service from the telephone company. Another very simple (but not necessarily effective) method is to have two groups of people talk to one another via speakerphone. The limits of three-way calling and the sound quality of speakerphones make both of these options impractical for most businesses.
Conference calls let groups of people -- from a few to hundreds -- communicate by phone. Banks and brokerages often use conference calls to give status reports to large numbers of listeners. Other businesses use conference calls to help coworkers communicate, plan and brainstorm. To connect to the call, attendees call a designated number (MeetMe conferencing), or an operator or moderator calls each participant (ad hoc conferencing).
Conference calls connect people through a conference bridge, which is essentially a server that acts like a telephone and can answer multiple calls simultaneously. Software plays a large role in the bridge's capabilities beyond simply connecting multiple callers.
Photo courtesy -->CAPTION-->
A company can have its own bridge or can contract with a service provider for conference call hosting. Providers frequently offer add-on features for conference calls, such as:
Attendee polling
Call recording
In-call operators or attendants Companies using Voice over IP (VoIP) telephones can also host conference calls themselves if the VoIP software supports them.
Many phone conferencing systems require a login and personal identification number (PIN) to access the system. This helps protect confidential and proprietary information during the call.
Video phones can add a visual element to conference calls, but businesses often need to share other visual information. Next, we'll look at web conferencing and how it adds a visual element to long-distance meetings.

Teleconferencing Online
Web conferencing allows people to communicate through text and video in addition to audio. The simplest web conferencing methods use chat and instant messaging programs to host text-based group discussions. More sophisticated programs exchange visual information with webcams and streaming video. Some allow people to share documents online.
Companies can either purchase conferencing software and host their meetings themselves or use a hosting service. Hosting services provide the software and server space on which to conduct meetings. Either way, the company or the hosting service must have software to coordinate the meeting and ample server space and bandwidth to accommodate it.
Photo courtesy Premiere Global ServicesCAPTION-->
Web conferencing programs combine tools already common to web pages and Internet communication. They bundle these tools into one interface to create an interactive meeting environment. These tools include:
HTML, XML and ASP markup
Java scripts
Flash animation
Instant messaging
Streaming audio and video
Some programs are entirely computer- and Internet-based. Others use the telephone system to distribute audio content. To participate in the online meetings, participants must have:
A computer
An Internet connection
A telephone, if audio content is not provided online
If the conferencing program relies on Internet-based audio chat and webcam feeds, the participants' PCs should have:
Microphones
Webcams
Video capture cards
In general, every online presentation or meeting has a moderator and attendees. The moderator sets the time and date of the meeting, prepares the content and makes sure everything works properly before the meeting begins. Attendees can either view the presentation without giving feedback or can collaborate, based on the settings and capabilities of the programs. Often, moderators can record the presentation for later viewing and can pass their moderator capabilities to attendees during the meeting.
But what can people do in these virtual meeting rooms? Next, we'll look at some of the more common features in web conferencing programs.
Other Uses for Web Conferencing
Web conferences aren't just for businesses. Hospitals can use audio and video conferencing to supplement their emergency room staff. For example, some Massachusetts hospitals use video conferencing to allow neurologists to confer with stroke patients. Web conferencing has also allowed deployed soldiers to communicate with their families and even get married.

Web Conferencing Features
Web Conferencing TermsWebinar - An interactive seminar or presentation distributed online Webcast - A one-way audio or video presentation distributed online
Web conferencing programs come with a tremendous variety of features and capabilities. Some can merge with a company's existing e-mail, calendar, messaging and office productivity applications. Some allow attendees to view the presentation in their regular web browser without installing any additional software.
Depending on the software, people can:
View slide presentations from programs like PowerPoint
Draw or write on a common whiteboard by using their computer mice or typing
Annotate images and diagrams using the same whiteboard principle
Transmit still pictures or video to other attendees via a webcam (This increases the required bandwidth and can sometimes slow the transfer of the presentation.)
View information from the moderator's computer desktop using screen sharing
Share documents, often even if attendees don't have the software that created them, using application sharing
Hold interactive question-and-answer sessions that integrate video and audio
Send public or private messages through instant messaging
Annotate or modify documents and spreadsheets from compatible applications
Transfer files between attendees
Ask and answer questions through audio chat (as an integrated part of the software) or by phone
Photo courtesy -->Some web conferencing programscan replicate real-world whiteboards.
Since these meetings take place over the Internet, programs include options for security and encryption. Most programs require moderators and attendees to use a login name and password to access the meeting. Some use SSL or TLS encryption to protect data. Some companies also host web conferences on internal servers so that the data stays behind the corporate firewall. The moderator or host can monitor who is participating in the conference through sign-in logs and roll calls.
Next, we'll take a step-by-step look at how a typical online meeting takes place.

A Typical Online Meeting
Web conferences can vary dramatically depending on software, hosting and how the moderator runs the meeting. Here are the basic steps used with many meeting programs:
The moderator gathers content for the meeting, including spreadsheets, documents and presentations from other applications.
The moderator sets a time and date for the meeting and uses the meeting software to invite attendees via e-mail.
The attendees accept the invitation, and their calendar programs add the meeting to their calendars.
The meeting moderator opens the conferencing software before the meeting is scheduled to start and makes sure the connections and content are working properly.
When the meeting time arrives, the attendees click on the URL in their invitation email to go to the meeting.
The visual portion of the meeting takes place in the meeting software or in a web browser.
The moderator and participants communicate by phone, voice chat or instant messenger during the meeting.
At the end of the meeting, the moderator and attendees close their programs or browser windows and sign off.
For more information about telework, teleconferencing and related topics, check out the links on the next page.

Lots More Information
Related HowStuffWorks Articles
How Web Pages Work
How Java Works
How Web Animation Works
How Instant Messaging Works
How Firewalls Work
How Internet Radio Works
How Telephones Work
How Encryption Works
How Virtual Offices Work
How Setting Up a Home Office Works
More Great Links
Teleconferencing
Thinkofit Web Conferencing Guide
Conferencing News
ConferZone
A History of Video Conferencing

How Holographic Versatile Discs Work

Holographic memory systems have been around for decades. They offer far more storage capacity than CDs and DVDs -- even "next-generation" DVDs like Blu-ray -- and their transfer rates leave conventional discs in the dust. So why haven't we all been using holographic memory for years now?
There are several hurdles that have been holding holographic storage back from the realm of mass consumption, including price and complexity. Until now, the systems have required a cost-prohibitive level of precision in manufacturing. But recent changes have made the holographic versatile disc (HVD) developed by Optware a viable option for consumers.
In this article, we'll find out how the HVD works, how it has improved upon previous methods of holographic storage and how it stacks up to Blu-ray and HD-DVD.

Basics of Holographic Memory
Photo courtesy Wolfgang Wieser3-D image of the Death Star created by holographyThe first step in understanding holographic memory is to understand what "holographic" means. Holography is a method of recording patterns of light to produce a three-dimensional object. The recorded patterns of light are called a hologram.
The process of creating a hologram begins with a focused beam of light -- a laser beam. This laser beam is split into two separate beams: a reference beam, which remains unchanged throughout much of the process, and an information beam, which passes through an image. When light encounters an image, its composition changes (see How Light Works to learn about this process). In a sense, once the information beam encounters an image, it carries that image in its waveforms. When these two beams intersect, it creates a pattern of light interference. If you record this pattern of light interference -- for example, in a photosensitive polymer layer of a disc -- you are essentially recording the light pattern of the image.
To retrieve the information stored in a hologram, you shine the reference beam directly onto the hologram. When it reflects off the hologram, it holds the light pattern of the image stored there. You then send this reconstruction beam to a CMOS sensor to recreate the original image.
Most of us think of holograms as storing the image of an object, like the Death Star pictured above. The holographic memory systems we're discussing here use holograms to store digital instead of analog information, but it's the same concept. Instead of the information beam encountering a pattern of light that represents the Death Star, it encounters a pattern of light and dark areas that represent ones and zeroes.
Photo courtesy OptwareEncoded page data
Optware's HVD offers several advantages over traditional storage technology. HVDs can ultimately store up to 1 terabyte (TB) of information (although initial versions of the disc will feature a 200-gigabyte capacity) -- that's 200 times more than a single-sided DVD and 20 times more than a current double-sided Blu-ray. This is partly due to HVDs storing holograms in overlapping patterns, while a DVD basically stores bits of information side-by-side. HVDs also use a thicker recording layer than DVDs -- an HVD stores information in almost the entire volume of the disc, instead of just a single, thin layer.
Courtesy OptwareDVD vs. HVD: Recording-layer depth
Courtesy OptwareVolumetric recording method
The other major boost over conventional memory systems is HVD's transfer rate of up to 1 gigabyte (GB) per second -- that's 40 times faster than DVD. An HVD stores and retrieves an entire page of data, approximately 60,000 bits of information, in one pulse of light, while a DVD stores and retrieves one bit of data in one pulse of light.
Now that we know the premise at work in HVD technology, let's take a look at the structure of the disc.

The Holographic Versatile Disc
CompetitorsBesides Optware, there are several other companies racing to get their consumer-friendly holographic storage system to market. One product in the running is Inphase Technologies' Tapestry� disc. See InPhase Technologies to learn more.Holographic memory has been around for more than 40 years, but several characteristics made it difficult to implement in a consumer market. First off, most of these systems send the reference beam and the information beam into the recording medium on different axes. This requires highly complex optical systems to line them up at the exact point at which they need to intersect. Another drawback has to do with incompatibility with current storage media: Traditionally, holographic storage systems contained no servo data, because the beam carrying it could interfere with the holography process. Also, previous holographic memory discs have been notably thicker than CDs and DVDs.
Optware has implemented some changes in its HVD that could make it a better fit for the consumer market. In the HVD system, the laser beams travel in the same axis and strike the recording medium at the same angle, which Optware calls the collinear method. According to Optware, this method requires a less complex system of optics, enabling a smaller optical pickup that is more suited to consumer use.
Courtesy OptwareHVD optical pickup
HVD also includes servo data. The servo beam in the HVD system is at a wavelength that does not photosensitize the polymer recording medium. In the HVD test system, the servo data is carried in a red (650-nm wavelength) laser. The size and thickness of an HVD is also compatible with CDs and DVDs.
The structure of the disc places a thick recording layer between two substrates and incorporates a dichroic mirror that reflects the blue-green light carrying the holography data but allows the red light to pass through in order to gather servo information.
Because the HVD system is currently in the late stages of research and development, complete technical information is unavailable for public consumption. But in the next section, we'll discuss a simplified version of the system that covers the major aspects of HVD.

The HVD System: Writing DataA simplified HVD system consists of the following main components:
Blue or green laser (532-nm wavelength in the test system)
Beam splitter/merger
Mirrors
Spatial light modulator (SLM)
CMOS sensor
Photopolymer recording medium
The process of writing information onto an HVD begins with encoding the information into binary data to be stored in the SLM. These data are turned into ones and zeroes represented as opaque or translucent areas on a "page" -- this page is the image that the information beam is going to pass through.
Photo courtesy OptwareData image
Once the page of data is created, the next step is to fire a laser beam into a beam splitter to produce two identical beams. One of the beams is directed away from the SLM -- this beam becomes the reference beam. The other beam is directed toward the SLM and becomes the information beam. When the information beam passes through the SLM, portions of the light are blocked by the opaque areas of the page, and portions pass through the translucent areas. In this way, the information beam carries the image once it passes through the SLM.
When the reference beam and the information beam rejoin on the same axis, they create a pattern of light interference -- the holography data. This joint beam carries the interference pattern to the photopolymer disc and stores it there as a hologram.
Photo courtesy OptwarePage data (left) stored as a hologram (right)
A memory system isn't very useful if you can't access the data you've stored. In the next section, we'll find out how the HVD data-retrieval system works.

The HVD System: Reading DataTo read the data from an HVD, you need to retrieve the light pattern stored in the hologram.
In the HVD read system, the laser projects a light beam onto the hologram -- a light beam that is identical to the reference beam (Read System 1 in the image above). The hologram diffracts this beam according to the specific pattern of light interference it's storing. The resulting light recreates the image of the page data that established the light-interference pattern in the first place. When this beam of light -- the reconstruction beam -- bounces back off the disc (Read System 2), it travels to the CMOS sensor. The CMOS sensor then reproduces the page data.
Photo courtesy OptwarePage data stored in an HVD (left) and recreated by CMOS sensor (right)
Now let's take a look at how HVD compares to other next-generation storage media.

How HVD ComparesWhile HVD is attempting to revolutionize data storage, other discs are trying to improve upon current systems. Two such discs are Blu-ray and HD-DVD, deemed the next-generation of digital storage. Both build upon current DVD technology to increase storage capacity. All three of these technologies are aiming for the high-definition video market, where speed and capacity count. So how does HVD stack up?

Blu-ray
HD-DVD
HVD
Initial cost for recordable disc
Approx. $18
Approx. $10
Approx. $100
Initial cost for recorder/player
Approx. $2,000
Approx. $2,000
Approx. $3,000
Initial storage capacity
54 GB
30 GB
200 GB
Read/write speed
36.5 Mbps
36.5 Mbps
1 Gbps
Because HVD is still in the late stages of development, nothing is written in stone; but you've probably noticed that the projected introductory price for an HVD is a bit steep. An initial price of $100 per disc will probably be a big obstacle to consumers. However, this price might not be so insurmountable to businesses, which are Optware's initial target audience. Optware and its partners will market HVD's storage capacity and transfer speed as ideal for archival applications, with commercial systems available as soon as early 2006. Consumer devices could hit the market around 2010.
For more information on HVD and related topics, check out the links on the next page.

Lots More Information
Related HowStuffWorks Articles
How Bits and Bytes Work
How Blu-ray Discs Work
How DVDs Work
How Holographic Memory Works
How Lasers Work
How Light Works
More Great Links

InPhase Technologies: What is holographic storage?
Optware Corporation
Pro AV: What's Next: Pump up the Volume
The Register: Alliance touts holographic disc 'revolution'
Video/Imaging DesignLine: Holographic Storage Standards Eyed

How SMS Works

Just when we're finally used to seeing everybody constantly talking on their cell phones, it suddenly seems like no one is talking at all. Instead, they're typing away on tiny numerical pads, using their cell phones to send quick messages. SMS, or text messaging, has replaced talking on the phone for a new "thumb generation" of texters.
In this article, we'll find out how text messaging works, explore its uses and learn why it sometimes takes a while for your text message to get to its recipient.
What is SMS?
SMS stands for short message service. Simply put, it is a method of communication that sends text between cell phones, or from a PC or handheld to a cell phone. The "short" part refers to the maximum size of the text messages: 160 characters (letters, numbers or symbols in the Latin alphabet). For other alphabets, such as Chinese, the maximum SMS size is 70 characters.
But how do SMS messages actually get to your phone? If you have read How Cell Phones Work, you can actually see what is happening.
Even if you are not talking on your cell phone, your phone is constantly sending and receiving information. It is talking to its cell phone tower over a pathway called a control channel. The reason for this chatter is so that the cell phone system knows which cell your phone is in, and so that your phone can change cells as you move around. Every so often, your phone and the tower will exchange a packet of data that lets both of them know that everything is OK.
Your phone also uses the control channel for call setup. When someone tries to call you, the tower sends your phone a message over the control channel that tells your phone to play its ring tone. The tower also gives your phone a pair of voice channel frequencies to use for the call.
The control channel also provides the pathway for SMS messages. When a friend sends you an SMS message, the message flows through the SMSC, then to the tower, and the tower sends the message to your phone as a little packet of data on the control channel. In the same way, when you send a message, your phone sends it to the tower on the control channel and it goes from the tower to the SMSC and from there to its destination.
SMS AttacksRecently it has been suggested that SMS messages could be used to attack a cell phone system. Articles like this one discuss the problem. The basic idea is very simple. If a large number of SMS messages were sent by computers to phones in a small geographical area (like a city), these messages would overwhelm the control channels and make it impossible for the cell phone system to set up calls. Now that cell phone providers know about the possibility of this threat, they can design systems to throttle messages coming from the SMSC onto the network.

The actual data format for the message includes things like the length of the message, a time stamp, the destination phone number, the format, etc. For a complete byte-by-byte breakdown of the message format, see this page.
In the next section we'll learn about some of the uses and advantages of SMS.

Why 160 Characters?SMS was designed to deliver short bursts of data such as numerical pages. To avoid overloading the system with more than the standard forward-and-response operation, the inventors of SMS agreed on a 160-character maximum message size.
But the 160-character limit is not absolute. Length limitations may vary depending on the network, phone model and wireless carrier. Some phones don't allow you to keep typing once the 160-character limit is reached. You must send your message before continuing. However, some services will automatically break any message you send into chunks of 160 characters or less. So, you can type and send a long message, but it will be delivered as several messages.
Why use SMS?
Photo courtesy SOURCE
TEXT-->SMS has several advantages. It is more discreet than a phone conversation, making it the ideal form for communicating when you don't want to be overheard. It is often less time-consuming to send a text message than to make a phone call or send an e-mail. SMS doesn't require you to be at your computer like e-mail and instant messaging (IM) do -- although some phones are equipped for mobile e-mail and IM services. SMS is also a convenient way for deaf and hearing-impaired people to communicate.
SMS is a store-and-forward service, meaning that when you send a text message to a friend, the message does not go directly to your friend's cell phone. The advantage of this method is that your friend's cell phone doesn't have to be active or in range for you to send a message. The message is stored in the SMSC (for days if necessary) until your friend turns his cell phone on or moves into range, at which point the message is delivered. The message will remain stored on your friend's SIM card until he deletes it.
In addition to person-to-person messages, SMS can be used to send a message to a large number of people at a time, either from a list of contacts or to all the users within a particular area. This service is called broadcasting and is used by companies to contact groups of employees or by online services to distribute news and other information to subscribers.
In a 2004 University of Plymouth study on the psychology of SMS users, researchers found that mobile phone users were primarily either "texters" or "talkers" [ref]. Compared to the talkers, the texters sent nearly double the number of SMS messages and made less than half as many voice calls per month. The texters preferred SMS to voice calls for its convenience as well as for the ability to review a message before sending it.
Companies have come up with many uses for the service beyond just your typical person-to-person message. Because SMS doesn't overload the network as much as phone calls, it is frequently used by TV shows to let viewers vote on a poll topic or for a contestant. As a promotional tool, wireless carriers put up giant screens at concerts and other large-scale events to display text messages from people in the audience.
You can use text messaging subscription services to get medication reminders sent to your phone, along with weather alerts, news headlines or even novels broken into 160-character "chapters." Internet search engines such as Yahoo! and Google have short messaging services that enable users to get information such as driving directions, movie showtimes or local business listings just by texting a query to the search engine's phone number. Social networking services such as Dodgeball use SMS to alert people who live in big cities when their friends or crushes are nearby. The possibilities for integrating SMS into your lifestyle seem endless.
Naturally, SMS has limitations, and there are some people who feel it has outlived its usefulness. In the next section, we'll look at the disadvantages of SMS and some of the alternatives out there.
SMS HistorySMS was created during the late 1980s to work with a digital technology called GSM (global system for mobile communications), which is the basis for most modern cell phones. The Norwegian engineers who invented it wanted a very simple messaging system that worked when users' mobile phones were turned off or out of signal range. Most sources agree that the first SMS message was sent in the UK in 1992.
As SMS was born in Europe, it's not surprising that it took a little longer to make its way to the United States. Even today, texting enjoys much greater popularity in Europe, though its stateside use is on the rise. A July 2005 study found that 37 percent of U.S. mobile phone owners had sent or received at least one text message in the previous month [ref].
SMS Criticism and Alternatives
SMS in the NewsBecause of the impersonal nature of SMS, it raises certain questions of etiquette -- namely, what kind of information is OK to send in a text instead of delivering it in person? Recently, several people have sought legal action after they were fired or notified of divorce proceedings via SMS.
Broadcast text messages have been used to rally political activists in Beijing and to mobilize young people for riots in Belfast. Recently, a contest pitted the efficiency of SMS against Morse code (the Morse coders won).
Despite their popularity, short messaging services have recieved some criticism. Here are a few of the disadvantages:
You have to pay for it. Most wireless plans charge for a certain number of text messages a month. Some only charge for user-originated messages, while others charge for incoming messages as well. If you exceed your message allowance, you may be charged 10 cents per message, and those little charges can add up.
Speedy message delivery is not guaranteed. During periods of high traffic, it might be minutes or even hours before a message gets through.
It's strictly for sending text messages. SMS does not support sending pictures, video or music files. Alternative messaging services allow for more elaborate types of messages. With EMS (Enhanced Messaging Service), you can send formatted text, sound effects, small pictures and icons. MMS (Multimedia Messaging Service) allows you to send animations, audio and video files in addition to text. If your mobile phone is EMS- or MMS-enabled, you can use these standards just as you would SMS. However, the cost per message will be higher.
Another alternative to using SMS is using an instant messaging program, such as AOL IM, on your cell phone. This can be in the form of software that's pre-installed on your phone, or you can use WAP (Wireless Application Protocol) to access the Internet and sign into your IM account. WAP is a protocol that gives you small, simplified versions of web pages that are easily navigable on your mobile phone or PDA (check out How WAP Works for more information). You can use it to send instant messages or actual e-mails from your phone.
A common complaint about SMS is its inefficient delivery structure -- when the message center is backed up, messages take longer to reach their destination. To make message delivery faster, networks are using more new next-generation technologies such as GPRS (General Packet Radio Service).
To learn more about SMS and other forms of mobile communication, check out the links on the following page.
Lots More Information
Related HowStuffWorks Articles
How Cell Phones Work
How Cell-phone Viruses Work
How Radio Works
How Routers Work
How WAP Works
What does GSM mean in a cell phone?
What is a packet?
More Great Links

SMS Tutorial
SMS Forum
160 Characters
Textually.org
Dodgeball

its gona rock

How Nintendo Revolution Works

Imagine that you are one of the major video console manufacturers in the world. Everyone in the industry is selling approximately the same thing -- a console containing the processor along with a two-handed game controller. If you are in last place, what are you going to do to stand out?
One way to create a splash would be to totally blow out the amount of processor and graphics firepower. The problem is that both the Xbox 360 and the Playstation 3 have already staked out the high ground here. They have bleeding-edge multi-core chips.
So Nintendo took a different and far riskier path. First, it chose the codename "Revolution" for its new game console. Then the company set a big goal -- to dramatically improve the interface for video games. With this strategy, Nintendo built an amazing amount of hype around its innovative controller for the Revolution.
In this article, we'll take a close look at Nintendo's new console and interface. We'll also learn what makes the Revolution so incredibly different from other next-generation consoles and discuss some of the rumors and speculation about this prototype.
Changing the Interface
Photo courtesy HowStuffWorks ShopperNintendo GameCube controllerIf you look at the controllers for the Xbox, the Playstation 2 and the GameCube, you'll notice that they are nearly identical. You hold them in two hands and use your thumbs to control the in-game action with buttons, D-pads and joysticks. Your index fingers pull triggers that shoot guns and perform other functions. The controllers for the upcoming Xbox 360 and Playstation 3 consoles appear to offer more of the same.
There are two ways to look at the similarity between these controllers. Are they are identical because the design has been honed to perfection and there is no room for improvement? That is what happened, for example, with the car steering wheel. All cars have steering wheels, and they have all had steering wheels for nearly a century.
The other approach is think about controllers in a completely different way -- a way that can revolutionize gameplay.
Nintendo took the latter approach: Its designers got outside of the box and innovated. When you first see the new Revolution controller, it appears a little ridiculous. It looks like the remote control for a TV and it has no joystick. But the initial reviews have been good, and it actually makes sense once you understand the design principles.
The key to this very different controller is on the inside...
Gyroscopes to the RescueThe key to Nintendo's new game interface lies inside the controller. Instead of using a joystick to control the game, the primary control is the controller itself. The controller contains solid-state accelerometers and gyroscopes that let it sense:
Tilting and rotation up and down
Tilting and rotation left and right
Rotation along the main axis (as with a screwdriver)
Acceleration up and down
Acceleration left and right
Acceleration toward the screen and away The surprising thing is that you can create an accurate and natural user interface this way.
Photo courtesy Nintendo of America, IncThe controller from all angles
At this early stage, Nintendo has several demos that let people experience the new controller. In one demo players shoot at an object on the screen. You simply point the controller at the target and fire. It is completely natural. In another demo you fly an airplane. You simply move the controller in the way you want the plane to move, and the plane on the screen moves. It is easy to do sharp turns, barrel rolls and loops.
In other demos the controller acts like a stick. The controller manipulates an on-screen fishing pole, an on-screen drum stick or an on-screen fly swatter.
Photo courtesyNintendo of America, IncThe controller in actionThere are at least four advantages to this approach:
Controller use seems to be completely intuitive, meaning that anyone can use it almost immediately -- there's no learning curve or fumbling as with joysticks.
The controller is very fast. You can move from one side of the screen to the other with a quick flick of the wrist.
The controller is very accurate: Things respond exactly as you expect.
The controller lends itself naturally to new game-playing paradigms. Playing a sword-fighting or fishing game with a joystick is clunky. Playing it with a controller that can be swung like a sword or a fishing pole is completely natural.
In the next section we'll discuss some variations on this controller.
VariationsThe system is not quite as pure as the previous description would lead you to believe: In many games you need the ability to aim and control more than one thing at a time. For example, in any first-person-shooter game, you will want to shot while running. This means that you must be able to aim the gun and simultaneously move your character. The Nintendo Revolution system has two ways to handle this problem.
Photo courtesy Nintendo of America, IncController with attached "nunchuk-style" analog unit
The preferred way is to attach a separate joystick pod to the controller. You hold the controller in one hand and the joystick in the other. In a first-person shooter game, the controller controls the gun and the joystick controls the running. The second possibility is to add a standard game controller. These add-ons attach to the controller using a special socket built into the butt of the controller. You can see a projection of what this may look like here.
Powering the Console
Rumored Features
The ability to play DVD movies
The ability to connect to the Internet using a Cat-5 cable or a WiFi connection
The controller will connect to the console wirelessly using Bluetooth
The console will connect to both TVs and computer monitors Although the internals of the console are still up in the air, enough information has been announced or inferred to build a fairly accurate view of what the Nintendo console will probably have inside.
Nintendo has taken an interesting approach. Instead of trying to compete with the multi-core chips in the Xbox 360 and the PS3, Nintendo is instead focusing on building a console that is "more power-efficient, quieter and faster to start" [ref]. Nintendo is going on the assumption that you don't necessarily need the biggest, fastest processor to create engaging games.
Nintendo will be using what appears to be a regular 2.5 GHz PowerPC chip as the CPU. The chip is made by IBM and will have 512MB of RAM on board. The main benefit of this approach is that it will make game development easy. Programmers are quite familiar with the software development process on a "normal" CPU. In contrast, many developers have stated that development on the 6-core or 7-core CPUs in the Xbox 360 and PS3 will be quite challenging.

The graphics processor will use an ATI chipset running at 600Mhz and connected to 256 MB of RAM. It will also have 32 shader pipelines -- 16 fewer than the Xbox 360. However, the Nintendo GPU is rumored to run at 500 million triangles per second (100 million sustained) -- roughly equivalent to the Xbox 360. It will also be able to handle 50 billion shader operations per second, which is about the same as the 360 as well.
The Nintendo console is also rumored to have a PPU -- a physics processing unit. This would be a first in the console wars. A PPU is a custom processor for handling physics calculations (in the same way that the GPU is a custom processor for handling graphics calculations). Physics calculations include things like collision detection and the modeling of complex objects like moving hair and clothes. Having a PPU would offload all of these calculations from the CPU.
If Nintendo pulls it off, the Revolution console will have all the firepower of Xbox 360 and much simpler architecture that makes life easier for software developers.
The system is set to launch sometime in the first half of 2006 with a projected price point of $199 or less.
Next we'll see how the Revolution will stack up to its predecessor, the Nintendo GameCube.
GameCube vs. RevolutionThe Nintendo GameCube was released in September of 2001. The Revolution will come out about four years later. It is interesting to compare the two systems and see just how much can change in 48 months:
Nintendo of America, Inc
The GameCube has a single-threaded PowerPC processor running at 485 MHZ. The Revolution's dual-threaded processor running at 2.5 GHZ should be at least 10 times faster.
The GameCube has 24 MB of RAM. The Revolution will have about 20 times more RAM with 512 MB.
The video card in the GameCube has 16 MB of video RAM, while the Revolution has 256 MB, or 16 times more.
The graphics card in the GameCube runs at 162 MHZ. In the Revolution it runs at 600 MHZ, about four times faster.
The GameCube is able to paint about 20 million polygons per second. The Revolution will be able to create over 100 million per second and they will be realistically shaded.
Unlike the GameCube, the Revolution will be able to play DVDs.
The Revolution will also using completely redesigned wireless game controller.
For more information about the Nintendo Revolution and related topics, check out the links on the next page.
Lots More Information
Related HowStuffWorks Articles
How GameCube Works
How Nintendo64 Works
How Nintendo DS Works
How Playstation 3 Works
How Playstation 2 Works
How PSP Works
How Xbox 360 Works
How Xbox Works
How Bluetooth Works
How Microprocessors Work
How Graphics Cards Work
How RAM Works
More Great Links

Nintendo
IGN's Nintendo Revolution FAQ
Nintendo Controller Trailer
Gyration's Patented Technologies