Crossover

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Posted by r2d2 03/19/2009 @ 05:12

Tags : crossover, movies, cinema, entertainment

News headlines
Report: New Buick Crossover to Get gm's Plug-In Hybrid Two Mode ... - MotorTrend Magazine
But now, an as-yet-unnamed Buick crossover (pictured) -- teased recently in a CBS news report by GM design director Ed Welburn -- has reportedly emerged as the front runner, according to GM-Volt's sources. The new Buick is said to be based on the same...
Lexus RX crossover awarded IIHS Top Safety Pick - Motor Authority
Anyone in the market for the new 2010 Lexus RX can rest assure they are buying one of the safest crossovers available as the vehicle has just earned the highest safety rating from the Insurance Institute for Highway Safety (IIHS)....
A new conference is born - Aurora Beacon News
Four crossover contests, which will not count toward the conference record, will also be included. Those will be played on weekend dates if possible because of longer travel. Football teams will play their division rivals and also play two crossover...
Feed The Children, North America Mission Board, Crossover ... - Earthtimes (press release)
(Business Wire) Feed The Children will deliver three truckloads of food and personal care items to area churches in conjunction with the Southern Baptist Convention and Crossover Louisville events. This truck distribution is made possible by the North...
2009 Jeep Patriot Limited Long-Term Report 1 of 4 - Four Wheeler
Yes, it's a crossover, and yes, it has no low-range, and it even has four-wheel independent suspension. It is also, however, a Jeep, and it is Trail Rated. It has also been a bright light in an otherwise dark time for Chrysler, having been the...
Steering: Saginaw steering box, Sky High Steer crossover steering ... - 4Wheel and Off Road Magazine
A trussed and shaved 14-bolt rear axle complements the front beef. It also contains 5.38 gears and is assisted by a Detroit Locker. Stopping power has been upgraded with a Sky Manufacturing disc brake conversion, and a homebrew traction bar was fitted...
Demand is strong for Europe's small luxury crossovers - Automotive News
European makes can't get enough of the small luxury crossovers they introduced this year. The Audi Q5, Mercedes-Benz GLK and Volvo XC60 are bright spots for the three brands, whose US sales overall have suffered in the recession....
Some Warner Backers In Va GOP Endorse McDonnell - WJZ
With wide crossover appeal last year and a strong tail wind from Barack Obama's presidential bid, Warner won 65 percent of the vote over Republican former Gov. Jim Gilmore. Monday's endorsements indicate that crossover appeal won't be so easy for...
Crossover Medical Technology Inc. Philadelphia PA: 100 seater to ... - PressReleasePoint (press release)
Pune – June 16, 2009 - Crossover Software Technology Pvt. Ltd., www.crossoverint.com, one of the premier service providers in the healthcare sector today announced the expansion of its Pune, India unit. Crossover plans to add 100 more seats to its...
Highbrows pan pop/classical crossover - Windsor Star
Such imprecise terms as "light classical," "classical light" and "crossover" increasingly blur any hard lines between high classical and pop. Schmaltz-waltz maestro Rieu hits his target dead-on with polished, if saccharine, performances....

CrossOver

Preview screenshot of CrossOver Mac running Microsoft Project 2003

CrossOver, known before version 6.0 as CrossOver Office, is the collective name for four commercial and proprietary programs developed by CodeWeavers that allow many Windows-based applications to run on Linux, Mac OS X and Solaris using a compatibility layer. The programs include CrossOver Mac, CrossOver Linux, CrossOver Games Mac, and CrossOver Games Linux.

The programs are modified, proprietary versions of the public Wine source tree with various compatibility patches added, more user-friendly configuration tools and commercial support. CodeWeavers employs several Wine developers and contributes code back to the free software/open source software Wine project as per the GNU LGPL, although CrossOver is proprietary software.

In June 2005, CodeWeavers announced a new Apple Mac OS X version of CrossOver Office called CrossOver Mac that will support Windows-to-Mac application porting on Intel-based Macs. Crossover Mac was released on January 10, 2007. With the release of Crossover Mac 7 on June 17, 2008, Crossover Mac was divided into Standard and Pro versions like Crossover Linux. The standard version includes six months of support and upgrades, while the Pro version includes one year of support and upgrades and a free copy of Crossover Games.

The program aims to integrate properly with GNOME and KDE so that applications will run seamlessly in the Linux environment.

CrossOver Linux is offered in two versions — Standard and Professional. CrossOver Linux Professional provides enhanced deployment and management features for corporate users. The Standard version allows a single user of a single machine. The Professional version allows multiple users.

CrossOver Server allows Windows applications to run in a distributed thin-client environment under Linux and Solaris. CrossOver Server was discontinued in 2007 as many of its features now appear in CrossOver Linux Professional.

CrossOver Games, announced on 10 March 2008, is a new product that lets the users play a broad range of games, "particularly games with a lot of replayability such as MMOs like World of Warcraft and the range of games from Valve e.g., Team Fortress 2, Counter-Strike: Source, and so on". The difference with regular CrossOver is that CrossOver Games will have a shorter release cycle in order to update faster to the latest work on Wine than with regular CrossOver, which targets stability and reliability.

A full list is available from CodeWeavers’ website.

CodeWeavers has also designed an interest gauging system on their Web site where one can donate money towards a particular application in order to encourage the development team to focus their attention on it and make it fully compatible.

On October 28, 2008 as the result of the Lame Duck challenge, Codeweavers gave all of their products away free. Codeweavers' main page was temporarily replaced due to the day's unusually high traffic. According to a CodeWeavers blog entry at least 650,000 product registrations had been given away during October 28.

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Fictional crossover

A fictional crossover is the placement of two or more otherwise discrete fictional characters, settings, or universes into the context of a single story. They can arise from legal agreements between the relevant copyright holders, or because of unauthorized efforts by fans.

Crossovers happen in various media mostly because of some intent by the property rights holders to reap the financial reward of combining two or more popular, established properties. In other cases, the crossover can serve to introduce a new concept that derives from an older one.

Crossovers generally occur between properties owned by a single holder, but they can more rarely involve properties from different holders, provided that the inherent legal obstacles can be overcome. They may also involve using characters that have passed into the public domain with those that currently enjoy copyright protection.

A crossover story may try to explain its own reason for the crossover, such as "they live next door" (one example being the casts from Golden Girls and Empty Nest) or "a dimensional rift brought them together" (a common explanation for science fiction properties that have different owners). Some crossovers are not explained at all. Others are absurd or simply impossible within the fictional setting, and have to be ignored by the series' respective continuities. Still others intentionally make the relations between two or more fictional universes confusing, as with The Simpsons and Futurama, where each show is fiction in the other.

Crossovers of multiple characters owned by one company or published by one publisher, have been used to set an established continuity, where characters can frequently meet within one setting. This is especially true of comic book publishers, as different characters in various Marvel, DC or Valiant comic books frequently interact with one another since they live in the same "universe." For example, in the Marvel Comics universe, the X-Men have frequent dealings with another group of Marvel heroes, the Fantastic Four, just as in the DC Comics Universe, Batman and Superman frequently collaborate. In comic book terminology, these "guest star" roles are common enough that they are not considered crossovers. A crossover in comic book terms only occurs when a story spans more than one title. This has led to "crossover events", in which major occurrences are shown as affecting (almost) all the stories in the shared universe.

The first major crossover event was spearheaded by, then Marvel Editor-in-Chief, Jim Shooter. As a way to further toy sales he devised the Secret Wars crossover which brought all the major Marvel heroes into a twelve issue mini-series to battle a common threat. After the threat was dealt with they all returned to their regular titles. This Secret Wars was hailed as both a critical and commercial success largely because the events of the crossover had lasting effects on the characters (such as the introduction of Spider-Man's black suit which would later become the villain Venom). Jim Shooter later perfected his crossover at Valiant Comics with the Unity event. Unity brought all the Valiant characters together to defeat Mothergod but was told within the existing Valiant Comics titles (and two bookend special issues). Readers were not obliged to buy all 18 chapters as the story was coherent when reading just one title, but far more layered when all were read. Like Secret Wars, the Unity crossover had lasting effects on the Valiant universe most notably the introduction of Turok, the birth of Magnus Robot Fighter and the death of a major Valiant hero.

The Aliens Versus Predator franchise was a success that continued into many games and two movies and even an Aliens Versus Predator Versus The Terminator.

Cartoon crossovers aren't terribly uncommon, and most of them - like comics or live-action TV shows - will often feature characters owned by the same company or network. One example is Cartoon Network's The Grim Adventures of the Kids Next Door. It features 5 crossovers - Ed, Edd n Eddy, Codename: Kids Next Door, The Grim Adventures of Billy and Mandy, The Powerpuff Girls, and one phrase of Scooby-Doo, which are all licensed Cartoon Network series. Most of the last episodes of the Lilo & Stitch: The Series (a spinoff of the movie of the same name) had crossovers with various other Disney cartoons, including The Proud Family, Kim Possible, Recess and American Dragon Jake Long, although one might count them as mere cameos, as each plotline took place exclusively in Lilo's hometown in Hawaii. The Jimmy Timmy Power Hour trilogy is another example, as Jimmy Neutron and Timmy Turner switch universes. Another crossover is The Rugrats Go Wild when the Rugrats are stranded on an island where The Wild Thornberrys were at the time.

However, not all crossovers are necessarily composed of characters under common ownership. Two of the most notable cartoon crossovers consisted of characters from different companies. Disney's famous movie Who Framed Roger Rabbit, a landmark in animation, had characters from various companies, most notably Disney and Warner Bros. Daffy Duck and Donald Duck made a simultaneous appearance in one scene, in which the two of them exchanged blows during a piano duet. Later in the movie, Mickey Mouse and Bugs Bunny were shown parachuting together (to keep things from getting too iffy legally, Mickey and Bugs' lines were written so that each of them said the exact same number of words in the movie). And of course, the end of the movie features all the cartoons from all of the animation companies joining together in song, to be concluded by Porky Pig uttering (or, rather, stuttering) his famous "That's All, Folks!" line as Tinker Bell ends the scene with a magical fade-out.

Another cartoon crossover would occur in 1990, Cartoon All-Stars to the Rescue. This cartoon featured popular characters from children's Saturday morning cartoons, banding together to preach an anti-drug message. ABC, CBS, Fox, and NBC aired this half-hour special one Saturday morning with characters from all their networks, including Huey, Dewey, and Louie (from DuckTales), Winnie the Pooh, Tigger, Slimer (from The Real Ghostbusters), Michelangelo (from Teenage Mutant Ninja Turtles), Bugs Bunny, Daffy Duck, Alvin and the Chipmunks, The Smurfs, ALF (from his short-lived cartoon spinoff), Garfield, and the trio of Baby Kermit, Baby Piggy, and Baby Gonzo (from Muppet Babies). Animation companies granted unlimited, royalty-free use of their cartoon characters for this project, a feat that has been unequalled before or since then. This cartoon was also introduced by then-President George H. W. Bush and Barbara Bush, and would be distributed to schools and video stores free of charge nationwide.

The King of Fighters, Marvel vs. Capcom, and many other franchises from third-party developers such as Capcom and SNK bring these licenses together. The 2.5D fighting game series, Super Smash Bros., brings Nintendo characters together for a massive fight. The third game in the series, Super Smash Bros. Brawl introduces the first non-Nintendo characters with the inclusion of Solid Snake and Sonic the Hedgehog, of Konami's Metal Gear series and Sega's Sonic the Hedgehog series respectively. Namco x Capcom, however, is a fighting/RPG from Monolith Soft featuring characters from the Capcom and Namco universe. Also, the new creation from Koei, Warriors Orochi crosses characters from both the Samurai Warriors series and the Dynasty Warriors series. The Namco-developed Soul series, particularly Soulcalibur II and Soulcalibur IV feature characters from outside of Namco's titles (Link from Nintendo's The Legend of Zelda series, Heihachi from Tekken, and Todd McFarlane's Spawn) and the Star Wars universe respectively.

Mario & Sonic at the Olympic Games was the first time that Mario and Sonic appeared in a game together.

In the RPG field, Kingdom Hearts mixes Disney and Final Fantasy characters together. Also, Crash Bandicoot and Spyro the Dragon join forces in Crash Bandicoot Purple: Ripto's Rampage and Spyro Orange: The Cortex Conspiracy.

In 1993 a video game was released based on the Robocop vs. Terminator comic book, whilst the Super Nintendo version used the style of the comic, the Sega Genesis/Megadrive version utilized a style more closer to that of the respective movies.

Super Robot Wars are turn-based strategy games featuring a variety of Japanese mecha series from many generations, such as Mazinger Z, Gundam, Neon Genesis Evangelion, and GaoGaiGar. Wario Blast: Featuring Bomberman! features Wario of Nintendo fame, and Bomberman of Hudson fame, battling against each other. Nicktoons Unite! is a video game similar to the Jimmy Timmy Power Hour, but the shows SpongeBob SquarePants and Danny Phantom are included in the crossover. There is also Mortal Kombat vs. DC Universe, which features many famous characters from both sides like Liu Kang and Sub-Zero for the Mortal Kombat side, and characters like Batman and Superman for the DC side. The story explains the merging of the two worlds and the struggle from both sides to overcome the other one: howewer the game is not considered canon for both companies.

In literature, certain authors also engage in crossovers by including characters from different novels they have written in one particular volume; Michael Moorcock frequently uses this device - particularly in his Eternal Champion sequence of novels, which establish a vast 'multiverse' populated by numerous different characters, many of whom appear in different novels and even different genres. Kim Newman is another author who frequently uses this device. The works of James Branch Cabell, William Faulkner, Margaret Laurence, Mordecai Richler, Edgar Rice Burroughs and Isaac Asimov also 'crossover' with each other, linking different characters and settings together over a number of different works. Brazilian writer Monteiro Lobato also created solid and imaginative crossovers, using elements and characters from Brazilian folklore such as the Cuca and Saci, from Greek Mythology such as Heracles, from the Arabian Nights, from Fairy Tales such as Grimm's Snow White, western literature such as Peter Pan, silent movies such as Popeye and Felix the Cat (cartoons) and western films actor Tom Mix.

Other examples include many characters from seemingly unrelated works, which are set into a fictional reality of an actual location. Two examples include Irvine Welsh and Bret Eaton Ellis, whose main characters in their most noted works, American Psycho (Ellis),and Trainspotting (Welsh) appear in several other works. One is noted in the film 'Rules of Attraction' when Sean Bateman answers the phone and askes "Patrick?" who in Ellis' universe is Patrick Bateman, protagonist of 'American Psycho'. Sean is in that book but not in the movie. Another book, A Night In Lonesome October cross-overs Sherlock Holmes, Doctor Frankenstein, Jack the Ripper and the Cthulhu Mythos, adding Familiars and ancient magic to the mix.

It is also common for authors to 'crossover' characters who have passed into the public domain, and thus do not require copyright or royalty payments for their use into their works; a prominent example of this occurs in Loren D. Estleman's novel Sherlock Holmes vs. Dracula, in which Sherlock Holmes and Dracula are brought together and pitted against each other. The League of Extraordinary Gentlemen by Alan Moore and Kevin O'Neill is another example of this, as all of the main characters and most of the secondary / background characters are fictional characters whose copyright has expired, and all are characters of different authors and creators brought together within one massive extended universe. Many of the works of Philip José Farmer's Wold Newton family sequences (which has also been explored and developed by other authors) also utilize and interweave numerous otherwise unrelated fictional characters into a rich family history by speculating familial connections between them (such as a blood-relationship between Sherlock Holmes and Tarzan).

Occasionally, authors will include into crossovers classic fictional characters whose copyright is still held by the original authors (or at least their estates), but who are nevertheless considered iconic or 'mythic' enough to be recognised from a few character traits or descriptions without being directly named (thus not requiring royalties payments to be made to the copyright holder). A prominent example occurs within the first volume of The League of Extraordinary Gentlemen, wherein a character who is clearly intended in appearance and description by other characters to be Dr Fu Manchu appears as a significant villain; however, as this character was not in the public domain at the time of writing and the rights still held by the estate of his creator Sax Rohmer, he is not directly named as such in the work and is only referred to as 'the Devil Doctor'.

In its simplest and most common form, a television crossover involves a starring character on a parent show appearing on a spin-off because of established character relationships. An obvious example of this type of crossover occurred when Cliff Huxtable of The Cosby Show visited his daughter, Denise, on A Different World. Another example of this is the appearances made by Buffy the Vampire Slayer characters to Angel in Los Angeles from Sunnydale.

Sometimes, spin-off crossovers don't involve principals, but rather supporting cast members. For instance, the main link between Green Acres, Petticoat Junction and The Beverly Hillbillies is Sam Drucker.

Depending on the complexity of the franchise, though, the crossover can be even more indirect, serving to suggest the size of the fictional world. This sort of crossover is somewhat common to the Star Trek universe, where minor guest stars from one series have appeared as featured guest stars later on. A good example of this kind of crossover is that of Arne Darvin. Despite the passage of about a century of narrative time, he appeared as a secondary character in the episode "The Trouble with Tribbles", but was the principal villain of the Star Trek: Deep Space Nine episode, "Trials and Tribble-ations".

Star Trek affords an easy understanding of yet another kind of spin-off crossover: that of crossover by implication. By making the various ships and devices to be of roughly the same visual design, the implication is that all of series take place in the same universe. This kind of crossover occurs in other shows when shared characters are mentioned but do not actually appear, as when Michael Stivic was referenced on Gloria.

The distinction between "spin-off" and "crossover" is sometimes narrow. The two terms can become especially conflated if two shows are linked by a guest star with a single appearance. There is debate, for instance over whether Out of the Blue is a spin-off of Happy Days, or whether the star of Out of the Blue merely crossed over into Happy Days.

Crossovers involving principals can also occur when the characters have no prior relationship, but are related by time period, locale or profession. Such crossovers were characteristic of early Warner Bros. westerns. Perhaps the biggest such crossover was seen in the episode "Hadley's Hunters" from the fourth season of Maverick. It featured the lead characters of Cheyenne, Bronco, Lawman and Sugarfoot, along with signature props from Colt .45 and even the non-Warner's western, Wanted: Dead or Alive. While seeing so many crossovers in one episode is rare today, the Law and Order franchise rivals the old ABC/Warner's westerns in terms of frequency. Like them, the Law and Order series afford a commonality of setting which lends itself to crossovers.

Though most common on shows of the same production company, they have also occurred because shows share the same distributor or network. A good example of this kind of link is that between Murder She Wrote and Magnum, P.I.. Both these shows were made by different companies, but owned by Universal Studios and broadcast on CBS. A more unusual case is that of Mad About You and Friends, which are conjoined by the character of Ursula Buffay. Neither show shares any production or distribution commonality whatsoever, but, rather, an actress (Lisa Kudrow), a setting (New York City) and a schedule (Friends initially followed Mad About You on NBC's Thursday night schedule). Also, on The King of Queens, characters from Everybody Loves Raymond appear occasionally in cameos with Doug and the rest of the cast.

Mad About You and Friends share another type of "network crossover." On rare occasions, networks have chosen to theme an entire night's programming around a crossover event. In their case, a New York City blackout caused by Paul Reiser's character on Mad About You was experienced by the characters on Friends and Madman of the People. But event nights can also be linked by a single character's quest across multiple shows on the same evening. ABC attempted this kind of "event night" crossover with its Friday night programming during the 1997 season. There, they proposed that the titular character of Sabrina the Teenage Witch should chase her cat, Salem, through Boy Meets World, You Wish and Teen Angel because it had run away with a "time ball" that was displacing each show through time. Another ABC crossover was featured on a Saturday morning cartoon-- it featured none of the characters from any of the 1 Saturday Morning shows, but a common "villain" named S.T.U.A.R.T. appeared on Doug, Recess and Pepper Ann. Sometimes the crossovers between adjoining shows can be even more subtle than these examples, such as when characters at the end of an episode of Spin City decided to watch a broadcast of the fictional sports telecast, Sports Night, which led immediately into an episode of the sitcom of the same name.

Crossovers can take the form of a promotional cameo appearance, used to draw attention to another work of fiction, with little rational explanation in the context of the hosting show's narrative. When not clearly presented as parody, this is frequently scorned by fans as blatant commercialism. A notable example of this is The Simpsons episode A Star Is Burns, in which the character of Jay Sherman (from The Critic) appeared. This episode was largely condemned by fans of The Simpsons as existing to promote The Critic. Even Simpsons creator Matt Groening objected, preferring to remove his name from the credits of that particular episode in protest.

Often, the problems of bringing together two shows with different narrative ambitions makes the writing of a crossover burdensome. Such difficulties are encountered by situation comedies that wish to crossover with dramatic television programmes. The satirical crossover—ranging in length from a cameo to a full comedy sketch or episode—is an extremely popular way of circumventing this problem. By various means, such crossovers typically avoid outcry from fans by being obvious parody or homage. However, on rare occasion, the humor of such crossovers can be used by one show make a narrative point by capitalizing on the audience's experience of the other programme.

Such tongue-in-cheek crossovers typically fall into one of several broad categories.

Sometimes, crossovers occur even when there was no explicit intent to create them. Viewer interpretation can play into the size and complexity of crossovers. These sort of crossovers involve no creation of additional material, but merely result from inferences drawn about existing filmed episodes. Usually they are a product of narrative ambiguity. Perhaps the best example of this was caused by the unusual ending to St. Elsewhere. In that final episode, it was revealed that the entire run of the programme had been a figment of autistic character, Tommy Westphall. This lent itself to broad interpretation of the events of that series. Because the show had direct crossovers with twelve different programmes, and each one of these twelve had numerous other crossovers, linkages can be found from Elsewhere to 280 other shows, comprising what has been called "the Tommyverse".

In contrast with legal crossovers, unofficial crossovers are created solely because of the artistic pleasure derived by its producers. Generally, unofficial crossovers take the form of fan-written fiction and fan art, but it is increasingly prevalent in amateur films and audio. Whereas official crossovers are frequently stymied by such concerns as copyright, royalties payments, quality of writing and ownership of the characters, unofficial crossovers are unfettered by such concerns, so long as property holders do not exercise their right to enjoin the distribution of such material.

A good example would be the unauthorised live action fan film: Batman: Dead End, which brings together the properties of Batman, Alien and Predator in one setting.

The comedy music song and video "Ultimate Showdown of Ultimate Destiny" is like a giant crossover featuring many famous real and fictional characters battling in one giant showdown.

A fictional crossover is the placement of two or more otherwise discrete fictional characters, settings, or universes into the context of a single story. They can arise from legal agreements between the relevant copyright holders, or because of unauthorized efforts by fans. For example, many such works involving the Star Trek and Star Wars franchises exist throughout the Internet, with many dedicated websites and newgroups.

In the film I Am Legend, a billboard can be seen in Times Square depicting a crossover film of Batman and Superman, with a release date of May 15, 2010.

Unofficial crossovers can also occur in a "what-if" scenario. The most notable is an episode of Family Guy entitled "Lois Kills Stewie" which turned out to be a simulation along with the previous episode "Stewie Kills Lois". Stewie Griffin is confronted by Stan Smith and Avery Bullock from American Dad! while hacking into the central power grid at the CIA in a latest plan for world domination. Stewie mistakes Stan for Joe Swanson, due to notable similarities between the two shows. Stewie threatens to turn off all the electricity in the world until Stan and Bullock fulfill his demands of being "President of the World", which they do. Even though this never really happened (the entire episode was a virtual reality simulation run by Stewie), unlike the episodes "Meet the Quagmires" and "Blue Harvest", (which each had brief cameos by Roger the Alien) this is considered by some to mark the first official appearance of American Dad! characters in a Family Guy episode.

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Crossover study

A crossover trial also referred to as a crossover study is a clinical trial in which patients are given all of the medications to be studied, or one medication and a placebo in random order. These studies are generally done on patients with chronic diseases to control their symptoms. The data are analyzed according to the original intention to treat.

A crossover study has the advantage over a simple double-blind study that the variability between patients is minimized because each patient crossing over in effect serves as their own control. One disadvantage is that long term effects cannot be tracked with this approach. Another disadvantage is that curative therapies cannot be tested after one another or before a placebo.

There are some important issues with respect to the design of cross-over studies. Two in particular may often crop up.

First is the issue of order effects, because it is possible that the order in which treatments are administered may affect the outcome. An example might be a drug with many adverse effects given first, making patients taking a second, less harmful medicine, more sensitive to any adverse effect.

Second is the issue of carry-over between treatments. In practice carry-over can be and is often dealt with by the use of a wash-out period between treatments, or by making observations sufficiently later after the start of a treatment period that any carry-over effect is minimized.

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Ethernet crossover cable

Crossover cable suitable for use with 100BASE-T4 (please note : Gigabit crossover) Fast Ethernet

An Ethernet crossover cable is a type of Ethernet cable used to connect computing devices together directly where they would normally be connected via a network switch, hub or router, such as directly connecting two personal computers via their network adapters.

The 10BASE-T and 100BASE-TX Ethernet standards use one wire pair for transmission in each direction. The Tx+ line from each device connects to the tip conductor, and the Tx- line is connected to the ring. This requires that the transmit pair of each device be connected to the receive pair of the device on the other end. When a terminal device is connected to a switch or hub, this crossover is done internally in the switch or hub. A standard straight through cable is used for this purpose where each pin of the connector on one end is connected to the corresponding pin on the other connector.

One terminal device may be connected directly to another without the use of a switch or hub, but in that case the crossover must be done externally in the cable. Since 10BASE-T and 100BASE-TX use pairs 2 and 3, these two pairs must be swapped in the cable. This is a crossover cable. A crossover cable must also be used to connect two internally crossed devices (e.g., two hubs) as the internal crossovers cancel each other out. This can also be accomplished by using a straight through cable in series with a modular crossover adapter.

Because the only difference between the T568A and T568B pin/pair assignments are that pairs 2 and 3 are swapped, a crossover cable may be envisioned as a cable with one connector following T568A and the other T568B. Such a cable will work for 10BASE-T or 100BASE-TX. 1000BASE-T4 (Gigabit crossover), which uses all four pairs, requires the other two pairs (1 and 4) to be swapped and also requires the solid/striped within each of those two pairs to be swapped.

Certain equipment or installations, including those in which phone and/or power are mixed with data in the same cable, may require that the "non-data" pairs 1 and 4 (pins 4, 5, 7 and 8) remain un-crossed.

In practice, it does not matter if your Ethernet cables are wired as T568A or T568B, just so long as both ends follow the same wiring format. It is just as valid to make a four-pair crossover using T568A, or a two pair crossover using T568B, as it is to wire them the way shown here. Typical commercially available "pre-wired" cables can follow either format depending on who made them. What this means is that you may discover that one manufacturer's cables are wired one way and another's the other way, yet both are "correct" and will work. In either case, T568A or T568B, a normal (un-crossed) cable will have both ends wired according to the layout in the Connection 1 column.

Automatic MDI/MDI-X Configuration is specified as an optional feature in the 1000BASE-T standard, meaning that straight-through cables will usually work between Gigabit capable interfaces. This feature eliminates the need for crossover cables, making obsolete the uplink/normal ports and manual selector switches found on many older hubs and switches and greatly reducing installation errors. Note that although Automatic MDI/MDI-X is generally implemented, a crossover cable would still be required in the occasional situation that neither of the connected devices has the feature implemented and enabled.

Even for legacy 10/100 devices, many NICs, switches and hubs automatically apply an internal crossover when necessary. Besides the eventually agreed upon Automatic MDI/MDI-X, this feature may also be referred to by various vendor-specific terms including: Auto uplink and trade, Universal Cable Recognition and Auto Sensing.

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Source : Wikipedia