USB 1.1, USB 2.0, and USB 3.0

History

USB stands for Universal Serial Bus. USB is a plug-and-play interface used between computers and add-on devices (such as audio players, joysticks, keyboards, scanners, mass storage devices, and printers). With USB, a new device can be installed into your computer without having to add an adapter card, or even having to turn the computer off. USB CD-RW drives can be installed by simply plugging them into the computer at any time during operation. The USB peripheral bus standard was jointly developed by Compaq, IBM, DEC, Intel, Microsoft, NEC, and Northern Telecom (though it is in small-part based upon a similar Serial Interface was developed for Atari Home Computers in 1980). The first computers that began shipping with USB capability, began showing up in late 1996. Today, the technology is now openly available for all computer and device vendors. Currently, USB is available on over 90% of computers manufactured today.

Why USB?

The purpose for USB was to provide a universal interface that would eventually replace different types of peripheral interfaces (parallel ports, serial ports, PS/2, etc.), while maintaining wide compatibly with current and future Windows operating systems. Since late 1996, Windows operating systems have been equipped with USB drivers or special software designed to work with specific USB I/O devices complying with the USB 1.0 Standard. With the introduction of Windows 98, a newer USB 1.1 standard was, for the first time, completely integrated within the operating system. The newer USB 1.1 Standard provided for tighter integration with Microsoft’s Plug and Play standard (PnP), making installation of external devices and peripherals virtually hassle-free, while still maintaining backward-compatibility with existing USB 1.0 devices. USB has since been integrated into every Windows operating system, with the exception of Windows NT.  While we tend not to think much about this technology, it was not so long ago that almost every device involved complex installation processes, and unique adaptor cards.

USB Today

Today, most new computers and peripheral devices are equipped with USB capability. The USB 1.1 Standard’s integration into the Windows 98 operating system was the catalyst that allowed countless USB devices to be created and sold for use with personal computers. USB has slowly become the interface of choice for connecting such devices as keyboards, mice, scanners, printers, external hard drives, thumbprint scanners, and even thumbdrives! However, newer and more-bandwidth-demanding devices such as digital cameras and external mass storage devices began to demonstrate the limitations of the USB 1.1 Standard. In late 2001, the USB 2.0 Standard was introduced to bridge the performance gap between the USB 1.1 Standard and the demand of high-bandwidth devices, while still maintaining wide compatibility with the current USB 1.1 Standard.

USB 2.0 is over 40 times faster than USB 1.1, with data throughput speeds reaching up to 480Mbits/s. The chart below compares USB 2.0 performance with existing USB 1.1 performance, as well as other interface standards.

 Compatibility

If you have an older PC, you may very well have a USB 1.1 interface.  USB is backwards compatible (as long as the cable connector fits).  A 1.1 port means devices will work at 1.1 speeds, etc.

Newer USB Standards

SuperSpeed USB from the USB-IF
 As technology innovation marches forward, new kinds of devices, media formats, and large inexpensive storage are converging. They require significantly more bus bandwidth to maintain the interactive experience users have come to expect. In addition, user applications demand a higher performance connection between the PC and these increasingly sophisticated peripherals. USB 3.0 addresses this need by adding an even higher transfer rate to match these new usage and devices.

USB continues to be the answer to connectivity for PC, Consumer Electronics, and Mobile architectures. It is a fast, bidirectional, low-cost, dynamically attachable interface that is consistent with the requirements of the PC platforms of today and tomorrow.

SuperSpeed USB brings significant performance enhancements to the ubiquitous USB standard, while remaining compatible with the billions of USB enabled devices currently deployed in the market. SuperSpeed USB will deliver 10x the data transfer rate of Hi-Speed USB, as well as improved power efficiency. 

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  • SuperSpeed USB has a 5 Gbps signaling rate offering 10x performance increase over Hi-Speed USB.
  • SuperSpeed USB is a Sync-N-Go technology that minimizes user wait-time.
  • SuperSpeed USB will provide Optimized Power Efficiency.No device polling and lower active and idle power requirements.
  • SuperSpeed USB is backwards compatible with USB 2.0. Devices interoperate with USB 2.0 platforms. Hosts support USB 2.0 legacy devices.

Wireless USB from the USB-IF
With more than 2 billion legacy wired USB connections in the world today, USB is the de facto standard in the personal computing industry. Soon, these same, fast, interoperable connections will become available in the wireless world, with the introduction of Wireless USB from the USB-IF.  Wireless USB is the new wireless extension to USB that combines the speed and security of wired technology with the ease-of-use of wireless technology. Wireless connectivity has enabled a mobile lifestyle filled with conveniences for mobile computing users. Wireless USB will support robust high-speed wireless connectivity by utilizing the common WiMedia MB-OFDM Ultra-wideband (UWB) radio platform as developed by the WiMedia Alliance.

UWB technology offers a solution for high bandwidth, low cost, low power consumption, and physical size requirements of next-generation consumer electronic devices. 

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  • Wireless USB is the first high-speed wireless personal interconnect technology to meet the needs of multimedia consumer electronics, PC peripherals, and mobile devices.
  • Wireless USB will preserve the functionality of wired USB while also unwiring the cable connection and providing enhanced support for streaming media CE devices and peripherals.
  • Wireless USB performance is targeted at 480Mbps at 3 meters and 110Mbps at 10 meters.

USB On-The-Go and Embedded Host
Virtually every portable device now uses USB for PC connectivity. As these products increase in popularity, there is a growing need for them to communicate both with USB peripherals and directly with each other when a PC is not available.  There is also an increase in the number of other, non-PC hosts (Embedded Hosts) which support USB in order to connect to USB peripherals.

The newly published Revision 2.0 of the USB On-The-Go and Embedded Host Supplement addresses these scenarios by allowing portable devices and non-PC hosts to have the following enhancements: 

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  • Targeted host capability to communicate with selected other USB peripherals
  • Support for direct connections between OTG devices
  • A small USB connector to fit the mobile form factor
  • Power saving features to preserve battery life

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What is HDMI?

HDMI stands for High-Definition Multimedia Interface.  It is the first and only industry-supported, uncompressed, all-digital audio/video interface. By delivering crystal-clear, all-digital audio and video via a single cable, HDMI dramatically simplifies cabling and helps provide consumers with the highest-quality home theater experience. HDMI provides an interface between any audio/video source, such as a set-top box, DVD player, or A/V receiver and an audio and/or video monitor, such as a digital television (DTV), over a single cable.

HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It transmits all ATSC HDTV standards and supports 8-channel, 192kHz, uncompressed digital audio and all currently-available compressed formats (such as Dolby Digital and DTS), HDMI 1.3 adds additional support for new lossless digital audio formats Dolby TrueHD and DTS-HD Master Audio with bandwidth to spare to accommodate future enhancements and requirements.

The HDMI Connector

The Standard

HDMI is the de facto standard digital interface for HD and the consumer electronics market: More than 700 companies have become adopters, and nearly 200 million devices featuring HDMI are expected to ship in 2008, with an installed based of nearly one billion HDMI devices by 2010 (conservative estimates by In-Stat).

HDMI is the interface for convergence of PC and consumer electronics devices: HDMI enables PCs to deliver premium media content including high definition movies and multi-channel audio formats. HDMI is the only interface enabling connections to both HDTVs and digital PC monitors implementing the DVI and HDMI standards.

HDMI is continually evolving to meet the needs of the market: Products implementing new versions of the HDMI specification will continue to be fully backward compatible with earlier HDMI products.

The Market Adopts HDMI

HDMI has become so successful, so quickly, because it meets the needs of all facets of the Consumer Electronics and PC ecosystem. Manufacturers now have an all digital pipeline from the source material to the display; content providers have an interface that protects their intellectual property; and consumers have and easy-to-use, high quality, plug-and-play interface for their home entertainment environment.

HDMI Benefits

Quality: HDMI maintains the audio in its pure digital form all the way to the amplifier. Analog audio connections are more prone to losses depending on the cabling and other electronics of the audio rendering device. Compared to SPDIF connections, HDMI has significantly more bandwidth, allowing it to support the latest lossless audio formats such as Dolby TrueHD and DTS-HS Master Audio. These formats can not be supported over SPDIF connections due to their very high data rate requirements that exceed the capabilities of SPDIF. Please also see section on HDMI 1.3 for further details on Dolby TrueHD and DTS-HD Master Audio formats.

Ease of Use: HDMI combines video and multi-channel audio into a single cable, eliminating the cost, complexity, and confusion of multiple cables currently used in A/V systems. This is particularly beneficial when equipment is being upgraded or added.

Intelligence: HDMI supports two-way communication between the audio source (such as a DVD player) and the audio rendering device (such as an A/V receiver), enabling new functionality such as automatic configuration and one-touch play. By using HDMI, devices automatically deliver the most effective format (e.g. Dolby Digital vs. 2-channel PCM) for the A/V receiver that it is connected to – eliminating the need for the consumer to scroll through all the audio format options to guess what is best and properly supported.

A New Interface

With the advent of high-definition content, analog interfaces were becoming increasingly limited in their ability to deliver the highest quality, high-definition content.

HDMI has no conversion or compression of signals:

With the delivery of 1080p content, analog interfaces are nearing the end of their ability to deliver high-definition content without highly compressing the signal, which can result in loss of data and signal quality. HDMI has the bandwidth to send uncompressed video so there is no loss of data or signal quality

Content Protection allows access to HD content:

Content providers, including all the major movie studios, have been clear that much of the studio content will not be released in high-definition over unprotected analog interfaces. They have designated HDMI and/or DVI as the only interfaces that will be allowed to carry this new HD content.

HDMI Digital allows two-way communication:

HDMI supports two-way communication between the video source (such as a DVD player) and the DTV, enabling new functionality such as automatic configuration and one-touch play. By using HDMI, devices automatically deliver the most effective format (e.g. 480p vs. 720p, 16:9 vs. 4:3) for the display that it is connected to – eliminating the need for the consumer to scroll through all the format options to guess what looks best.

HDMI & Entertainment Systems

The most tangible and immediate way that HDMI changes the way we interface with our components is in the set-up. One cable replaces up to 11 analog cables, highly simplifying the setting up of a home theater as well as supporting the aesthetics of new component design with cable simplification.

Typical DVD Player With HDMI Out

Next, when the consumer turns on the HDMI-connected system, the video is of higher quality since the signal has been neither compressed nor converted from digital to analog and back.

Lastly, because of the two-way communication capabilities of HDMI, components that are connected via HDMI constantly talk to each other in the background, exchanging key profile information so that content is sent in the best format without the user having to scroll through set-up menus. The HDMI specification also includes the option for manufacturers to include CEC functionality (Consumer Electronics Control), a set of commands that utilizes HDMI’s two-way communication to allow for single remote control of any CEC-enabled devices connected with HDMI. For example, CEC includes one-touch play, so that one touch of play on the DVD will trigger the necessary commands over HDMI for the entire system to power on and auto-configure itself to respond to the command. CEC has a variety of common commands as part of its command set, and manufacturers who implement CEC must do so in a way that ensures that these common command sets interoperate amongst all devices, regardless of manufacturer.

CEC is an optional feature, however, so consumer interested in this functionality must look for CEC in the product feature list. Also, it is important to know that some manufacturers are creating their own proprietary names for their implementation of the CEC command set.

Typical Large Screen TV With HDMI Connectors

HDMI Tips

How many inputs/outputs do you need?

More and more inputs and outputs on components are appearing as more and more people are connecting with HDMI. It is common to see 3 and 4 inputs on an HDTV – many with one input on the side or front for connecting to game consoles or other portable devices such as digital still cameras or camcorders. Always think about the number of sources and displays (or projectors) that could become part of your home theater system, and make sure the device you are evaluating has the number of inputs and outputs to support your needs over the near and long term.

For those who have existing systems with one or two inputs, and are finding they need more, there are HDMI switches in the market that switch from multiple inputs (sources) to one output (to your display).

Think features rather than HDMI version number. 

HDMI is constantly evolving to meet the needs of the marketplace. The standard is constantly adding more and more features that manufacturers can implement if they desire. But HDMI does not require manufacturers to implement everything that HDMI can do. HDMI provides a menu of capabilities and allows the manufacturer to choose which of those features make sense for its product line.

As a result, it is recommended that consumers look for products with the features they want, rather than the version number of the HDMI components. Version numbers reflect capabilities, but do not correspond to product features. For example, if you want the new video features called Deep Color, look for Deep Color in the feature set rather than HDMI 1.3, the version of the specification that enabled Deep Color. Why? Because the version of the specification that enables Deep Color (1.3) does not mandate that Deep Color functionality be implemented.

However, it is important to also note that all HDMI versions are backwards compatible, so not matter what version of HDMI is in the component, all HDMI-enabled components will work together at the highest level of shared functionality.

Convergence Between The PC And Consumer Electronics

HDMI was developed using the same technology as DVI (Digital Visual Interface), the digital connection standard for the PC environment. So, HDMI is fully compatible with all DVI-enabled PCs (since HDMI offers both audio and video over one cable, and DVI carried only video, DVI-HDMI connectivity requires a separate audio cable).

HDMI enables PCs to deliver premium media content including high definition movies and multi-channel audio formats. HDMI is the only interface enabling connections to both HDTVs and digital PC monitors implementing the DVI and HDMI standards – fully compatible with the hundreds of millions of DVI displays already in the market.

HDMI Cables

What is the difference between a “Standard” HDMI cable and a “High-Speed” HDMI cable?

Recently, the HDMI standards body announced that cables would be tested as Standard or High-Speed cables.

• Standard (or “category 1”) cables have been tested to perform at speeds of 75Mhz, which is the equivalent of a 1080i signal.
• High Speed (or “category 2”) cables have been tested to perform at speeds of 340Mhz, which is the highest bandwidth currently available over an HDMI cable and can successfully handle 1080p signals including those at increased color depths and/or increased refresh rates. High-Speed cables are also able to accommodate higher resolution displays, such as WQXGA cinema monitors (resolution of 2560 x 1600).

Does HDMI accommodate long cable lengths?

HDMI technology has been designed to use standard copper cable construction at long lengths. In order to allow cable manufacturers to improve their products through the use of new technologies, HDMI specifies the required performance of a cable but does not specify a maximum cable length. We have seen cables pass “Standard Cable” HDMI compliance testing at lengths of up to a maximum of 10 meters without the use of a repeater. It is not only the cable that factors into how long a cable can successfully carry an HDMI signal, the receiver chip inside the TV or projector also plays a major factor. Receiver chips that include a feature called “cable equalization” are able to compensate for weaker signals thereby extending the potential length of any cable that is used with that device.

With any long run of an HDMI cable, quality manufactured cables can play a significant role in successfully running HDMI over such longer distances.

HDMI FAQs

Q. How can I tell the differences in each version of the HDMI specification?

Download a copy of the most recent specification of HDMI. At the beginning of the document, there is a section called “Revision History.” In this section, you can view all of the the changes for each revision of the Specification.

Q. Are all of the new HDMI versions backward compatible with previous versions?

Yes, all HDMI versions are fully backward compatible with all previous versions.

Q. What’s new in the HDMI 1.3 Specification?

• Higher speed: Although all previous versions of HDMI have had more than enough bandwidth to support all current HDTV formats, including full, uncompressed 1080p signals, HDMI 1.3 increases its single-link bandwidth to 340 MHz (10.2 Gbps) to support the demands of future HD display devices, such as higher resolutions, Deep Color and high frame rates. In addition, built into the HDMI 1.3 specification is the technical foundation that will let future versions of HDMI reach significantly higher speeds.
• Deep Color: HDMI 1.3 supports 10-bit, 12-bit and 16-bit (RGB or YCbCr) color depths, up from the 8-bit depths in previous versions of the HDMI specification, for stunning rendering of over one billion colors in unprecedented detail.
• Broader color space: HDMI 1.3 adds support for “x.v.Color™” (which is the consumer name describing the IEC 61966-2-4 xvYCC color standard), which removes current color space limitations and enables the display of any color viewable by the human eye.
• New mini connector: With small portable devices such as HD camcorders and still cameras demanding seamless connectivity to HDTVs, HDMI 1.3 offers a new, smaller form factor connector option.
• Lip Sync: Because consumer electronics devices are using increasingly complex digital signal processing to enhance the clarity and detail of the content, synchronization of video and audio in user devices has become a greater challenge and could potentially require complex end-user adjustments. HDMI 1.3 incorporates automatic audio synching capabilities that allows devices to perform this synchronization automatically with total accuracy.
• New HD lossless audio formats: In addition to HDMI’s current ability to support high-bandwidth uncompressed digital audio and all currently-available compressed formats (such as Dolby® Digital and DTS®), HDMI 1.3 adds additional support for new lossless compressed digital audio formats Dolby TrueHD and DTS-HD Master Audio™.

Q. What is the difference between DVI and HDMI?

HDMI is DVI with the addition of:

• Audio (up to 8-channels uncompressed)
• Smaller Connector
• Support for YUV Color Space
• CEC (Consumer Electronics Control)
• CEA-861B InfoFrames

Q. Is HDMI backward compatible with DVI (Digital Visual Interface)?

Yes, HDMI is fully backward compatible with DVI compliant devices. HDMI DTVs will display video received from existing DVI-equipped products, and DVI-equipped TVs will display video from HDMI sources. However, some older PCs with DVI are designed only to support computer monitors, not televisions. Consumers buying a PC with DVI should make sure that it specifically includes support for television formats and not just computer monitors.

Also, consumers may want to confirm that the DVI interface supports High-bandwidth Digital Content Protection (HDCP), as content that requires HDCP copy protection will require that both the HDMI and DVI devices support HDCP to properly view the video content.
Source: HDMI.org

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The cable selection at the electronics store could be renamed the “wall of confusion.” Not only are there dozens of different kinds of audio/video cable — some for stereos, some for home theaters, some for HDTVs and some for … who the heck knows? Even if you’re lucky enough to find the cable you need, you still have to decide between super expensive and suspiciously cheap.

And then there’s the salesman. “Have you heard of silver-plated connectors?” What? “If you’re buying speaker wire, then you should also buy these stands that keep the wire from touching the floor.” Why? “The more expensive the cable, the better the sound.” Really?

In this article, we’re going to give it to you straight. We’ll explain, in simple terms, what each type of audio/video cable does and where it should be used. Along the way, we’ll debunk some cable myths, starting with the idea that the most expensive cable is the best.

What is cable?

The role of cable is to carry an audio or video signal from one device to another. Cables carry signals between DVD players and TVs, stereo receivers and speakers, and computers and video projectors. Cables don’t change the nature of the audio or video signal they carry. They don’t convert or process signals in any way. That’s the job of the devices on either end. The cable itself is just the messenger.

Cables are made up of three basic parts: conductor, shielding and connector [source: Graves]. The conductor is the wire that actually carries the signal. One or more layers of shielding prevent the wire from acting as an antenna that picks up radio frequency interference (RFI) and electromagnetic interference (EMI) [source: Graves]. The connector is the plug at the end of the cable that connects to your device.

Cables are important components of any home stereo or home theater setup. If you don’t use the right cables for the right job then you could end up with subpar sound or picture quality. And if you use cables that are damaged or otherwise junky, you could really end up with a lousy experience. For audiophiles, using low-end cables with a $5,000 plasma HDTV is like putting crappy tires on a Ferrari.­

Some audio/video experts argue that consumers should spend 20 percent of their total system cost on cables alone [source: Rushing]. The truth is that many cheaper cables offer a listening/viewing experience that most consumers could never tell from the really high-end cables [source: Rothman].

To keep things simple, we’re going to break down the overwhelming amount of cable types into three categories: audio-only, video-only and audio/video cables that carry both sound and picture.

Audio Cables

Let’s start with audio-only cables. The most common audio cables are called analog RCA cables. These are the cables with red and white, or sometimes red and black connectors. RCA cables are widely used to connect devices like VCRs and DVD players to TV sets or CD players to stereo receivers. RCA audio cables come in pairs with two connectors on each end, a red one for right stereo and a white (or black) connector for left stereo. They are often bundled with video cables. Experts recommend gold-plated RCA connectors for extra protection against corrosion, especially if you live in a humid environment [source: Graves].

The other most common type of audio cable is speaker wire. Speaker wire runs from a stereo receiver to all speakers except the subwoofer (that requires a coaxial cable). Each speaker needs its own dedicated wire. Speakers not only receive audio signals via speaker wire, but also power.

Speaker wire is made from 99 percent oxygen-free copper and usually comes “unshielded,” which means you can see the copper conductor. Speaker wire comes in different thicknesses or gauges rated from 12 to 18 (thickest to thinnest). As a general rule, the longer your speaker wire, the thicker the gauge you should use. For speaker wire lengths up to 20 feet (6.1 meters) long, 14-gauge is sufficient, but anything longer than 60 feet (18.3 meters) requires 12-gauge wire [source: ecoustics.com].

Speaker wire is fairly simple, so you can get away with buying inexpensive, bulk wire. And don’t let anyone tell you that all of the speaker wires in your system need to be the same length. That’s a myth [source: Cobalt Cable].

Most audio recordings are digital nowadays, and there are several newer cables that specialize in carrying high-bandwidth digital audio signals. Optical digital cable (also known as fiber-optic and Toslink) transmits audio signals as pulses of light and is impervious to interference [source: ecoustics.com]. Another digital audio cable is called digital coaxial. It looks the old coaxial cables that connect satellite dishes or cable TV signals to televisions, except this is specially designed to carry digital audio. You’ll find optical and digital coaxial jacks on newer DVD players, CD players and stereo receivers.

The last type of audio-only cable is called analog multi-channel cable. This cable is designed for use with special players such as DVD-audio that play discs recorded at high sample rates for the maximum sound quality. Analog multi-channel cable consists of six to eight bundled RCA connectors, each responsible for a different audio channel on the back of a stereo receiver.

Video Cables

The most common type of video cable is called composite video. A composite video cable consists of one yellow RCA connector that’s usually bundled with red and white RCA analog audio cables. It’s called composite video because all of the video information — color, brightness and sync — is composited, or squeezed, onto one cable [source: Miller]. Composite video cables were designed for older TVs and have a maximum resolution of 330 lines. They’re fine for watching VHS tapes on the old TV in the basement, but if you have a newer television, or an HDTV, composite video cables simply won’t cut it.

S-video cables are a step up from composite video with a maximum resolution of 400 lines. You will recognize an S-video cable by its circular, nine-pin connector. S-video separates color information from picture information, resulting in a crisper image. Although S-video jacks are found on a lot of TVs, DVD players and home theater receivers, the cable’s initial popularity was quickly eclipsed by component video.

Component video cables consist of three RCA connectors colored red, green and blue. With component video, not only is color separated from picture, but the color portion is split into two separate signals [source: Miller]. The result is a super-sharp image with deep color saturation. Component video cables are ideal for connecting high-definition video components like Blu-ray players and HDTVs. Most home theater receivers come with several sets of component video jacks.

DVI (digital video interface) cables were designed specifically for use with HDTVs and other high-definition video components. They have large, 18-pin connectors that look like computer cables. DVI cables offer the exact same image quality as component video cables, except that DVI comes with a built-in copy protection protocol called HDCP (High-bandwidth Digital Content Protection). Critics of DVI claim the built-in copy protection mechanism causes compatibility problems with certain devices.

Audio/Video Cables

There are a handful of cables that transmit both audio and video signals. For years, coaxial video cables were one of the only choices for connecting video components. Coaxial video cables have that famous one-pin connector, sometimes called a stinger, that can either be pushed or screwed into place. Coaxial video cables are now mostly confined to outside connections, such as satellite TV or cable TV lines that come through the wall. A single coaxial cable carries both video and audio signals.

HDMI cables are an updated version of DVI. HDMI cables were also designed for use with HD components, but their connector is much slimmer, like a large USB cable. HDMI also includes HDCP copy protection. Manufacturers of HDMI cables tend to advertise their product as the only choice for connecting HD video components, but that’s not true. DVI cables work equally well. However, if you’re using an analog TV, all three work equally well [source: Cobalt Cable].

In Europe and the UK, the most popular dual-purpose cable is called SCART (Syndicat des Constructeurs d’Appareils Radiorécepteurs et Téléviseurs). SCART cables have fat, 21-pin connectors. In Europe, SCART cables do the work of RCA analog audio cables as well as composite, s-video and component video cables, but they can’t carry high-bandwidth digital video or audio signals, such as those necessary for high-definition TVs. HDMI is the preferred cable in Europe for HD components.

FireWire, or IEEE 1394, cables are mostly associated with connecting devices to computers, but a few high-end home theater receivers and HDTVs now come with FireWire ports. FireWire is capable of carrying compressed MPEG-2 video and digital audio. You might use a FireWire cable to connect a digital video camera directly to your home theater system to show off some unedited footage.

To sum up, here are the cables that you would use for some common home entertainment systems.

Home stereo system (CD changer, stereo receiver, speakers):

* Lower-end: If you’re playing regular CDs or MP3s, you’ll only need RCA analog audio cables and speaker wire.
* Higher-end: If you want crisper digital audio, go for optical or digital coaxial cables and thicker speaker wire.
* Highest-end: If you want the unparalleled sound of DVD-audio in full surround sound, you’ll need special DVD-audio cables and 12-gauge speaker wire.

Home theater system (Blu-ray player, DVD player or VCR, video game console, home theater receiver, TV, speakers):

* Lower-end: If you have an older standard-definition TV and mostly use your system to watch regular DVDs or VHS tapes, then you’ll do fine with a composite video cable bundled with RCA analog audio cables.
* Higher-end: For a newer standard-definition TV, you should really upgrade to component video cables. RCA cables will still do fine for audio.
* Highest-end: Once you enter the world of high definition, you’ll need to use either component video cables or one of the two copy-protected options: DVI or HDMI. You’ll also want to invest in thick-gauge speaker cable to make the most of your surround-sound system.

source:
http://electronics.howstuffworks.com/how-to-tech/cables-to-use.htm

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According to a recent poll, over 1/3 of you have your HDTV cords hidden behind a wall.

This may be a big violation of the National Electric Code that could void your insurance coverage.

    The National Electric Code (NEC) states:

    NEC ARTICLE 400 Flexible Cords and Cables General 400.1 Scope.
    This article covers general requirements, applications, and construction specifications for flexible cords and flexible cables.
    400.8 Uses Not Permitted.
    Flexible cords and cables shall not be used for the following:
    (1) As a substitute for the fixed wiring of a structure
    (2) Where run through holes in walls, structural ceilings, suspended ceilings, dropped ceilings, or floors
    (3) Where run through doorways, windows, or similar openings
    (4) Where attached to building surfaces
    Exception: Flexible cord and cable shall be permitted to be attached to building surfaces in accordance with the provisions of 368.8.
    (5) Where concealed by walls, floors, or ceilings or located above suspended or dropped ceilings

In other words, running power cords through the walls is not a substitute for permanent wiring. You’re supposed to have a new electric socket installed directly behind the TV, where you can plug in the power cord and coil up the slack to tuck underneath. If you drilled some holes and ran cable yourself all willy nilly, in and back out to a power socket, chances are you are in violation of these codes. Should a fire result, your insurance may find reason to get out of covering your losses. Naturally, it is in your best interests to hire a professional to check out your setup and make sure everything is as it should be. That having been said, let’s clarify the original poll and focus on how many of you might be on the wrong side of the NEC.

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