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When a new technology comes to market, it is typically first found in the more expensive segments of a given product category. When GM™ introduced airbags in the mid-1970's, Cadillac was chosen to be the first car to provide this option, offering both driver and passenger airbags. Then the trickle down process begins. As the new technology becomes proven and other market factors take hold such as swelling market demand and economies of scale, it begins to trickle down into mainstream products. Today even the least expensive cars offer dual airbags as standard equipment. The same phenomenon is taking place with the High-Definition Multimedia Interface (HDMI) connectivity standard. Previously found only in high-end audio/video devices, HDMI technology is finding its way into mainstream consumer audio/video products. As HDMI takes hold, more and more products are surfacing in support of HDMI and the needs of the surging residential and commercial audio/video market.

The HDMI connectivity standard combines both uncompressed digital audio and video into a single compact interface and supports bandwidth speeds of up to 4.95-Gbps. Instead of using separate and often bulky cables for analog audio and video transmission, with HDMI only a single cable is needed for a high-resolution, all digital signal transmission. HDMI is an outstanding connectivity solution and it's no wonder its popularity is spreading; however HDMI technology isn't without its challenges. HDMI cables are known for having a length limitation of about 5 meters. Copper cables longer than 5 meters in length often just don't work. The cable's impedance (resistance to sending the signal) increases as the cable length increases. At about 5 meters, the resistance is too high to pass the signal. Unlike analog video transmission that can display varying degrees of picture quality, HDMI digital video transmission either works or it doesn't, it will display a picture or it won't. This HDMI signal loss phenomenon can be described as "falling off a cliff" meaning there is no middle ground. This isn't completely true, since an inferior HDMI cable can introduce some digital artifacts into the picture, but as a general rule this is a good description of HDMI signal loss.

A 5-meter HDMI cable limitation is a serious problem since many audio/video applications require its cabling to reach beyond 5 meters. Some products have come to market, such as fiber optic cables, allowing for long HDMI cable runs beyond 5 meters. Traditional HDMI cables transmit a digital signal over copper conductors were fiber optic cables use light pulses to send the audio/video signal over clear plastic or glass fiber conductors. Since it has little or no impedance, fiber optic technology allows for a very long cable runs. The biggest barrier to fiber optic cabling is its price. Often running into the four-figure price range, this solution isn't economically viable for many audio/video applications. Another option is to use an HDMI extender, also known as a booster box, to achieve a long cable run. An HDMI cable runs from the video source (i.e. DVD player) to the extender. A second HDMI cable of similar length is plugged into the extender and then is connected to the display. The HDMI extender amplifies the incoming signal before resending it over the second length of HDMI cable effectively doubling the length of the cable run. This is a good solution if the cable is not going to be run in-wall. A survey of HDMI amplifiers was unable to identify any that are Underwriters Laboratories (UL) listed for in-wall installation. Fire safety is an important consideration when running cables in-wall. Since long run HDMI cables are typically installed in-wall, an HDMI extender may not be the best solution for certain long run applications.

Some HDMI cable manufactures have increased the thickness (gauge) of the copper conductors within the HDMI cable to lower the cables impedance (resistance) to passing the signal and in effect allowing for a longer cable run. A typical HDMI cable is constructed using 28AWG copper conductors. These larger, heavy gauge cables use thick 24AWG copper conductors. This construction allows for a cable length of up to 15 meters. Certain brands of heavy gauge HDMI cables may not be constructed to support 1080p resolution. Supporting 1080p resolution may not be important today since many HDMI devices have a maximum resolution of 720p or 1080i. With more 1080p products coming to market, scalability is an important consideration, and installing a long run cable that may need to be replaced in the foreseeable future is likely not a good investment. A new product to consider for long run applications is an HDMI cable with a built-in signal amplifier made by Accell. These UltraRun™ brand cables are engineered using a miniature signal equalizer and amplifier integrated into the connector end of the cable. By connecting the amplified end of the cable to the display, the cable boosts the signal, providing runs in length of up to 45 meters. The UltraRun cable supports resolutions up to 1080p and are UL Listed and CL3 rated for in-wall installation.

If you're looking to setup an audio/video system in a home or business, HDMI connectivity is certainly worth considering. For long run applications, there are many options available to ensure a successful, trouble-free installation.

Michael Weizer is Director of Marketing for Accell Corporation. Accell, a wholly owned subsidiary of BizLink Technology, is a member of the HDMI trade organization. Accell is focused on the design, manufacture and delivery of affordable, high quality audio/video cables and interconnects. For more information, please visit our Web site at www.accellcables.com.