Equipment & Technical Issues

Single-channel video, by definition, involves one information source, such as a DVD, one playback device, for example a DVD player, and one display mode, such as a monitor or projector. This set-up is familiar to anyone who owns a TV set and DVD player. However, although the basic principles for exhibiting single-channel video might appear straightforward, there are important technical standards for professional media art exhibition. Proper selection, installation and maintenance of video and audio equipment are critical, and exhibitors should consult qualified technicians where possible. These choices have an impact beyond the purely technical. For example, the decision to project a work in a theatrical setting or to show it looped on a flat-screen monitor in a gallery will be tied to a range of variables, including the exhibition space and design, media formats, playback equipment and display devices, and budget. Perhaps most significantly, these equipment and technical decisions should also speak to the artists' intentions, as they will impact the meaning and perception of the work.

This section provides recommendations and outlines of standard media exhibition formats, playback equipment and display devices for both video and audio. The section also includes a projector installation guide and general technical and equipment troubleshooting tips.


Media Exhibition Formats & Playback Equipment

Display Devices

Video Cables

Audio Components

Projection Installation Checklist & Guidelines

Common Questions & Other Considerations



Media Exhibition Formats & Playback Equipment
Preferred media formats and playback equipment for exhibiting single-channel video works are specific to the presentation environment and the artist's work. For example, VHS is only acceptable for classroom or reference viewing, a well-authored DVD is suitable for looped exhibition in a gallery space, and DVCAM is an excellent format for cinematic presentation. Hard drive playback is also a viable option for the presentation of single-channel video if rights are cleared for compression/digitization, and if the exhibition institution has the technical and financial resources to accommodate this exhibition mode. (For a more detailed discussion of hard drive playback, visit Computer-based Arts Equipment & Technical Issues.) Explanations and recommendations regarding exhibition formats and playback equipment are given below. For a more comprehensive discussion of media formats please visit the Formats section of the Resource Guide.

DVD		 DVD (Digital Video Disc) is among the preferred formats for exhibiting single-channel works in a gallery or museum environment. DVD, introduced in 1995, is an optical disc storage technology that shares the same overall dimensions of a CD but has a much greater storage capacity. It uses MPEG2 compression to encode 720:480p resolution and full-motion video, and Dolby Digital to encode 5.1 channels of discrete audio. This also makes DVD an option for the exhibition of works with up to 5.1 channels of surround-sound. DVD is not a failsafe medium; there are a number of important considerations to keep in mind.

There is an enormous quality spectrum when it comes to DVD authoring. A poorly encoded DVD will result in image and sound fraught with digital artifacts, unwanted pauses, unpredictable interruptions, and distortions. It is critical to allow for ample time to test, and potentially replace, your exhibition copy prior to installation. Another important part of DVD authoring is the loop function. If the work is to be looped (repeated continuously throughout exhibition hours), the DVD should be programmed to accommodate this during authoring.

There are many different manufacturers and types of DVD-R (recordable DVD) stock. The manufacturer and quality of your media stock will impact its compatibility with playback equipment and its overall reliability. Professional DVD players are designed to run continuously without failure. Most professional models have serial ports (RS-232) allowing computer control and synchronization of multiple DVD players and are also multi-standard, playing back both NTSC and PAL DVDs. DVD media is rapidly evolving. DVD-R Gold is a relatively new format which claims an archival life. These discs are considerably more expensive. In the near future HD-DVD and Blu-ray Disc will be available; these discs will have much greater storage capacity, and thus will accommodate video encoded at higher rates.


DVCAM		 DVCAM (not to be confused with MiniDV, which most consumer camcorders use) is the preferred format for a cinematic or theatrical screening. Although it is of superior technical quality to DVD, DVCAM cannot be shown as an endless loop, and is thus less desirable for unattended gallery and museum exhibitions. Developed by Sony as part of the DV format and introduced in 1996, DVCAM transports tape 50 percent faster than DV (digital video) and MiniDV, resulting in a higher track width, which can store more information and result in a higher quality image. The codec used is the same as DV, but because of the greater track width available, the data is much more robust, resulting in 50% less dropout. DVCAM is a professional/industry-level product, and playback decks are designed for high quality playback, with many output options accommodating numerous cable configurations.

Betacam SP		 Betacam SP (commonly called Beta SP) was introduced by Sony in 1986, and remains an excellent format for cinematic screenings or theatrical environments. Betacam SP (for "Superior Performance") increased horizontal resolution to 340 lines over the early Betacam’s 300 lines. Beta SP was the industry standard for most TV stations and high-end production houses until the late 1990s. Typically only larger institutions can accommodate presentations on Beta SP due to the relatively high cost of the playback equipment. Betacam SP is also a professional/industry level product.

VHS 		VHS (Video Home System), which was introduced by JVC in 1976, is recommended as a reference or classroom viewing format and is not acceptable for public exhibition. A VHS cassette contains a 1/2-inch-wide magnetic tape wound between two spools, allowing it to be slowly passed over the various playback and recording heads of the video cassette recorder. The quality of a VHS tape degrades significantly after repeated playing, and when projected results in a substantially compromised image. As VHS was the consumer standard during the 1980s and 90s, a wide range of decks are still in circulation. Only professional models should be considered for playback; lesser decks are much more prone to “eating” tapes.


Display Devices
Display options for single-channel video works range from free-standing video monitors and wall-mounted plasma screens to small projections on a gallery wall or large-scale projection on a screen in a theater. The choice of display device depends on a range of variables, including the presentation environment and the artist's work. Early single-channel video works, such as Joan Jonas's Vertical Roll (1972), may be best suited for exhibition on a monitor, while a new, digitally-produced work, such as Pierre Huyghe's A Journey That Wasn’t (2006), may be better served by a plasma screen or a projection. The following is an outline of common display equipment for single-channel video or media works.


Video Monitors

Video monitors have until quite recently been the most commonly used display devices for the exhibition of video and media art works. Monitors, including presentation monitors and flat screens such as plasma and LCD, can supply a bright, focused image under various lighting conditions, although ambient and direct light will still affect the displayed image and the optimum viewing angle. The video monitor has an important history in relation to early single-channel video works. Works that make a specific technological or conceptual reference to the video monitor or "box" should be shown as such. The artist's intention and the content of the work are vital factors in determining the appropriate display equipment.

Note: CRT (Cathode Ray Tube) technology was first implemented by German physicist Karl Ferdinand Braun in his 1897 oscilloscope. CRT is a specialized vacuum tube in which images are produced when a moving electron beam strikes a phosphorescent surface. Until recently CRT technology was traditionally used in oscilloscopes, televisions, video monitors, and computer displays. This three-gun technology, red - green - blue, will soon be completely replaced by flat screens (LCD and plasma). In 2005 Sony announced that it would stop the production of CRTs. Numerous early video works were made with CRT technologies as a direct or conceptual reference. As CRT technology becomes obsolete, careful consideration must be given to the presentation of these works. Visit the Preservation discussion of this issue.


Presentation monitor		   Presentation Monitor. A presentation monitor is designed with resolution, quality, and durability in mind. Used in industrial, corporate and exhibition contexts, these monitors have a substantial shelf life, can sustain constant playing, and come with professional video inputs that can accommodate high-quality data transfer. Recent models also include a "wide screen" display feature that can play both 4:3 and 16:9 aspect ratio footage without distortion. Presentation monitors do not typically include built-in speakers, and must be paired with either self-powered or amplified speakers for exhibition of works with sound.

Consumer television		   Television. Consumer-grade televisions are not designed with the wear and tear of exhibition in mind and cannot compete with the general durability and lifespan of a presentation monitor. An exhibitor acquiring equipment for the long term should invest in a monitor rather than a television. Avoid units that have built-in DVD or VHS playback systems, as one element will inevitably break before the other, debilitating the equipment in an exhibition environment.


Flat Screens

Flat screens are increasingly common in single-channel exhibition – providing a potentially elegant and aesthetic alternative to projector installations while using a minimum of space. More often than not, flat screens do not come with internal speakers for audio playback. It is important to make sure that the screen can accept input from the playback device you are using. There are two distinct types of flat screens: plasma and LCD. These technologies use fixed-pixel arrays, which means they have rows and columns of individual picture elements that turn on and off to produce the necessary patterns of light.

With flat screens, one must consider aspect ratio, which refers to the relationship or ratio between the width of the image and the height of the image. There are two standard aspect ratios: 4:3 and 16:9. A standard TV has an aspect ratio of 4:3, which means that the picture is four units wide for every three units of height. HDTV standard is 16:9, which is 16 units of width for every 9 units of height. These ratios are also expressed as 1.33:1 and 1.78:1. 16:9 better accommodates wide-screen formats, common in commercial film since the 1950s. Most commercial films produced in the last 50 years have ratios of either 1.85:1 or 2.35:1.

Plasma		   Plasma display devices have higher resolution than most conventional TV sets, and are capable of displaying full HDTV and DTV signals as well as XGA, SVGA, and VGA signals from a computer. Most plasma monitors can accept any video format. There are two types of plasma screen: EDTV (for “enhanced definition television”) and HD. HD-compatible screens are capable of displaying full-resolution HD-standard video, most often from commercial DVD or television broadcast, and are compatible with less robust formats. Plasma screens have no scan lines because each and every pixel cell has its own transistor electrode. This creates a smooth, evenly lit image across the entire surface of the display. Most current displays also include built-in line doubling to improve image quality from low-resolution video signals. Plasma screens also provide uniform brightness, illuminating all pixels evenly across the screen, and offer a viewing angle of 160 degrees (top to bottom and left to right) - much better than rear-projection TVs and LCD displays. This allows a larger number of viewers to enjoy proper image reproduction from a wider variety of locations throughout the exhibition space. One drawback: Because plasma screens use phosphors to generate light, they can be subject to "burn-in" - that is, when a static image is left on the screen for a long time, it may not completely disappear when the image changes.

LCD		   LCD screens typically range from 15-inch models designed primarily as computer monitors up to 37-inch wide-screen designs complete with speakers and TV tuners. LCDs have lower contrast ratios than plasma screens, primarily because they have a harder time reproducing deep black and dark grays. They also tend to be one to several inches thicker than plasma screens and have a narrower effective viewing angle. Among their advantages, LCDs are completely immune to burn-in, and they more often include all the standard features of a conventional TV. LCDs also run cooler than plasmas, minimizing the need for potentially noisy fan cooling.

Video Projectors

Projection has become an increasingly common mode of display for video artworks, both in darkened galleries and in cinematic or theatrical settings. Video projectors have advanced dramatically over the past 10 years. Today, important specifications to keep in mind when acquiring or renting a projector include resolution, throw distance, and video/audio inputs. Projector brightness is measured in ANSI lumens. A minimum of 1200 lumens is recommended for projections that will compete with ambient light. The more ambient light in your exhibition space, the higher a lumen count will be necessary to project a strong image. Click here for a useful lumen guide. Brightness uniformity is the percentage of brightness present from corner to corner and edge to edge of the projected image. A uniformity rating of 85 percent or better will yield a consistent image. Projector bulbs have an expected operating time, called lamp life, which is measured in hours. Newer models claim 4,000 hours of lamp life. It is recommended to keep a record of how much use your bulb has endured in order to avoid a bulb burning out in the middle of an exhibition or screening. There are two major types of projectors: liquid crystal display (LCD) and digital light processing (DLP).


LCD
  LCD (liquid crystal display) projectors are thought to offer better color accuracy and exhibit superior light efficiency over DLP.

DLP

  DLP (digital light processing) projectors have higher contrast ratios, resulting in deeper blacks and richer colors than LCD. A DLP image is typically smoother and can better disguise pixelization or an effect that results in a "screen door" like image.

Projection Screens

Well-designed projection screens will reflect more light than a matte-white wall; some screens are also designed to alleviate ambient light problems. The term “gain” is used to describe the amount of light reflected by the screen, using a matte-white wall as a reference. Use of a screen or projection paint increases an image’s brightness and contrast by efficiently directing the projected light at the viewer.

Video Cables
When choosing the type of cable used to connect the playback deck to the display device, be aware of the substantial spectrum of quality in the cable manufactured today. Cables should come from a reputable manufacturer and be composed of professional-grade parts. Video cable choices include digital (HDMI, etc.), component, S-Video, and composite. Both digital coaxial and fiber optic cables can carry multi-channel surround sound audio on a single cable.

HDMI cable

   HDMI (High-Definition Multi-media Interface) is an industry-supported, uncompressed, all-digital audio/video interface. HDMI is a descendant of DVI (Digital Visual Interface).

Component cable

   Component cables transmit analog video information as two or more separate signals. In the adjacent illustration three RCA com cables form the component video with combinations of the red, green, and blue signals that make up a television image.


S-Video cable

   S-Video is also considered a component signal because the luminance (black and white) and chrominance (color) signals are transmitted on separate wires. S-Video is a single cable that does not include audio.


Composite cable
   Composite, the oldest of video signals and still prevalent, combines both color (chrominance) and black and white (luminance) in one signal. This feature originally allowed for backwards compatibility with black-and-white televisions receiving off-air broadcasts, but created image problems not found in later S-Video or component signals. Today, a typical composite video signal uses a single coaxial wire, a yellow RCA connector for video, and a white and red RCA connector for stereo audio. A BNC connector is frequently found in professional applications.
Audio Components
Sound is a critical component of most moving image media art, and yet it is the technical element most often overlooked when installing and presenting single-channel works. If you plan to amplify sound, rather than provide viewers with headphones, it is important to consider how sound will be contained and focused if multiple works will be shown in the same space. The following is a guide to common audio components, including speakers, amplifiers, mixers and cables.


Amplified Speakers

Speakers come in a wide range of models; the best speakers for delivering audio in a large exhibition space are PA (public address) models, designed for projecting audio at high fidelity across all frequencies. Studio monitors, designed for high quality projection in small, quiet spaces, are acceptable for certain spaces or types of exhibition. Both come in active and passive models (defined below). There are other, more specialized options for projecting audio in a single-channel format. Parabolic speakers, often used as a solution for competing sound elements in a single exhibition space, can help focus sound amplification to a specific viewing/listening area. Focused sound projection is further developed in a relatively new technology called "Audio Spotlight," where sound is audible only when one stands within a specified path. Finally, headphones isolate audio on a single viewer; a headphone mixer can accommodate multiple viewers/listeners.


Self-powered Speakers
   Self-powered speakers are best exemplified by the stereo speakers that accompany your desktop computer. They require no external amplifier, as the amplifier is built into the speaker cabinet. Consumer grade self-powered speakers can sometimes be sufficient for an extremely intimate exhibition space, but for most exhibition environments they do not provide an adequate spectrum of sound nor sufficient volume. Professional quality self-powered speakers exist, but in certain circumstances, use of self-powered speakers in installation environments leads to “ground hum” - an audible 60 hertz hum or visible light rolling bars in the video image. This can occur when speakers are plugged into a different AC circuit than the video equipment, as is sometimes required in large presentation spaces. Also, the cables connecting the playback device to the self-powered speakers are prone to noise and interference when run over long distances.


Passive Speakers


   Passive speakers are used in conjunction with an audio amplifier. The amplifier’s wattage should be compatible with the watt capacity of the speakers. For example, a 200-watt amplifier should be used with two 100-watt speakers. For most exhibition spaces, 100 watts per channel (or number of speakers) will be more than sufficient.



Surround Sound		   Surround sound is required by some single-channel video works. It is important to correctly identify how many channels are needed. The most common surround sound ratio is 5:1 or 5 speakers:1 sub-woofer. This system has become popular with home theater enthusiasts in recent years. Note that one can easily find inexpensive 5:1 surround sound packages in the consumer market, but one gets what one pays for. There is no need for a pre-packaged system as long as you have the correct number of speakers, and your amplifier and audio playback equipment can accommodate surround sound. Choosing speakers with high, mid, and low range frequencies will yield the best results.



Audio Amplifiers & Mixers

Audio Amplifier
   An audio amplifier is required if your speakers are not self-powered. Using an amplifier with quality passive speakers will allow for greater volume than self-powered speakers. It is important to make sure that the wattage capacity of your amplifier is compatible with your speakers. For example, if your amplifier can support 100 watts on each channel, use 100-watt speakers. Many amplifiers also include limiters, low frequency filters, and overload protection, though additional equipment can yield greater control. There are many distinctions between consumer (“home stereo”) and professional amplifiers. Professional equipment is designed for maximum sound fidelity at any volume, and is built to sustain longer hours of use.

Mixer
   Mixers are used to adjust audio signal and send it from different playback (or live) sources to amplifiers and speakers, or to send signal from a device with RCA outputs to an amplifier that only accepts XLR (defined below). Depending on the technical requirements of an exhibition, a mixer may or may not be necessary. Professional mixers come in many sizes, with different functions depending on size.


Headphones

Headphones are a pair of transducers that receive a signal from a playback device and amplify that signal with speakers placed close to a listener's ears. When using headphones in an exhibition environment, earbuds, like those commonly used with iPods, should be avoided for reasons of sanitation and comfort. Although headphones can technically accommodate stereo (left and right) audio signals, the spatial qualities of a composition, present when amplified with speakers, can be lost. While headphones are an excellent solution for isolating sound in a space with multiple works, it is important to consider what elements—aural, visual, and environmental—may be compromised as a result.


Audio Cables

Like video, audio cable choices include digital (HDMI, etc.), RCA, XLR, 1/4"/TRS, and Speakon.


HDMI cable

   HDMI (High-Definition Multi-media Interface) is an industry-supported, uncompressed, all-digital audio/video interface. HDMI is a descendant of DVI (digital visual interface.)

RCA
   RCA, also called phono plug, was introduced in the 1940s to connect phonograph players to radios. Stereo RCA cables are usually color coded red and white, left and right. Anyone with a television and VHS or DVD player at home will likely be familiar with these cables which are commonly used with consumer electronics.

XLR
   XLR plugs and sockets are used mostly in professional applications. The most common is the 3-pin XLR3, used almost universally as a balanced audio connector for high quality microphones and connections between equipment. It does not appear on consumer playback devices.

1/4"/TRS
   1/4”/TRS (tip/ring/sleeve) jacks and plugs are an extremely common audio connector, especially for the original 1/4" size, but are also available in 1/8” size or mini. This is in contrast to the terms phono plug and phono jack, which refer to RCA connectors. This type of audio cable comes in two-conductor (mono) and three-conductor (stereo or tip/ring/sleeve) versions.

Speakon
   Speakon is a type of cable connector commonly used in pro audio systems for connecting loudspeakers to amplifiers. It features a quick-locking system with options for soldered or screw-type solderless connector for easy repair in the field. Additionally, it provides a fully insulated connection to equipment, eliminating electrical shock risks associated with high power audio amplifiers. The speakon connector is an alternative to 1/4", two-pole twist lock, and XLR connectors for loudspeakers.

Projection Installation Checklist & Guidelines
The proper installation of a video projection system is critical to professionally and accurately displaying an artist's work. The following is a checklist and set of guidelines for proper projection installation.




Ceiling mounted projector
for both front and rear
projection.


Top view


Tabletop or plinth mounted projector for both front and rear screen projection.

  Ceiling Mount Checklist.
  • Verify the desired image size and the projector throw distance (the distance between projector and screen).
  • Verify that the projector can achieve the image size within the given throw distance. Consult the manual.
  • Identify any potential obstructions that will affect projector mounting, such as ceiling HVAC vents or lighting systems. Identify any obstructions to the projected beam, such as hanging light fixtures, structural beams, etc.
  • Before mounting the projector, ensure that the mounting surface does not vibrate. Vibration is typically caused by heating/cooling ducts that can subtly shake ceilings in certain situations.
  • Ensure that heated air from ducts is not blowing on projector.
  • Check that the source of power for the projector is not controlled by a light switch, as is an outlet intended for a reading lamp. Improperly switching the power off can damage projector bulbs. Projectors have internal fans that cool the bulb and components. In most cases, the larger the projector, the louder the fan. If the installation has subtle audio or is silent, the fan noise will be more audible. In addition, a small amount of light is generally emitted from the fan vent. As a solution for both problems, the projector can be placed in a separate room with a glass projection window, similar to the projection booths used in movie theaters. As always, adequate ventilation must be ensured for the proper functioning of video projectors and DVD players.

    Proper installation will eliminate image distortion. Avoid keystone correction as this process may produce visible artifacts, generally most noticeable at the edges of the frame.

    When ceiling mounting a projector, remember that not all projector lenses are center-mounted. If the lens is offset, this must be compensated for when installing the mount. Otherwise the image will be slightly keystoned.

    When providing viewer seating, be sure that there is a comfortable distance between the seating and the screen. The distance from the viewer to the screen can be calculated as 1.5 - 2 times the width of the image. For example: a 10-foot-wide screen dictates a viewing distance of 15-20 feet.

    Professional projector mounts are highly recommended when hanging ceiling mounted projectors. Aside from the serious issue of safety, it is simply not cost effective to make your own projector mount. Commercially available mounts provide the necessary control and rigidity lacking in even the best “home-made” mounts. Furthermore, great amounts of time are saved during installation and maintenance when using off-the-shelf mounting solutions.


    • Common Questions & Other Considerations

    Analog and Digital Media
    "Analog" refers to a system of recording video images that employs continuously varying waveforms to encode brightness, color and the timing information necessary to reproduce a moving image. Examples of analog video formats are VHS, Betacam SP, and 1/2" reel-to-reel tape (obsolete). Digital media formats include DVD, Digital Beta, DVCAM, and MiniDV. With the exception of DVD, these formats are similar to analog video in that they consist of physical magnetic tape reels stored inside protective cassettes. The critical distinction is the way in which the information is stored. (Digital data is stored as a series of 1's and 0's, while analog data uses a range of numbers such as 0 to 10,000.) When examined closely, analog video appears as a series of lines, while digital video is comprised of pixels, or tiny boxes of color. The difference between analog and digital formats, though subtle, is perceptible.

    International Standards: NTSC and PAL
    NTSC and PAL are the two main video broadcast standards or systems; they are incompatible with one another. Developed in 1953 in the U.S., NTSC (the acronym for National Television System Committee) is the video standard used in North America and Japan. NTSC videocassettes and DVDs are only playable on equipment that supports this standard. NTSC displays 525 lines of information at 60 half-frames (interlaced) per second. PAL stands for Phase Alternating Line and is the dominant television standard in most of the world, including Europe. PAL delivers 625 lines of information at 50 half-frames per second, which typically results in a higher-quality image. PAL videocassettes and DVDs are playable only on PAL equipment. (A third, much less common format is SECAM [Sˇquentiel Couleur Avec Mˇmoire], which was engineered in France.) Multi-standard playback devices can read all international formats.

    Standard Definition and High Definition
    Standard-definition television or SDTV refers to television systems that have a resolution that meets standards but not considered high definition. VHS tapes, DVDs, BetaCam SP, DigiBeta, and DVCAM, are all standard definition formats. High-Definition television (HDTV) refers to the broadcasting of television signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. HDTV is broadcast digitally, and therefore its introduction sometimes coincides with the introduction of digital television (DTV): this technology was first introduced in the USA during the 1990s, by the Digital HDTV Grand Alliance. HDTV is defined as 1080 active interlaced lines, or 720 progressive lines. 16:9 aspect ratio in ITU-R BT.709. The term "high-definition" can refer to the resolution specifications themselves, or to media capable of similar sharpness such as motion picture film.

    Addressing the Ambient Environment
    The environment will significantly impact the exhibition of single-channel video. Unless properly planned for, ambient light and sound can dramatically impair the presentation of these works. Please visit the Planning Process and Best Practices sections of the Resource Guide for detailed recommendations.

    Inadequate Ventilation of Projectors and DVD Players
     Projectors and amplifiers that overheat will shut themselves off. Improperly ventilated DVD players will cause the DVDs to warp as they heat up, which can cause skipping and other malfunctions. Commonly an overheated DVD will exhibit problems as the day progresses and the DVD player heats up. If skipping is caused by heat buildup, cleaning the disc will not help and in fact may damage the DVD. Only ventilating the DVD player will prevent such difficulties.

    Ground Hum
    Ground hum is an audible hum or light rolling bars in the video image. When possible make sure all equipment is plugged into the same electrical circuit, or at least the same electrical “leg.”

    Leaving Projectors on Continuously
    Leaving a projector on continuously can significantly reduce the projector bulb's rated lifetime.

    Color Bars
    Color Bars are inserted at the beginning of a video program to allow for the proper tuning of a television’s or projector’s brightness, contrast, and color settings.

    Test Tones
    Test Tones are usually included with color bars and consist of a simple tone for testing speaker response and adjusting audio levels. A complete set of test tones (ranging from 20Hz to 20kHz, the average limits of human hearing) can be used for more specialized testing and tweaking of an audio system.

    Other Electrical Considerations
    Electrical considerations for exhibitions concern the placement of playback devices, amplification, speakers, and power and A/V cables. Power outlets should be checked to verify they can handle the needed output (when using projectors, amplifiers, etc. it is easy to blow fuses) and to ensure that the power output is clean and consistent. It is best to keep all power and A/V cables away from visitor traffic, but if cable must be run through exhibition space, the entire length must be carefully taped (use duct tape) to prevent accidents.