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Information Services-

Audio Visual Technology

REQUIREMENT FOR DESIGN, SPECIFICATION, AND

INSTALLATION

Last updated

By Carolyn Wood

On June 2014

This document and other Information Services documents are

held online on our website: https://staff.brighton.ac.uk/is

University of Brighton Information Services

Page | 2 Last Updated 17th July 2015

Contents

Introduction ...................................................................................................... 3

Common Design Principles .............................................................................. 3

Screen Sizing and Lines of Sight .............................................................. 3

Furthest Viewer ......................................................................................... 3

Closest Viewer .......................................................................................... 4

Horizontal Viewing Angle .......................................................................... 4

Screen Position ......................................................................................... 4

Vertical Viewing Angle .............................................................................. 4

Applicable Standard and Regulations .............................................................. 5

Project Management Process .......................................................................... 5

AV Wiring and Cabling Requirements .............................................................. 6

Connection Plate Requirements ....................................................................... 7

Containment .................................................................................................... 7

Power and Data Services ................................................................................. 8

Drawings .......................................................................................................... 8

Rack Building ............................................................................................... 9

Assistive Hearing Systems ........................................................................... 9

Fixtures and Fittings ..................................................................................... 9

Commissioning and Handover .....................................................................10

Network Configuration .................................................................................10

Software Configurations ..............................................................................10

Security .......................................................................................................11

Accessories .................................................................................................11

Display Systems ..........................................................................................11

Audio Systems ............................................................................................14

Computer ....................................................................................................15

Multimedia Playback....................................................................................15

Visualizer (Document Camera) ....................................................................15

Auxiliary Inputs ............................................................................................15

Signal Processing ........................................................................................16

Control System ............................................................................................16

System Furniture .........................................................................................16

Acoustic and Lighting ..................................................................................16

References ..................................................................................................17

Information Services- Audio Visual Technology

Printed Wednesday, 29 July 2015 Page | 3

Introduction

The University operates around 160 centrally bookable teaching rooms and possibly an equivalent number in departmental teaching spaces. Almost all of these rooms utilise audio visual (AV) technology as an aid to teaching delivery. Timetabling in to these centrally bookable rooms is done by Estates and Facilities Management (E&FM) on the basis that all rooms are available to any school and can be used by all departments. Support for the AV systems within these areas comes under the remit of Information Services (IS). This requires both E&FM and IS to ensure that centrally booked rooms are designed and equipped to support the broadest range of general teaching activity. The technology deployed in departmental rooms, while focused on the more specialist needs of particular subject areas should still offer a user experience that is consistent with that offered in the central rooms. This will become increasingly important as the University adopts new technologies and functionality, for example lecture capture. The exact specifications of each AV system will consider a wide range of factors, some of which are explored in this document. Specifications are further complicated by the constant and rapid evolution of the technology, particularly as it moves from analogue to digital solutions and it is for this reason that specific brands and models are not mentioned in this document.

This document intends to provide an overview of the typical technology that would be used in teaching spaces and offer guidance on a number of pre-requisites as well as how that technology might be specified, installed and managed. Professional assistance should always be sought from IS when designing any AV system.

Common Design Principles

This section provides common elements required of the whole solution or each room, unless specifically mentioned elsewhere within the document.

Screen Sizing and Lines of Sight

Optical calculations will need to be performed for each space, to ensure that industry guidelines are applied. For each teaching space where this is not physically possible, the arrangement of that space shall be clearly identified and approved by Information Services before being implemented.

Furthest Viewer

No student will be positioned further from the screen than six screen heights.



Closest Viewer

No student will be positioned closer to the screen than two screen heights.

Horizontal Viewing Angle

To view the centre of the main screen, no student will be required to turn more than 45 degrees to left or right.

Screen Position

The base of the screen (excluding interactive boards) will be at least 1200mm above the floor at the front of the teaching space.

Vertical Viewing Angle To view the centre of the main screen, no student will be required to look more

than 15 degrees above horizontal.

Category Type

A Large Format Lecture Theatre typically with 2x HD projectors (dual screen),16:9 format, long throw projection lenses, fixed frame projection screens, Extron touch-screen control system, presentation matrix switcher, DVD player, Visualiser, radio microphones, audio mixer, audio amplifier, speakers, 2 -bay lectern, laptop input, dedicated PC input, induction hearing loop (single loop), with installation, programming & commissioning. . Capacity 100+

B Medium Format Seminar Room typically with 1x HD projector, 16:9 format, long throw lens, fixed frame projection screen, Extron touch- screen control system, DVD player, Visualiser, radio microphone, audio mixer & amplifier, 2 -bay lectern, laptop input, dedicated PC input, induction hearing loop with installation & commissioning. Capacity 30/35 -100

C Small Seminar/Committee Room typically with WXGA/HD projector 16:9 format, fixed frame projection screen, Extron button panel control system, DVD player, Visualiser, radio microphone, audio mixer & amplifier. (Alternative configuration - SMART interactive wall mounted projector , SMART Notebook software, laptop input, dedicated PC input, USB2.0, VGA and Audio input via the interactive projection screen.) Installation & commissioning is included. No induction loop. Capacity 30/35



D Group Study/Small Meeting Room typically with a 50"-60" wall mounted LCD monitor with laptop input, VGA,HDMI and Audio input directly to the wall mounted monitor. The speakers are integrated in to the monitor and inputs are wall mounted for laptops and audio. A smaller Extron button-control system is also supplied. Installation & commissioning is included. No microphones, no Visualiser, no DVD and no induction loop. Capacity up to 25-30

Applicable Standard and Regulations

PAS 122:2009 and the latest versions of all standards quoted within or their replacements.

The Control of Artificial Optical Radiation at Work Regulations 2010.

University Conditions of Use for Networks and Computers

University Health and Safety policy

University Financial Regulations. E&FM Electrical Contractor Use Policy IS Network/Data Contractor Use Policy

BS 7594:2011- Code of Practice for Audio Frequency

Project Management Process

Where AV is a component of a larger building project then the project would be managed by E&FM with IS managing the AV in conjunction with the Project Manager. IS will provide, in conjunction with the University’s preferred AV contractor, the AV technical specifications, schematic drawings and quotes.

It is expected that the successful construction contractor used by E&FM on projects will use the University’s preferred AV contractor under a sub-contractor arrangement.

Where a project consists entirely of AV work, the project would usually be managed by IS with related M&E works managed via E&FM.

For schools/departments wishing to run their own AV projects, IS can provide, in conjunction with the University’s preferred AV contractor, an AV project management service which would include design, specification, installation and commissioning. Procurement of the equipment will need to comply with University Financial Regulations and be in line with that used within central teaching rooms, with the order being placed from the schools/departments budget.



In all cases the AV contractor will nominate a named project manager who will be the main point of contact throughout the project. This person will not change during the contract, and will be available for the majority of the contract duration. This person will attend site regularly and will not normally be a member of the installation team. In addition the AV contractor can provide if required a project schedule in Gantt format as an Excel (.xlsx) or MS Project (.mpp) file, as well as circuit diagrams and method statements. Any variations or amendments to the AV design or specification will need approval by IS. If changes are detrimental to the agreed functionality of the system, the client/steering group will also be consulted and their approval obtained.

The AV contractor will complete all AV work to the standards specified in the project quote/tender, SLAs and approved amendments. IS will provide post construction commissioning and snagging of AV installations and produce a snag list for the AV contractor. On projects managed by E&FM, they will issue the snag lists via the Main Contractor and Project Manager. Final invoices for the AV contractors should not be paid until IS has signed off the installation work.

AV Wiring and Cabling Requirements

All wiring and cabling must conform to current Health and Safety legislation, be safe with no sharp edges and good cable management undertaken. Any installed cabling must be low smoke zero-halogen type. Any electrical wiring and cabling must be undertaken by an approved electrician and managed through E&FM. The AV contractor should undertake any electrical wiring. Any data/network cabling must be undertaken by approved contractors and managed through IS. Any switches or hubs used as part of the AV installation will need to be done with the approval of IS. Power, Data and AV Cables are to be routed separately within racks and segregated in cable management dado trunking.

All wiring must be new, cables and connectors are to be industry standard, of good quality and from a reputable manufacturer. Cable connectors and plugs must be fitted appropriately. For example, screw fixings must be suitably tight and BNC bayonets must be correctly crimped and booted. Cable hoods should be fitted, and strain reliefs clamped onto the outer sheath of the cable where appropriate. The use of adaptors must be agreed in advance.



Cable types used will be consistent throughout a project, be able to pass the correct bandwidth for the signal type must be of the correct length for the task (coils of excess cable are not usually permitted).

All cables must be continuous from source to destination, except where connectors are required for change of type, or removal of a device. Where a join is required, these must be clearly shown on the drawings submitted for approval.

All cables will be routed and terminated so that there is no undue stress on the connector. Cables to monitors shall be long enough to allow for the full range of movement of the monitor bracket without becoming taut. A suitable, neatly stored cable loop should be in place within the rack to enable it be removed from the lectern for servicing.

The use of IR control systems should be avoided in preference for RS-232 or other cabled control standards. Use of IR control must be agreed in advance with IS. All user facing cables are to be labelled in a clear and unambiguous professional manner, facilitating the ease of their use by non-technical users. And be of the pre-moulded type where possible

Connection Plate Requirements

Connection plate details must be approved with IS before manufacture and be of a standard used in all central teaching rooms. All connectors on any connection plate or device shall be functional, no dummy connectors are permitted. Where no connection is required, blanking plates should be used.

Connection plates shall be consistent throughout a project and schools/departments undertaking their own projects with IS to ensure a standard, consistent approach is can be followed.

Connectors shall be securely fitted with fixing screws, anti-rotate mechanisms, or locking latches as appropriate.

Containment

Electrical and data containment will be provided by the main electrical contractor.

Where containment is the responsibility of the AV contractor it will: Be contained, no cable runs across open floor are permitted. Be securely fixed, no self-adhesive trunking is permitted. Match existing containment, be straight, level and free from unnecessary joins.



All cabling must be run in appropriately sized conduit to allow for future replacement, addition or upgrade of cables. All entry and exit points to/from containment, including entry/exit directly from walls will be appropriate, tidy and installed in a safe manner.

Where floor boxes are used, wiring should be such that boxes can be shut allowing sufficient room for any cables to turn and exit the box without strain. This will normally necessitate the use of right angle connectors. Floor boxes must be at least three compartments, along, where possible, with the containment that feeds them. One compartment shall be for AV cabling, one for power, and one for network cabling.

Where dado level trunking is used this should also have separate compartments carrying AV cables, networking and power cables. When an umbilical sleeve is used to attach to the AV equipment/lectern it must be protected by appropriate braiding and secured by a retaining wire, shorter than the length of AV cables in order to prevent damage.

Power and Data Services

All teaching spaces will require at least 4, ideally 6 data sockets which should be grouped around the main teaching or lectern area. All teaching spaces will require at least 2 double sockets inside the lectern and double socket fitted external to the lectern. 1 x double socket per projection point.

Drawings

Drawings will usually be submitted electronically in CAD (.dwg) and/or Portable Format (.pdf) On major building projects, system schematic, cable schedule & equipment installation layout drawings are required at the following stages: Approval – minimum 2 weeks before rack build or on-site installation begins. Construction As Built

Where multiple rooms have the same equipment or layout, a generic drawing set may be used to cover all rooms, for the first 2 stages with final As Built drawings showing all alterations and amendments from the standard type.

All “as built” drawings shall show University room numbers, not any interim or architect’s room numbers. All drawings will be dated, and carry a unique reference/revision number.

Drawing styles (numbering schemes, colours, fonts, layout, etc) and connection layouts (e.g. PC always on input 1, laptop always input 2 etc) will be consistent throughout a project.



Rack Building

Equipment which is not designed to be rack-mounted should be Velcro mounted on a suitable rack-mount shelf, along with any associated low-voltage power supplies. Equipment and power supplies must not be left lying in the bottom of any rack, or in contact with any cables.

Power supplies, converter boxes, etc. should be labelled with their function or signal.

Pozi-Drive bolts should normally be used for securing equipment into racks, unless other bolts are required for security purposes.

All electrical installations must only be installed by E&FM approved contractor. Any parts of enclosures containing mains wiring must be securely fastened closed. Any power distribution within a lectern shall be installed in accordance with the current IEEE electrical wiring regulations; daisy-chaining of extension leads or power distribution is not permitted. Racks shall be earthed & bonded according to the appropriate standards.

Assistive Hearing Systems

Induction loops are preferred over infra-red systems. (This is based on feedback from the deaf community who generally dislike any systems which obviously tag them as hearing impaired.)

Induction loops will be designed and installed by an appropriately qualified engineer in accordance with BS 7594:2011 and an installation certificate issued when the system has been tested and commissioned. There will need be full integration in to the installed AV system within the room, so it’s the task should be undertaken under to management of the AV installer.

The design of the loop will be a single loop of metallic tape installed at floor level around the perimeter of the room. It is preferred that induction loops are not installed in adjacent spaces but where this is unavoidable; the adjacent systems must incorporate anti-spill features.

The University will not accept handover of an induction system until any floor coverings have been fully laid and the system tested to ensure the induction tape remains free from damage.

Fixtures and Fittings

All fixings made will be neat and tidy, made in approved locations only and will utilise a professional standard solution (no bespoke fixtures will be approved). Hardware for supporting ceiling mounts will be fixed securely at both sides of the mounting plate, no cantilever style arrangements are permitted. If



equipment locations are changes the University requires the AV contractor to make good any subsequent holes to the same surface finish as the surrounding area.

Commissioning and Handover

The AV contractor will test and commission all elements of the system (including software and configurations) with a technical representative of the University present at the time and provide a sign off sheet listing the tests carried out, before the system can be signed as complete and handed over formally.

Testing must confirm as a minimum; All signal paths as working. Audio signals are on correctly identified channel IDs which are free from hum, hiss and buzz. Video signals are be free from reflections & noise, and maintain the correct aspect ratio.

Any faults found will be the responsibility of the AV contractor to rectify before handover takes place.

There should be an appropriate amount of system documentation presented as part of the handover which should include the following as a minimum;

An equipment schedule, detailing the warranty period applicable to each item. System configuration drawings showing any subsequent amendments. Any relevant manufacturer’s manuals if paper copies are available.

Network Configuration

All network devices should have appropriate security enabled before they are connected to the University network.

In any case where network devices require usernames and passwords the contractor will change the username and password to one supplied by the University. The contractor will also supply the default usernames and passwords for the device as shipped.

No local network switches or wireless devices are to be installed without prior permission. All devices must be connected to University network outlets and clearly labelled at both ends as being connected to the relevant AV system.

Software Configurations

Any code or software required to complete the project will become the property of the University and will be supplied in a suitable and complete form at the



end of the project. This will normally consist of compiled and uncompiled versions. It will also be stored on the device where this is supported.

Any configurations, drivers, firmware and any other software required to restore or change the functionality of supplied equipment must be provided to the University in electronic format at the end of the project. All code, configurations and software must be supplied in an editable, password free state suitable for further development and shall be provided promptly at any point during the project at the University’s request.

Code will be produced as necessary to meet the software specifications as provided by the University for the project. It must also provide all reasonably expectable functionality of the installed equipment. If these conditions cause conflict, written guidance must be sought from the University. All code will be produced by a suitably qualified and experienced person. Evidence of this will be supplied to the University upon request.

Security

Projectors should be secured to a suitable structural anchor point with a padlocked steel security cable. The lectern should be designed in such a way as to prevent equipment theft, vandalism or tampering by unauthorised parties.

Security keys are any keys supplied with lecterns, monitor arms, security cables, etc. and shall be stored by the contractor at all times until handover. Keys must not be provided to anyone outside of the University.

All security keys should be accounted for at the handover stage, and key numbers listed on the room handover sheets. Any missing security keys will be replaced at the contractors’ expense. If master/suited keys are mislaid, the contractor will be required to replace all locks at the University that use that key, as their security will have been compromised.

Accessories

At handover the contractor will provide all the accessories that were supplied with the equipment and all tools provided for adjustment. No accessories are to be left in rooms. The contractor may provide electronic (.pdf or .docx) versions of operating manuals for each model of equipment used in the project.

Display Systems

Where wall space and room size permits, our standard installation will usually consist of two display systems side by side on the main teaching wall. These will be capable of independent content streams.



All display systems must satisfy the standards of visual acuity for 20/20 vision. The following examples offer some general guidance based on current specifications:

Resolution Aspect ratio View distance to screen height

XGA (1024 x 768) Standard definition data projection

4:3 5:1

HD720 (1280x720) High definition television

16:9 5:1

WXGA (1280x800) Widescreen data projector & monitor

16:10 4:1

WSXGA+ (1680x1050) Widescreen data projector & monitor

16:10 3:1

HD1080 (1920x1080) High definition television

16:9 3:1

Where visual acuity can’t be maintained from the display systems on the main teaching wall, repeater screens should be installed in appropriate locations throughout the room.

In flat floor spaces the bottom edge of display screens will usually be installed at least 1.3m above floor level. This is the typical height of a seated person and is required to ensure that people beyond the first two rows have an unobstructed view of the screen.

In raked spaces the bottom edge of the display screen may be lower than 1.3m and will be determined by the angle of rake.

Compliance with the minimum height clearances above will place even the smallest models of interactive whiteboard beyond the functional reach of a typical adult. This makes these boards unsuitable for any flat floor space in which more than two rows of adults will be conventionally seated. An interactive display screen should be used instead. Large screen monitors (up to 60” diagonal) are currently unsuitable for viewing distances beyond 2.5m at HD1080 resolution. Projectors should be used instead.

All display systems must have brightness levels and contrast ratios suitable for the screen size and ambient lighting conditions. The following examples offer some general guidance based on our current specifications.



Projector brightness Recommended use Less than 2,000 lumens Small rooms with no

ambient light Limited portable applications

2,000 to 3,000 lumens Small rooms with some ambient light Medium rooms with no ambient light

3,000 to 6,000 lumens Medium rooms with some ambient light Large rooms with no ambient light

5,000 to 10,000 lumens Large rooms with some ambient light Large rooms with long throws

Over 10,000 lumens Auditoriums Reductions in ambient light levels should be considered in preference to brighter projectors.

Projectors should be installed in a manner which minimises the amount of keystone correction required and shall be set up central to, and to fill, the entire projection screen.

Line of sight must be unobstructed between the main teaching wall and every reasonable seating position in the room. If this is not possible, repeater screens should be installed in appropriate locations throughout the room.

The Control of Artificial Optical Radiation at Work Regulations 2010 requires projection systems to be specified and installed in a manner which does not compel users to look directly into the light beam. This may necessitate the use of short-throw lenses or the placement of projection screens above head height. Short throw lenses are currently unsuitable for screen heights beyond 1.5m and viewing distances beyond 7m at WXGA resolution.

To ensure rapid and safe access for projector maintenance, projectors must be mounted where they can be easily accessed using a standard A-frame ladder. This may necessitate the use of long-throw lenses or projector lifts.

Projection screens installed above head height will usually be fixed frame and those installed below head height will usually be manual retractable. Screens used with short throw projectors will usually be tab-tensioned, retractable. Projection screens installed below head height should be installed in positions which enable simultaneous access to writing surfaces (whiteboards).



Where a screen is being installed in front of a 7.1 surround sound system, the screen should be a perforated sound screen.

Audio Systems

Audio systems should have sufficient power and speaker placements to ensure all audio content is heard clearly throughout the space.

Programme sound consists of the audio outputs of all source devices, such as computers and video players. This can be either mono or stereo but will usually be stereo by default.

Surround sound is installed where there is an intention to play cinematic content. This should use a Dolby 7.1 channel processor with appropriately matched amplification and speaker components.

Voice reinforcement is the amplification of the presenter’s voice to maintain speech intelligibility at around 15 decibels above the ambient room noise throughout the space.

Voice reinforcement channels should typically have their own amplification and speaker circuits with levels pre-set to maximise intelligibility and minimise feedback. This offers the presenter control of the programme sound independently of the voice channel to allow commentary to be heard clearly. In all spaces where lecture capture is provided, a means of capturing the presenter’s voice must be installed.

In smaller spaces (<20 occupants) it should usually be sufficient to provide only programme sound passed through a basic amplifier and speakers. Mid-sized spaces (<100 occupants) should add a lectern microphone either into the programme sound mix or via a separate voice reinforcement channel as the preferred option. In large spaces (100+ occupants) voice reinforcement will always be provided via separate voice reinforcement channels. In addition to the lectern microphone, this system will also include at least one wearable radio microphone for the presenter. It may also include additional microphones (radio or cabled) for use by the audience or panel members.

Radio microphones should be designed to operate on UHF channels. These microphones should be configured to operate on the licence-free channel 70 unless appropriate licences have been obtained to operate on channel 38.

In any space where audience participation is a regular feature, it may be desirable to install a DSP controlled, multi-microphone array above the audience area.



Computer

All teaching spaces should have a PC which is capable of running the standard University teaching image. Power management settings will be applied via the installed image. Keyboards and mice should usually be wired and captive to prevent removal. Wireless keyboards and mice should only be used with approval from Information Services. Access to the PC’s USB ports shall be via extension ports on the lectern or other system furniture.

Multimedia Playback

Where DVD players are installed they should be configured to play discs from any region. The VHS format is obsolete and no longer formally supported. Where existing VHS players are installed they will remain until they cease to function, at which point they will not be replaced.

Visualizer (Document Camera)

The visualizer should have a native resolution which includes WXGA, should be capable of displaying legacy OHP materials on acetate sheets and standard user controls should include zoom, auto-focus and auto-exposure. It should be possible to position the camera head in a range of positions around the displayed object. As a minimum the camera head should move through an arc of 90 degrees from the display surface.

Overhead (acetate sheet) projectors (OHPs) are obsolete and no longer supported. Their use is restricted in response to the Control of Artificial Optical Radiation at Work Regulations 2010. Departments which maintain functional OHP units are advised that where these find their way into centrally managed teaching spaces, they will be removed and disposed of.

Auxiliary Inputs

Auxiliary inputs should be mounted on suitable connection plates and be clearly marked as to their function and should be installed in a location and manner which is easily accessible to users, preferably on or directly adjacent to the main operating surface of the system furniture.

The following auxiliary inputs and associated connection cables will be provided:

Analogue laptop (VGA) Stereo analogue laptop audio (3.5mm TRS) Stereo analogue audio (RCA) Digital video and audio for laptop and auxiliary video devices (HDMI) USB x 2 (Access to PC USB inputs)



Signal Processing

A video signal switcher/scaler should be installed which enables all system inputs to be switched to either single or multiple output streams, depending on the room type. The switcher/scaler should support the full bandwidth of all connected devices and pass any relevant EDID or HDCP data streams. An audio signal switcher/mixer should be installed which enables all system inputs to be switched to either a single audio output or separate programme and voice reinforcement channels, depending on the room type. The switcher/mixer should also support a minimum of two microphone inputs with phantom power and have basic DSP functionality.

The video and audio switcher functions may be incorporated into one device. Signal processing functions may also be incorporated into an integrated control system processor.

Control System

All devices connected to the control system must have a full control API available. Where available, model specific control system modules should be used. Where model specific control system modules are not available, full control modules for each device will need to be written by a suitably qualified programmer. Controls should be logically grouped, standardised in style and layout in all rooms throughout the campus. The system should provide remote support functionality.

System Furniture

System equipment should be contained in secure, well ventilated furniture to prevent removal, tampering and unauthorised access. User accessible controls and auxiliary connection points should be readily available to the user as they face the audience. System furniture should enable compliance with current DDA regulations. A lectern should provide sufficient flat space for at least two sheets of A4 paper or a laptop, in addition to the operational panels, keyboard and mouse (and space to operate these comfortably). In larger rooms a demo bench may also be provided adjacent to the lectern.

Acoustic and Lighting

The British standard for reverberation time in teaching spaces is 0.6 seconds. The British standard for background noise in teaching spaces is 35 dBA.

Reverberation time and background noise levels in excess of these figures will reduce speech intelligibility. Therefore remedial work should be undertaken to correct the acoustic deficiencies.



All lighting must be controllable such as to avoid light spill onto projection screens. This is usually achieved by placing all lighting adjacent to the projection screen on a separate, controllable circuit. Where there is no physical overlap between projection screen and writing surfaces, it may be desirable to have task lighting focused on the writing surface to enable it to be seen clearly when other lighting is dimmed. There must be no spill from this lighting onto the projection screen.

Where lighting is dimmed to satisfy the requirements above, it must be configured to allow student note-taking under projection conditions.

Illumination of the lecturer’s notes can usually be achieved by a directional task light attached to the lectern.

References

Lancaster University, Campus AV Specification (2011)

Providing Teaching Room Services – Good Practice and Standards. A Report by the Lecture Theatre Services Managers Group for JISC ASSIST (1999)

SCHOMS Benchmarking report (2010)

University of Hull, AV Guidelines (2012)

IEC 60574-21 International Specification for audio visual, video and television equipment systems.

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