Glossary

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A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q | R | S | T | U | V | W | X | Y | Z

4:3 - the aspect ratio of a standard TV screen. For every four horizontal units there are three vertical ones, so a screen 16 inches wide will be 12 inches high.

5.1 - the number of channels of audio reproduction used by surround sound formats such as Dolby Digital and DTS. The 5.1 channels comprise front left, front right, front centre, surround left, surround right and a dedicated Low Frequency Effects (bass) channel, represented by the '.1.' Audio reproduction in 5.1 surround is found on DVDs, DVD-Audio, digital television, and digital movie soundtracks.

6.1 - the number of channel used by the DTS ES sound format. It is similar to 5.1 but also includes a dedicated, discrete centre-surround channel.

16:9 - the aspect ratio of a widescreen TV. For every sixteen horizontal units there are nine vertical ones, so a screen 24 inches wide will be 13.5 inches high.

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A

ADSL - Asymmetric Digital Subscriber Line. ADSL uses existing copper wire telephone lines to provide high-speed (or broadband) data transfer. It is asymmetric because the downstream (towards the customer) data rates tend to be faster than upstream (towards the network) rates. In theory, ADSL supports up to 9Mb/s downstream and 640kb/s upstream, compared with ISDN that supports 128kb/s downstream and upstream. ADSL operates alongside the existing telephone service, and so supports Internet use as well as a normal telephone line for example.

AOD - Advanced Optical Disc. Created by Toshiba in conjunction with NEC, the AOD format is a more recent development than the Blu-Ray Disc format, but is supported by the DVD Forum - a consortium that includes all nine members of the 'Blu-Ray Disc Founders' (see Blu-Ray Disc Format). The AOD format uses blue laser technology to store up to 15GB of data on a single-layered read-only 12cm optical disc. A dual-layered disc would hold 30GB, and a rewriteable version would hold 20GB. AOD is expected to offer long recording times by using MPEG-4 compression, which uses less data than MPEG-2.

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B

Balun - a device that converts a balanced line signal to an unbalanced one, and vice versa. A balun is typically used for converting an unbalanced television antenna signal, with one conductor and an electrical earth, to a balanced signal with two conductors having equal currents that are opposite in phase.

Bandwidth - the band of frequencies occupied by transmitted modulated signals, but also used to refer to the capacity available in a communications network.

BACS - Building Automation and Control Systems.

BEMS - Building Energy Management Systems

Blu-Ray Disc Format - a format developed by the 'Blu-Ray Disc Founders,' namely Hitachi, LG Electronics, Matsushita, Pioneer, Philips, Samsung, Sharp, Sony, and Thomson. This uses a new blue-violet laser technology that has a smaller laser beam width than a conventional laser beam and so can store more data on a standard 12cm optical disc. A single-layered Blu-Ray Disc can store up to 27GB, and a dual-layered double-sided Blu-Ray Disc can store up to 54GB.

Broadband - generally defined as a connection that offers data rates of more than 128kb/s.

Bus - an electrical transmission path that usually comprises one or more conductors, whereby all attached devices receive all transmissions along the bus, at the same time.

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C

Category 5 - (a.k.a. Cat5) a four-pair, twisted, telephone-style cable that is used to carry telephone and data signals at rates of up to 100Mb/s.

Category 6 - (a.k.a. Cat6 ) a four-pair, twisted, telephone-style cable with a longitudinal separator to ensure that each pair is kept a minimum distance from its neighbour. It supports more than double the bandwidth of Cat5, but requires a higher standard of installation.

CATV - Abbreviation for cable TV.

CCTV - Closed-Circuit Television.

Coaxial Cable (a.k.a. coax) - a cable that has a single centre copper conductor surrounded by an insulating material that is covered with another conductive material, usually a braid or shield, and then wrapped in an overall jacket. Coaxial cable is typically used for video distribution of TV, satellite, video and CCTV images. Coaxial cables are designated by their overall impedance, but the naming process bears no relation to this. For example RG-58 cable has an impedance of 50 ohms, while RG-62 has an impedance of 93 ohms.

CRT - Cathode Ray Tube. The technology used in conventional television sets, where the picture is formed on a glass picture tube by an electron gun that excites phosphors on the back of the screen glass. CRT technology offers the most absolute levels of black as there is no light spill, and offers a large dynamic range, producing high peak in brightness over a short period. CRT technology is also used in projectors.

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D

DECT- Digital European Cordless Telecommunication. DECT is a digital cordless system for communication within a local area, for example within a residence or a company.

Digital Television - (DTV) digital television theoretically offers better quality pictures than analogue because the digital signal is much less susceptible to interference. It uses MPEG-2 coding for video and audio, and once received, the digital signal is converted back to analogue via a set-top box (STB) or hardware within an integrated television set (iTV). DTV is available via satellite and cable through subscription, or free via terrestrial through a Freeview box. DTV offers the broadcaster the possibility of more channels, as well as interactive services.

Disc - the conventional spelling used for an optical disc, such as a CD or DVD.

Disk - the conventional spelling used for a Winchester hard disk, a non-optical magnetic medium.

DiVX - A pay-per-view version of DVD. The disc costs less to buy than a normal DVD, but after a 48-hour viewing window has passed, the disc expires unless you pay more to extend the viewing window.

DMD - Digital Micromirror Device. See DLP.

Dolby Digital - a digital surround sound system developed by Dolby laboratories. It offers from 1 to 5.1 channels of audio reproduction: front left, front right, front centre, surround left, surround right and a dedicated Low Frequency Effects (bass) channel, represented by the '.1.' DVD players with Dolby Digital capability can provide a backward-compatible mixdown of the five main channels to four for Dolby Pro-Logic playback.

Dolby Pro-Logic (a.k.a. Dolby Surround) - a surround sound system developed by Dolby Laboratories. It offers four channels of audio reproduction: front left, front right, front centre and a mono surround channel, usually delivered by two surround speakers located behind the listening position.

DLP - Digital Light Processing - a way to project and display video signals based on the Digital Micromirror Device (DMD) developed by Texas Instruments. The DMD stores image information and reflects light with thousands of 16x16-micron mirrors, and is designed to provide noise-free, precise image quality with digital gray scale and good colour reproduction. Close spacing of the micromirrors causes video images to be projected as seamless pictures with higher perceived resolution.

DSL - Digital Subscriber Line. DSL uses existing copper wire telephone lines to provide high-speed (or broadband) data transfer. A common configuration of DSL is to support higher data rates downstream (towards the customer) and lower data rates upstream (towards the network). This arrangement is asymmetric (see ADSL). Another common configuration is symmetrical, having the same data rate in both directions.

DSLAM - a multiplexing system that must be installed at the consumer's local telephone exchange in order to support ADSL and separate voice traffic and data traffic on the telephone line.

DTS - a 5.1 digital surround sound system developed by Digital Theater Systems. It offers 5.1 channels of audio reproduction: front left, front right, front centre, surround left, surround right and a dedicated Low Frequency Effects (bass) channel, represented by the '.1.' DTS is used on CDs and DVDs, and is recommended for multichannel music playback. It uses less compression than Dolby Digital, and so requires more disc space.

DVD - Digital Versatile Disc (a.k.a. Digital Video Disc). An optical disc that has two sides and can store 4.7GB of data per side, i.e. enough for a 133-minute movie including several audio tracks in formats such as stereo, Dolby Digital or DTS, and advanced menu systems, subtitles and still pictures that can be played by many standalone DVD players and most computer DVD-ROMs. If the disc has two layers per side, then it can store up to 17GB of data. DVD uses MPEG-2 compression for video and audio.

DVD-Video. A means of distinguishing between DVD that is used primarily for audio (DVD-Audio) and DVD that is primarily used for video.

DVD-R - DVD Recordable. DVD-R is a non-rewriteable format and it is compatible with around 92% of all DVD players and most DVD-ROMs.

DVD+R - DVD Recordable. DVD+R has some different features to DVD-R, and is compatible with about 86% of all DVD players and most DVD-ROMs.

DVD-RW - DVD ReWriteable. It is compatible with about 75% of all DVD players and most DVD-ROMs. DVD-RW supports single-sided 4.7GB DVDs(called DVD-5) and double-sided 9.4GB DVDs(called DVD-10).

DVD+RW - DVD ReWriteable. DVD+RW as some different features to DVD-RW and is compatible with about 75% of all DVD players and most DVD-ROMs.

DVD-RAM - a recordable DVD format that is claimed to have the best recording features, but which is not compatible with most DVD-ROM drives and DVD-Video players. It is more commonly used in applications where a removable hard disk might be used.

DVD-Audio - a Digital Versatile Disc that offers audio quality higher than standard compact disc. It supports 24-bit/192kHz stereo audio, and 24-bit/96kHz 5.1 channel PCM playback capability. DVD-Audio discs will play at their highest quality on DVD-Audio-compatible players. A DVD-Audio disc can also be played on a standard DVD player for multichannel sound, albeit at DVD-Video quality.

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E

EIB - European Installation Bus (a.k.a. Instabus). An embedded control protocol for digital communication between devices. It consists of a two-wire bus line that is installed along with normal electrical wiring. The Instabus functions like a telephone line over which appliances can be controlled, and links all appliances to a decentralised communication system.

EMI - Electromagnetic interference. EMI is generated by the internal circuits of devices such as personal computers, wireless devices and CRT displays, and can cause interference and disruption of other electronic devices such as cordless telephones, home entertainment systems, computers, and certain medical devices. There are regulations governing EMI by electronic equipment in Europe, and problems can be minimised by grounding, filtering and shielding.

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F

FEXT - Far End Cross Talk.

FireWire - see IEEE-1394.

Front Projection - when a projector, usually ceiling-mounted, projects the picture onto a white screen. Both the projector and the screen may be retractable when not in use.

FVD - Forward Versatile Disc. An optical disc format for storing high definition video based on red laser technology, developed by Taiwan's Advanced Optical Storage Research Alliance (AOSRA) in conjunction with the Industrial Technology Research Institute (ITRI).

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H

HAVi - Home Audio Video Interoperability. An initiative by some major consumer electronics companies to network consumer electronics hardware using an IEEE1394 connection. The network does not require a dedicated PC, and would allow communication with devices, such as heating, lighting and home appliances, operating on other networks.

HDCD - high-definition-compatible digital. An enhancement to standard audio CDs that effectively increases the 16-bit dynamic range to 20-bits. Originally developed by Pacific Microsonics, the technology is now owned by Microsoft. HDCDs are compatible with non-HDCD players, and standard CDs can be played on HDCD players.

Home automation - the automatic control of systems such as heating, lighting, entertainment, security and communications by a single user interface. Operation might be by remote control, wall-mounted keypad and/or personal computer, and may be manual or programmed.

Hub/Switch - a device for connecting computers and peripherals to a router. A router connects a home network to outside networks or computers, while a hub or switch connects the computers and peripherals within the house, and appropriately disseminates the information they request. Routers and hubs/switches are traditionally separate units, but are more frequently being bundled in packages that include a built-in hub/switch, and sometimes a DSL modem also.

HVAC - Heating, Ventilation and Air-Conditioning.

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I

IEEE1394 - (a.k.a. FireWire or iLink). A communications protocol that allows direct digital transfer of data from one device to another. IEEE1394 allows for example, digital video from a DV camcorder to be transferred to the hard disk of a personal computer, provided both camera and computer have each have an IEEE1394 connection. IEEE1394 is also at the heart of the HAVi home networking standard (see HAVi).

IEEE802.11 - a wireless transmission protocol. It exists in a number of versions (labelled a to g) that run at different frequencies in the spectrum 2.4GHz (g) to 5.7GHz (a), giving different possible data rates. Version b is currently in commercial use, predominately for wireless PC networks (WLAN).

IR - Infra-red. IR frequencies have electromagnetic wavelengths that are shorter than those of RF fields. IR is typically used for sending wireless control signals from television and hi-fi remote-controllers, some cordless computer keyboards and mice, and some wireless hi-fi headphones.

ISDN - Integrated Services Digital Network. A communications network offered by BT for data transmission of 64kb/s per channel. ISDN has mostly been superseded by broadband/ADSL.

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K

kb/s - (a.k.a. kbps) kilobits per second.

kB/s - (a.k.a. kBps) kilobytes per second. There 8 bits to a byte.

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L

Last mile - colloquial name for the final part of the communications signal chain, running between the local exchange and individual buildings.

LCD - Liquid Crystal Display. A digital display that uses liquid crystal cells that change reflectivity in an applied electric field. LCDs are used for portable computer displays, watches and some TV screens.

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M

Macro - a sequence of commands that have been pre-programmed into a control device, and that can be activated by one touch. For example, when the user selects 'Showtime' on a home cinema touchscreen remote control, it could be programmed to dim the lights, draw the blinds, lower the projector screen, start up the DVD player, amplifier and projector and commence playback.

M&E - Mechanical and Electrical services.

Mb/s - (a.k.a. Mbps) megabits per second. 1Mb/s is 1024 times faster than 1kb/s.

MB/s - (a.k.a. MBps) megabytes per second.

MDU - Multiple Domestic Unit.

MP3 - MPEG Layer 3. The data required for an MP3-encoded audio track is 12 times less than that of the same track recorded at standard CD quality. Hence MP3 requires shorter download times if used to transfer music via the Internet for example, and less storage space, giving rise to a proliferation of solid-state MP3 players such as the Apple iPod and players in mobile phones. MP3 files can be stored on any digital recording medium. Provided they have MP3 decoding capabilities, CD and DVD players can read a CD that has been burned with MP3 tracks.

MPEG-2 - developed by the Motion Pictures Experts Group (MPEG), MPEG-2 is a video compression algorithm that compresses the data required to represent a video picture by a factor of around 40. MPEG-2 is used by DVD-Video, digital broadcast satellite, and digital TV (including HDTV).

MPEG-4 - sometimes called the 'MP3 of the video world', MPEG-4 is designed for multimedia applications including web, handheld and wireless devices. It is based on object-based compression, whereby individual objects within a scene are tracked separately and compressed together to create an MPEG-4 file. This results in very efficient compression that is highly scalable, from low bit rates to high quality.

Multiroom - a term used to describe any distributed system, such as an audio or heating system, that covers a number of rooms in a building.

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N

NEXT - Near End Cross Talk.

NVOD - Near Video On Demand. A system typically used for subscription movies, whereby the same movie is continuously played on several channels, with the start time between each channel being staggered by 15 or 30 minutes, so that the consumer does not have too long a wait to catch the beginning.

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P

Plasma display - a display that produces an image by using a matrix of transparent electrodes, positioned in front of a gas- (plasma) filled cavity. The gas is contained in hundreds of thousands of tiny cells between the two plates, and when excited by the electrodes, acts like tiny fluorescent lights. Each pixel of the image comprises a red fluorescent light, a green one and a blue one. Just like a CRT television, the plasma display varies the intensities of the different lights to produce a full range of colours. Most plasma displays are not technically televisions, since they do not include a television tuner. They must be connected to a tuner, cable box or some other source such as a DVD or VCR. Plasma displays are popular because even large-screen models are only a few inches thick.

PDA - Personal Digital Assistant.

PLC - Power Line Carrier or Power Line Communication. The use of a residence's existing mains wiring as a network that also carries control information and/or content.

PVR - Personal Video Recorder. A video recorder that records to hard disk, and usually supports both programmed recording as well as automated recording according to your personal profile.

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R

Rear Projection Television - a large-screen television which uses a projector to fire the image onto a perspex screen, all housed in one self-contained unit. Rear projection TVs are said to give the best picture quality of all, but have traditionally had the disadvantage of being quite deep, although relatively shallow models are emerging.

Regional Coding - a system used to prevent DVDs bought in one region of the world from being played in another in order to protect revenues form theatrical movie screenings. The world is divided into six regions, including the USA & Canada (Region 1) and Europe & Japan (Region 2). There is also a region-free designation, Region 0. In practice, Regional Codes can often be side-stepped by DVD players.

REN - Ringer Equivalency Number. Usually, the total number of ringer equivalency phone equipment (such as telephone base units and answering machines) attached to a domestic network cannot exceed three, otherwise there may not be sufficient current to make the devices ring. The REN value is usually printed on the bottom of a unit , and in the unit's manual.

Router - A router connects the home network and outside networks or computers, while a hub or switch connects the computers and peripherals within the house and appropriately disseminates the information they request. Routers and hubs/switches are traditionally separate units, but are more frequently being 'bundled' in packages that include a built-in hub/switch, and sometimes a DSL modem also.

RF - Radio Frequency. Many types of wireless system, such as cordless and mobile phones, radio and television signals, and satellite communications, operate in the RF spectrum.

RF Modulator - a device which converts a line-level signal into a robust radio frequency signal for wireless or wired transmission.

RG-6 Quad Shield - coaxial cable with an impedance of 75 ohms. It is recommended for CATV residential applications, and can handle CATV, satellite, HDTV and cable modems, with some additional shielding to prevent noise.

RJ-45 - a serial connector used with Ethernet and Token Ring devices that looks like a telephone jack but has eight wires instead of four or six.

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S

SACD - Super Audio CD. SACD offers better-quality audio than a CD, and supports both stereo and multichannel audio. SACD can be played on SACD players, as well as on SACD-compatible players such as certain DVD-Video players. Hybrid SACD discs contain two versions of the recording. One version plays on the latest generation of SACD hardware, and the other plays on standard home, car or portable CD players. SACD uses a technology called Direct Stream Digital (DSD) to record and replay audio. While standard CD audio uses 16-bit words sampled 44,100 times a second, DSD stores data as a stream of single bits sampled at 2.8224MHz. SACD players may play standard CDs, but SACD discs do not always play on standard CD players.

Scene Lighting - where different lighting circuits are dimmed or activated to create a particular mood, such as a reading scene or movie-viewing scene.

SDH - Synchronous Digital Hierarchy. An international digital telecommunications network hierarchy that standardises transmission around the bit rate of 51.84Mb/s and multiples thereof. SDH specifies how data is transported across optical fibre transmission links, and supports transmission speeds of up to 10GB/s.

Smart home - a dwelling, usually a new one, that is equipped with special structured wiring that allows occupants to remotely control or program various automated home electronic devices using single commands. For example, on leaving the home, one button press can set the alarm, check and lock all the windows and external doors and activate a light switching program. On holiday, the homeowner could use a touchtone phone to control temperature gauges, switch appliances on or off, program a home cinema or entertainment system, and perform various other tasks.

SONET - Synchronous Optical Network. The American version of SDH.

Star/Radial Wiring - (a.k.a. Home Run). A wiring system whereby cables are distributed from a central controller hub to each access point, allowing independent access to any of the signals or services from any point in the house.

Surround Sound - a general term for audio reproduction that is not only from the traditional front left and right positions, but from behind and possibly to the side of the listener. A number of configurations are in use, typically ranging from 4 channels (front left, centre and right, and one rear channel fed to two speakers at the back left and right); the popular 5.1 (front left, centre and right, back and right surrounds, and a low frequency effects (.1) channel); 7.1 (5.1 plus side left and right), and even 10.2 (additional side channels and a second .1 channel).

Subwoofer - (a.k.a. sub). A loudspeaker that is specifically designed to handle bass in a home system. It should not be confused with the low frequency effects (LFE) channel (or .1 channel) of surround formats. When audio channels from a disc enter a surround processor, the processor's bass management system filters the low frequencies out of the feeds to speakers that cannot handle them, and feeds them to loudspeakers that can - either large, full-range speakers, or the subwoofer, or both.

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T

TFT - Thin Film Transistor. The highest quality and brightest LCD colour display type. A method for packaging one to four transistors per pixel within a flexible material that is the same size and shape as the LCD display, so that the transistors for each pixel lie directly behind the liquid crystal cells that they control.

THX - Tomlinson Holman's eXperiment. An audio standard developed by Lucasfilm for some categories of consumer electronic hardware such as home cinema amplifiers, speakers and source equipment. Equipment must meet stringent THX specifications in order to gain THX status.

Touchscreen - a touch-sensitive screen that allows the user to activate graphical buttons and access menus, simply by touching the screen. In home entertainment and automation, the touchscreen, in the form of a touch-sensitive LCD, tends to be incorporated into remote controllers that allow the user to select different menus and controls.

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U

UMTS - Universal Mobile Telecommunications System. The standard adopted for third generation (3G) mobile networks for the UK and most of the world.

UpnP Universal Plug and Play. Developed by Microsoft, this is an open standard technology for transparently connecting appliances, PCs, and services, by extending Plug and Play to support networks and peer-to-peer discovery and configuration.

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V

VC - Video Conferencing.

VCR - Video Cassette Recorder.

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W

Wi-Fi - Wireless Fidelity. Wi-Fi is the popular term for a high-frequency wireless local area network (WLAN). It is specified in the IEEE 802.11b specification and is part of a series of wireless specifications together with 802.11, 802.11a, and 802.11g. In many cases, Wi-Fi is more convenient than a wired LAN, but unless adequately protected, a Wi-Fi LAN can be susceptible to access from the outside by unauthorised users, some of whom use the access as a free Internet connection. (The activity of locating and exploiting security-exposed wireless LANs is commonly known as 'war driving' and an identifying iconography has developed that is known as 'warchalking.')

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X

X-10 - a communications language that allows compatible products to talk to each other using the existing electrical wiring in the home. A technology known as Powerline Carrier System (PCS) is used to send coded signals along a home's existing electric wiring to programmable switches, or outlets. These signals convey commands to specific 'addresses' or devices. A PCS transmitter, for instance, can send a signal along a home's wiring, and a receiver plugged into any electric outlet in the home could receive that signal and operate the appliance to which it is attached. A common protocol for PCS is known as X10. X10 signals use short RF bursts to represent digital information for communication between transmitters and receivers.

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Z

Zone - a designated area of a building for the provision of any service. In a multi-room audio system, for example, each bedroom would typically constitute a separate zone.

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