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Amplifier

Boosts signals to drive speakers. Can be one-box (integrated) or have separate pre and power sections.

Anamorphic

Anamorphically enhanced DVD discs have been coded to offer improved picture quality on widescreen TV sets and banish most, if not all of, the letterbox effect, too.

Bass reflex

A speaker design using air-flow from a port in the cabinet to help low frequencies.

Component video

Connection system - usually between DVD player and display device such as TV or projector - in which the three colour signals, red, blue and green, are each carried by their own cable. Connections usually on a trio of phono sockets or BNC connectors

Composite video

A single connection, for example between a DVD player and a TV - in which the whole picture signal is carried. Usually on a single phono socket, generally coloured yellow to distinguish it from the other connections provided.

DAC

Digital-to-analogue converter, turning on/off pulses into analogue sound. CD players have DACs built in. Separate DACs can upgrade a CDplayer or other digital player/ recorder, or can be used with dedicated CD transports.

Digital output

Allows the digital signal to be recorded or processed by an offboard DAC. Electrical or optical (fibre optic) outputs are provided.

DLP (Digital Light Processing)

Digital Light Processing is an astonishingly sophisticated system for generating projected images. The core of the system is the DMD, or Digital MicroMirror Device. This tiny microprocessor- controlled chip is composed of over 1.3 million individual mirrors, each hinged and able to tilt +10 or -10 degrees. A powerful lamp shines on to the surface of the mirror through a rotating colour wheel composed of the three primary colours (Red, Green, Blue). By individually tilting each micromirror, the DLP unit can either reflect appropriately coloured light out through the projection lens to create a dot of screen detail a pixel or send it into a light-absorbing light creating dark pixels.

Dolby Digital

Also known as AC-3, this is the latest home cinema sound system from Dolby, using five discrete channels of digital sound plus a separate subwoofer channel

Dolby Digital Surround EX

Development of Dolby Digital 5.1 surround audio that includes a matrixed centre-rear audio signal to provide additional surround envelopment. Requires a suitable decoder, with amplification, and either one or two additional centre rear speakers.

Dolby Pro-Logic II

Enhanced version of the original Pro-Logic, with improved channel steering for an effect closer to that available from true Dolby Digital source material. Also capable of extremely good effects with stereo material when using the Music mode

DTS

Discrete-channel home cinema digital sound system - rival to Dolby Digital

DTS ES Discrete 6.1

The only 'true' 6.1 system, with an entirely discrete digital channel providing centre-rear channel effects. Requires a dedicated decoder.

DVD

Video Designed for home entertainment, they play on consumer DVD players that plug into TV sets, or on desktop PCs equipped with a DVD-ROM drive and the requisite hardware/software.

DVD Audio

The standard is based around 24 bit/96kHz sampling. Some audio-only discs have already been produced using the DVD Video standard.

HDMI

High-Definition Multimedia Interface. A digital interface able to carry video, audio, data, and control signals. Typically used between DVD players and TV displays, it's also supported on some AV receivers, which provide HDMI switching. How much data it carries is down to implementation - the original version just carries video and stereo audio, while the latest is able to carry high-resolution multichannel audio in digital form as well as video.

Impedance

Electrical property. A low impedance draws a high current flow from the source, while a high impedance draws a little. This means that speakers with a low impedance (lower than 6-8ohms) are more difficult for an amplifier to drive.

Line level

Describes inputs to amplifiers which don't need amplifying before the amp can use them.

MP3

MPEG 1, layer 3. The compression system used for downloading music files from the Internet to a PC or MP3 recording device. It reduces file sizes by a factor of 12 to enable faster downloads, but it's possible to code music at a number of data rates, from pretty good to definitely lo-fi.

Ohm

Unit of resistance to current. Impedance of a speaker is measured in ohms - generally the lower the figure the harder it is to drive.

Power handling

The maximum safe power for speakers. But be aware that it's easier to damage speakers with an amp of too low power driven hard, than with too much power.

Progressive Scan

Conventional TV pictures are made up of two fields, each one comprising alternate lines of the 625 used to make up a PAL TV picture or the 525 used in NTSC. Your eye is fooled into seeing a whole picture by the speed of the scanning. Progressive scan improves picture quality by scanning the whole field in one hit, not just half of the lines at a time, but to take advantage of this you need a video source - usually a DVD player - and a display device such as a TV or projector - capable of supporting this system. Progressive scan is currently only really relevant with NTSC signals, but work is being done to apply it to the British PAL TV system too.

RGB

Simply, Red, Green and Blue - a video connection, usually on a Scart cable - in which the three colour components of the picture are carried separately. In order to make this connection you need a DVD player and TV with RGB-enabled Scart sockets - not all older models are. You'll also need a 21-pin Scart cable that's either fully wired - ie with all 21-pins connected at ends - or, if you're running the sound from your player through your hi-fi system, at least a cable with the correct video pins hooked up. Some dedicated RGB cables only have these video connections, leaving out the other Scart capabilities in the quest for better picture.

S-video

Mini-Din plug connection used to carry video signal between source and display, in which the brightness and colour components of the signal are transmitted separately. Opinion is divided whether this or a Scart connection gives the best picture quality.

Scart

aka Euroconnector or even in some very old cases Peritel. A 21-pin connection between audio-visual components, carrying sound, vision and other signals. An RGB Scart is held by many to give the best picture quality for most people hooking up a DVD player to a TV set. Not all Scart cables are fully-wired - some have only the basic picture and sound connections made, while others are designed to carry video only. For more on this see entry under RGB.

Subwoofer

A separate woofer box to produce the deep lows smaller speakers can't reach.

THX

Developed by LucasFilm, this is basically a set of standards for Dolby Pro-Logic gear, which should guarantee a certain quality of home cinema sound. Needs electronics and speakers made to exacting specs, which tend to be pricey.

THX Surround EX

Officially-licensed decoding system for Dolby Digital Surround EX software. Mode can also be applied to DTS-ES software. Usually uses two centre-rear channel speakers.

Widescreen

More and more TV programmes, and nearly all DVD discs, are made in widescreen format. This can vary from 14:9 (a compromise ratio used by TV broadcasters) to 16:9 which is the ratio used on widescreen TV sets and most DVDs. Many films shown at the cinema are in 21:9, while conventional square TVs are 4:3.