Audio Visual Glossary Terms

4:3Aspect 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.
5.1Number 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 center, surround left, surround right and a dedicated Low-Frequency Effects (bass) channel, represented by the '.1.' Audio reproduction in 5.1 surrounds is found on DVDs, DVD-Audio, digital television, and digital movie soundtracks.
6.1Number of the channel used by the DTS ES sound format. It is similar to 5.1 but also includes a dedicated, discrete center-surround channel.
16:9Aspect 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.
ActuatorHome automation device that switches digital (on/off for an electrical switch) or analog signals, e.g., dimmer or blind control.
 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 (toward the customer) data rates tend to be faster than upstream (toward 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.
 Advanced Optical Disc (AOD)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.’ 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.
 AssociationProcess of adding a device to a group. By doing so, the device can be controlled as part of the group.
 BalunDevice 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.
 BandwidthBand of frequencies occupied by transmitted modulated signals, but also used to refer to the capacity available in a communications network.

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