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Glossary Please note that the purpose of this glossary is to clarify some of the terms commonly associated with audio/video subject matter. Many of the definitions listed below have been simplified or altered to more effectively convey their meanings in an audio/video context. 1080i1080i means that the resolution of the picture is 1920 vertical pixels by 1080 horizontal pixels and i stands for interlaced scanning. Interlaced scanning is based on the principle that the screen shows every odd line at one scan of the screen and then all the even lines in a second scan. 1080p1080p means that the resolution of the picture is 1,920 vertical pixels by 1,080 horizontal pixels and p stands again for progressive scanning. This format works on the same principle as 720p; the only difference is that in this type there are more pixels and the resolution is better. 16:916:9 is aspect ratio of movie screen and widescreen DTV formats used in all HDTV (High Definition TV) and some SDTV (Standard Definition TV); it stands for 16 arbitrary units of width for every 9 arbitrary units of height. 4:34:3 is aspect ratio of traditional squarish National Television Systems Committee (NTSC) TV screens; it stands for four arbitrary units of width for every three arbitrary units of height. 720p720p means that the resolution of the picture is 1,280 vertical pixels by 720 horizontal pixels and p stands for progressive scanning. Progressive scanning offers a smoother picture as 720 horizontal lines are scanned progressively or in succession in a vertical frame that is repeated 30 times a second. AACAdvanced Audio Coding. An audio codec used increasingly for downloaded music files, streaming-media, and satellite-radio applications. AADAnalog Analog Digital. A designation that indicates the recorded material was first recorded with analog equipment, then remixed on analog equipment and finally placed onto a digital recording medium. ACAlternating Current. The standard electrical current delivered to homes and businesses in the U.S. As opposed to DC - Direct Current. AC-3The original named used for Dolby Digital. The name was later changed to feature the Dolby name. AccuracyWhen audio or video signals pass through a component, the signal may be changed slightly. The closer the output is to the original input, the greater the accuracy of the component. Acoustic Suspension SpeakerA sealed-box speaker that uses the air behind the woofer to control cone movement. Active SpeakerA speaker which includes an integral power amplifier to power or drive the speaker. Active Scan LinesThe scan lines in a video frame that carry picture information rather than data for closed captioning or synchronization. A/DAnalog to Digital. Refers to the conversion of analog sound or video to digital during storage, manipulation, or recording. ADDAnalog Digital Digital. A designation that indicates the recorded material was first recorded with analog equipment, then remixed on digital equipment and finally placed onto a digital recording medium. Adjacent Channel SelectivityWhen tuning an FM station, the next station up or down the dial may interfere with the signal. A tuner's ability to reject those neighboring signals is measured by its selectivity. Advanced Television Systems Committee (ATSC)Advanced Television Systems Committee is responsible for establishing and developing digital television standards, as well as all 18 formats of Digital TV. ALiSAlternate Lighting of Surfaces. An HD plasma panel technology designed to optimize performance when displaying 1080i material. Alternate rows of pixels are lit, similar to interlaced scanning. The resulting picture is bright, clear and improves the smoothness of movement as well extending the life of the plasma panel. AMAmplitude Modulation. The encoding of a signal into a radio wave by modulating its amplitude (the height of the wave). As opposed to FM, frequency modulation, wherein the frequency of the wave is modulated. Amplifier (or Slave Amplifier)An audio component designed to power a pair (or multiple pairs) of speakers. Amplifiers require a line-level audio signal generally output from a preamplifier or source component, and may also be fed from the "tape-out" of a stereo receiver. AnalogWhen a signal is continuously variable, it is analog. When a signal is broken into units that are rounded to discrete values, it is digital. Analog signals contain "all of the data" but it is prone to interference and degradation. It is not possible to catch and remove all of the interference from an analog signal and so the quality declines as it travels to your TV. With a digital signal, certain values are expected. When a value is received that is not within the expected range, it can be filtered or adjusted. This ability to detect and filter or repair a digital signal makes it possible to deliver a signal to your TV that is as good as when it left the studio. AnamorphicIt is the preferred DVD format for widescreen (16:9) TVs because the image is restored to its widescreen format without any reduction in image quality. Anamorphic DVDs contain the highest level of resolution (460 to 480 lines) and thus yield the best picture quality. DVDs are often not labeled as anamorphic, so look also for the words "enhanced", " widescreen", "16:9". DVDs labeled "letterboxed" and in most cases "fullscreen" will have reduced image quality or even have some of the image edited to force it to fit a 4:3 screen. Anamorphic DVDs can be played on regular 4:3 TVs, but unless your TV or DVD player has a setting to vertically adjust the image, it will appear tall and thin. ANSI LumensA standard for measuring the brightness of a projection TV. ANSI is the organization that set the standards for measurement. The IEC is now the organization setting the standard, but manufacturers are reluctant to switch, fearing consumer confusion. AntennaA device for transmitting or receiving signals. The size and shape of antennas are determined primarily by the frequency of the signal they are designed to receive. A high gain antenna is highly focused, whereas a low gain antenna receives or transmits over a wide angle.
ArtifactsArtifacts are defined as unwanted visible effects in the picture caused by disturbances and errors in the video transmission or digital processing. Artifacts include "edge crawl" or "dot crawl" or "hanging dots" in analog pictures, and "pixelation", "contouring" or "blockiness" in digital pictures. Aspect ratioAspect ratio is ratio of width to height of a TV screen. It may be either traditional squarish 4:3 ratio of the National Television Systems Committee (NTSC) TV screen or 16:9 ratio of widescreen DTV formats for all HDTV (High Definition) and some SDTV (Standard Definition). ATSCAdvanced Television Systems Committee. The organization that set the U.S. HDTV standards. It also refers to the TV channel tuner used to tune in HD signals. Compare to the NTSC which set the standard for pre HDTV signal and the tuner that tunes analog programming.
Audio / Video Patching SystemA unit designed to allow the output of a selected A/V source to be routed to the input of another A/V component (or components) for recording, playback or dubbing purposes. AttenuateTo decrease or otherwise reduce, as in to attenuate signal noise. ATVAdvanced Television. The system and the standards defined by the ATSC. Autoformer Volume ControlA device used to control the volume output from an amplifier (or speaker selector) to a pair of speakers. Autoformers offer sound quality superior to that of L-pads or purely resistive volume control designs, while minimizing power loss and heat dissipation. Automated Switching System A device used to automatically switch line level, speaker level, or composite video signals. Usually triggered by a control voltage or signal sensing circuit. Auto-ReverseA feature that automatically reverses a tape when it reaches the end. Auto-RewindA feature that automatically rewinds a tape to its beginning when it reaches the end. A/V ReceiverAlso called a Home Theater receiver, sometimes the term "integrated" is also used. Receivers take audio signals from components such as a CD player, tape deck and phonograph, amplify it and output it to the speakers. An A/V receiver is designed to also accept video inputs, such as from a DVD player, cable box and VCR, and output the signal to a television. In most cases the video signal is not processed but simply passed through to the TV. A/V receivers, in most cases, also have Dolby and DTS decoders to play multi-channel audio. A/V InputsThe connections on any component, such as a TV, receiver or VCR that enable connection to other output devices. The inputs often take the form of RCA jacks. Audio outputsAn audio output is a connection (most often an RCA jack) on a device, such as a TV, that can be connected to a stereo or home theater system. A fixed output means the stereo is used to control the volume. A variable output means that the TV and the stereo can each control the volume.
BandwidthBandwidth, in general, means amount of information that can be carried in a given time period (usually a second). More exactly, it is a range of frequencies used for transmitting picture and sound information from transmitter to your TV. Federal Communications Commission (FCC) has allocated 6 MHz for TV broadcasters for each channel. Bit RateBit rate is measured as "bits per second" (bps) and refers to the rate at which the data is transmitted. For Digital TV, the maximum possible bit rate within the bandwidth is 19.4 Mbps while SDTV has a lower bit rate. The higher the bit rate, the more data is processed which usually results to higher picture resolution or better sound quality. ClippingThe undesirable effect on a music signal which is caused by exceeding the amplifier's (or preamplifier's) signal handling capabilities. CodecCodec is a short term for "Coder-decoder." This device is used to convert analog video and audio signals into digital format, and vice verse, it can also convert received digital signals into an analog format. CompressionCompression allows the delivery of more programs in a single channel. It is an electronic manipulation of digital data that reduces and removes redundant and/or non-critical information in the digital picture and sound without noticeably degrading picture quality. One of the compression methods is called MPEG-2. Continuous IR CommandAn IR command which is issued as long as the button is pressed and held. As an example; a "Volume Up" command is a continuous IR command and a "Play" command is a normal IR command (it only needs to be tapped). See "Normal IR Command". Convenience OutletsWall plates used in custom installations to elegantly terminate wires run through walls. Available with RCA, 5-way binding post, banana jack, or F-connector terminals. Control VoltageA term used to describe a voltage output used to activate another device. Crossover An electronic circuit consisting of either a low-pass filter, a high-pass filter, or both. Its main purpose is to determine a crossover point at which frequencies will be filtered and passed to other components (subwoofers, woofers, or tweeters for example). CRT (Cathode-Ray Tube) CRT stands for cathode-ray tube. Invented in 1897, even nowadays it is the most common display technology for televisions. The tube uses an electron beam to scan lines on the screen coated with phosphor, which glows when struck by the beam. The other display technology being used more and more often nowadays in television sets is LCD. Decibel (dB) A logarithmic unit of measure commonly used to gauge relative volume in terms of dB SPL (decibels of Sound Pressure Level). The bel is unit of measure representing the logarithmic equivalent of two powers, and a decibel equals one-tenth of a bel. Diode An electronic device that permits electrical current to flow in only one direction. The white stripe marks the cathode, or negative ( - ) terminal on the diode. Distribution Amplifier A device used to distribute the output of a single audio or video component. Used to feed the inputs of several other components without effecting the strength or quality of the original source signal. Dolby Digital (Dolby AC-3) Dolby Digital, also called Digital 5.1 or AC-3, is a five-channel surround sound system which delivers CD-quality digital audio and provides five channels of full frequency for front left, front right, center, surround left and surround right speakers, plus one channel for LFE (low frequency effect) subwoofer. It is the official audio standard for Digital TV and HDTV. DTV (Digital Television) DTV stands for Digital Television. It refers to all digital television formats and standards established by the Advanced Television Systems Committee (ATSC). Two basic DTV standards are HDTV (high-definition television) and SDTV (standard-definition television) EDTV (Enhanced-Definition Television) EDTV stands for Enhanced Definition Television. The picture quality of EDTV is superior to that of standard analog TV (480i) but not as good as HDTV (1080i or 720p). EDTV displays the picture at a resolution of 852x480 (480p) lines in either 4:3 or 16:9 aspect ratios and it includes Dolby Digital sound system. EPG EPG stands for electronic program guide. It is a system displaying channels and program data on-screen. Flat-panel TV Flat-panel TV typically displays picture using gas plasma or LCD technology and is only a few inches thick. Frequency Response A technical specification describing the range and variation in amplitude of frequencies a speaker or other device is capable of accurately reproducing. The "+/- 3dB" notation represents the industry accepted margin of no more than 3dB variance above or below the theoretical ideal zero dB point. A change of 3 dB represents the smallest change in volume an average listener can perceive in a quiet room. Frequency response is measured in Hertz (Hz) - or cycles per second. High-pass Filter - A type of filter designed to pass the frequencies above (and reject those frequencies below) the filter's cutoff frequency (or crossover point). Front-projection TV Front-projection TV comprises 2 parts – a separate front projector (usually placed on a table or ceiling-mounted) and a reflective screen (or simply a wall). The projector is placed at one end of the room, the screen is at the other end, and the speakers may be placed wherever they will provide you good sound experience. The picture can be rather large but remember – the larger the picture, the more visible the pixels or scan lines and the darker the image. Ghosting Ghosting means multiple overlaid TV images or "ghosts" which you can notice around the objects while watching TV. Ghosting is caused by the broadcast signal traveling to your TV through various obstacles, for example hills or tall buildings, and your antenna picks up the original TV signal along with signals reflected by the obstacles. If the ghosting is changing rather than static, it may be caused by the signal reflected by flexible objects, for example trees. HDTV (High-Definition Television) HDTV stands for High Definition Television. This highest-resolution subset of Digital Television offers filmlike picture quality with impressive surround sound. With twice the vertical and horizontal picture resolution, the picture of HDTV is approximately twice as sharp as that of NTSC. HDTV has widescreen aspect ratio of 16:9 and Dolby Digital sound system. Currently used HDTV formats - 1080i and 720p both offer reduced motion artifacts like ghosting and dot crawl. Impedance (or impedance load) A term used to describe the total opposition to the flow of electrical current (music signals) in an AC circuit. Expressed in Ohms. Infrared Light (or IR) A portion of the light spectrum invisible to the naked eye and the most popular method of transmitting codes via line-of-sight from a hand-held remote control. Interlaced Scanning Interlaced scanning is a method based on the principle that the screen shows every odd line at one scan of the screen and then all the even lines in a second scan. There are 30 frames shown per one second and this can make larger screen flicker, which is the usual problem with interlacing. However, LCD and plasma screens cannot display interlaced signals and must first convert them to a progressive format and then they can display the transmitted images. IR Flashers These devices are connected to the flasher output terminals on the Main System Units. A flasher is a LED (light-emitting diode) which "flashes" infrared codes to your equipment in the same way your original remote controls do. IR Main System Units These devices act as input/output terminals for IR sensors, keypads, and IR flashers. Main System Units provide power and status feedback to the IR sensors and/or keypads connected to them. MSU's convert the data signals which are output from the sensors to pulses of voltage, which are then used to power IR flashers. IR Repeater System An infrared repeater system allows the user to receive, transmit, and output infrared commands to A/V components located in another room or behind closed doors. A basic system consists of four main components: IR Sensors, IR Cable, IR Main System Units, and IR Flashers. IR Router A device used to receive and route IR commands to specific source components or outputs independently. IR Sensors These devices receive the infrared codes from your hand-held remotes and convert them to data pulses. This data is transmitted via an IR Cable to a IR Main System Unit. Interference In terms of IR or RF (radio frequency) data transmission, interference represents any occurance or set of circumstances which may cause the system to operate intermittently or not at all. Interference that can effect IR repeater systems is generally either optical or electro-magnetic in nature. Optical Interference is categorized as interference caused by light, both visible and invisible. Sunlight contains vast amounts of infrared light, far more than the output of a hand-held remote control. Sensors are not able distinguish IR codes from rays of ambient sunlight, and may cause the sensor's flashback LED to flicker or stay constantly lit. Sources of optical interference may include bright reflections from windows, mirrors, swimming pools, shiny floors, or other objects which reflect light. Electro-Magnetic Interference (EMI) is generally caused by electro-magnetic fields or electrical noise corrupting the reception or transmission of data. EMI is commonly caused by televisions, light dimmers, variable speed control potentiometers, electronic ballasts found in fluorescent lighting, neon or halogen lighting, large appliances driven by motors, or AC line noise brought into the system by the power supply powering the IR MSU. LCD (Liquid Crystal Display) LCD stands for Liquid Crystal Displays. It refers to a flat panel technology which uses liquid crystals sandwiched between two glass plates for example in laptop computers, other small portable displays and also in televisions. Wide-screen HDTVs are available with displays of adequate resolution up to about 37 inches. Letterbox Letterboxing means copying the widescreen format with aspect ratio of 16:9 to video format with aspect ratio of 4:3. The result of this process is that the full picture is presented only on the middle part of the screen, with black bars above and below it. This arrangement is referred to as "Letterbox" and you can see it on your 4:3 TV while watching movies. On a 16:9 TV letterboxing does not block out so much of your screen and makes your experience more profound. Line-level Audio Signal Refers to an unamplified audio signal. Line-level audio signals are generally output from a source component (CD player, tape deck, TV, etc.) and are usually connected to an amplifier using RCA patch cables (interconnects).Low-pass Filter - A type of filter designed to pass the frequencies below (and reject those frequencies above) the filter's cutoff frequency (or crossover point). Multi-room Sound System A system able to play a single source in multiple rooms simultaneously. Multi-zone / Multi-source System A system able to play different sources in multiple rooms simultaneously. Normal IR Command An IR command which is issued as one short burst when a button on the remote control is tapped. For example; a "Play" command is a normal IR command (it only needs to be tapped) while a "Volume Up" command is a continuous IR command (it must be pressed and held). See "Continuous IR Command". NTSC (National Television Systems Committee) NTSC or National Television Systems Committee is the organization that develops technical standards for black-and-white television and color television. The term is also used to refer to the video-transmission standard used in the western hemisphere, Japan, and other Asian countries. NTSC established the 525-line (480 visible) analog broadcast TV standard. It is supposed to be soon replaced by digital broadcast standards.\ Ohm A unit of measure used to gauge both impedance (Z), and resistance (R). Over-the-air Broadcast (OTA) Over-the-air Broadcast is also called Terrestrial Broadcast. It is standard over-the-air broadcast to an antenna, as opposed to satellite or cable transmission. Parallel Circuit A parallel circuit consists of two or more current paths sharing a common output from an amplifier. This is the preferred method to be used when connecting multiple speaker pairs or volume controls. Note: Most amplifiers require impedance protection when making more than one parallel connection. If the impedance load being presented to the amplifier is lower than the manufacturer's recommended specification, the amplifier may not operate correctly and damage may occur. When connecting speakers or volume controls in parallel, the amplifier's outputs will be connected to their respective terminals on each speaker. For example, the amplifier's left channel positive output will be connected to the left channel positive connections on each pair of speakers (or volume control). Follow this same procedure for the remaining channels (left channel negative, right channel positive, and right channel negative). Picture-in-picture (PIP) Picture-in-picture is a television feature in which you can see one program inside a small window on the screen, while watching another program on the large background screen. You can choose whatever you wish – you can watch two TV programs simultaneously or you can watch TV and video or DVD at the same time. Pixel Pixel comes from the words "picture element" and it refers to the smallest element in a television picture. Pixels are single displayable video dots from which the overall picture is made up. Plasma Displays (PDP) Plasma display is created by thousands of tiny tubes filled by ionized gas in a plasma state. Ionized gas is very light and flat panel TVs made by this technique can be even hanged on the wall! Plasma displays offer excellent resolution and color and they are the most suitable for the home theatre. Pre-out (abbreviation for "preamplifier output") A set of connections on a preamp or receiver's rear panel which output a variable (relative to the setting of the volume knob) line-level audio signal. This signal is usually connected to an additional "slave amplifier" to power additional speakers or speaker pairs. Progressive Scanning Progressive scanning is used by some HDTVs. Progressive scanning offers rather smooth picture as 720 or 1080 horizontal lines are scanned progressively or in succession in a vertical frame that is repeated 30 times a second. Some displays, for example LCD and plasma use progressive scanning method, while CRTs may use progressive (e.g. in computer monitors) or interlaced scanning method. Rear Projection Rear projection is a TV system where the picture is projected against a mirror inside the cabinet and you can watch it as you would an average television. Until recently, the rear projection TVs comprised three CRTs but the new types of rear projection TVs include LCD. Receiver (or Stereo Receiver) An audio component featuring a built-in preamp, tuner, and amplification circuitry. Resolution Resolution reflects the density of lines, and dots per line which make up a visual image. It is measured by the number of pixels displayed. The level of resolution directly affects picture quality. Usually the higher number of lines and dots means also sharper and more detailed picture. Analog TV has a little over 200,000 color pixels while HDTV, with 1080 vertical pixels and 1920 horizontal ones, has more than 2 million pixels creating the image. RF (or Radio Frequency) A wireless method of transmitting information on any frequency within the electro-magnetic spectrum. SDTV (Standard-Definition Television) SDTV stands for Standard Definition Television. The SDTV picture, having either in 4:3 or 16:9 aspect ratios, is better and of higher quality than the one of NTSC, however, it does not reach the quality and resolution of HDTV. SDTV is based on 480 lines of vertical resolution and in both interlaced and progressively scanned formats. Set-top Box (STB) Set-top box is responsible for receiving, converting and sending the picture and sound of the broadcast to the associated television. If your HDTV-ready TV has no built-in HDTV tuner you must connect it to a compatible HDTV STB first. Until then it will not receive and display digital television programs. Sensitivity (or Efficiency) When referring to loudspeaker specifications, sensitivity generally specifies how loud a speaker will play with a single watt of power when measured from a distance of one meter. Series Circuit A series circuit is wired so that there is only one path for current to flow from the positive to the negative terminal. In a series circuit, each component is connected to the output of the first (+ -, + -, + -, etc.). This is the preferred method of connecting multiple IR flashers to a single flasher output terminal on a IR MSU. Speaker Selector A device capable of distributing the output of a single amplifier to those speaker pairs selected. Speaker selectors usually feature a "protection circuit" which protects the amplifier from driving the unusually low impedance load which results from the parallel connection of multiple speaker pairs. Tape-out (or Record-out) A set of connections on a receiver or preamp's rear panel used to feed the currently selected source to a cassette deck's record input for taping purposes. Watts per Channel This specification refers to an amplifier's maximum power output capability. For example, if amplifier's power is rated at 100 watts per channel into 8 ohms, it will only output 100 watts when turned all the way up. Widescreen Widescreen TV is the television with 16:9 aspect ratio. 16:9 is the aspect ratio of movie screen and widescreen DTV formats used in all HDTV (High Definition TV) and some SDTV (Standard Definition TV); it stands for 16 arbitrary units of width for every 9 arbitrary units of height. |
