AV/IT Glossary—27 Days of #AVabc—S



Signal—An electrical impulse or radio wave transmitted or received.


S/PDIF-Sony/Philips Digital Interconnect Format—A data protocol for compressed or uncompressed digital audio co-developed by Sony and Philips Electronics and now part of the larger AES/EBU audio standard. S/PDIF is often misconstrued as a connection type; however, S/PDIF audio can be found in products using either a 75 ohm coaxial connection or a TOSLINK fiber optic connection. S/PDIF is commonly found in Compact Disc and DVD players.

SACD-Super Audio Compact Disc—A very high fidelity, read-only optical disc format for both two-channel stereo and 5.0 (no sub-woofer) or 5.1 surround sound audio. SACD can store up to 10 times as much data as a standard audio CD, up to 7.95 GB. Support for SACD audio was added to the HDMI 1.2 specification in 2005.

Sag—A measure of the amount of sag in a fiber optic cable, taken at the midpoint of a span of cable between two points of support.

Sag Section—A section defining a span of fiber optic cable between two points of support.

Sag Span—A span selected within a sag section, used as a control to determine the proper sag, and therefore, tension of a fiber optic cable. At least two, and normally three sag spans in a sag section are required to sag a section properly.

Sag Tension—The tension at which a fiber optic cable is designed to be installed.

Sample Rate—The rate at which an analog signal is sampled. It is frequently expressed as kilosamples/sec (kS/s) or Megasamples/sec (MS/s. For example, 44.1 kHz is the standard sample rate for compact disks; 48 kHz is often used with digital audio tape (DAT) recording. A higher sample rate allows a higher frequency response. In order to accurately reconstruct a sound, the sample rate must be at least twice the highest frequency in the sound.

Sampling—The process of converting an analog audio signal into digital form by taking periodic “snapshots” of the audio signal at some regular interval. Each snapshot (sample) is assigned a number that represents the analog signal’s amplitude at the moment the sample was taken.

Sampling Frequency—The rate at which samples are taken when converting analog audio to digital audio. Expressed in samples per second, or, more commonly, in hertz; i.e., the CD format’s sampling frequency is 44.1kHz.

SAP-Second Audio Program—A feature of MTS television stereo audio, SAP permits the delivery of a second soundtrack for enhanced services such as second language or descriptive video services (DVS) for the vision impaired.

Saturation—Chroma, chroma gain. The intensity of the color, or the extent to which a given color in any image is free from white. The less white in a color, the truer the color or the greater its saturation. On a display device, the color control adjusts the saturation. Not to be confused with the brightness, saturation is the amount of pigment in a color, and not the intensity. Low saturation is like adding white to the color. For example, a low-saturated red looks pink.

Satellite Speaker—A small loudspeaker with limited bass output, designed to be used with a subwoofer.

Satellite Television—Entertainment or business video and audio transmitted via a satellite.

SAV—Start of Active Video. A term used in digital component video to indicate the onset of the active line.

Saw Filter—A hermetically sealed device, employing SAW (Surface Acoustic Wave) technology, which responds only to a very specific bandwidth. It permits a narrow frequency band to pass through while rejecting all other signals. A SAW filter has very steep shoulders cutting out everything that is outside its band of transmission. SAW filters have excellent out-of-band signal rejection quality eliminating, to a great extent, all unnecessary, spurious signals.

Saw Modulator—With the aid of SAW* technology special modulation used in TV transmission is easily achieved and a number of transmitting bands can be compressed into close broadcast ranges. An RF* modulator utilizing SAW* technology, produces a very clean and accurate signal on the screen.

SC-Subcarrier—The modulation sidebands of the color subcarrier containing the R-Y and B-Y information. A secondary signal containing additional information that is added to a main signal.

SC/H phase—Subcarrier to Horizontal phase. In NTSC video, this is the phase relationship of the subcarrier to the leading edge of horizontal sync. SC/H phase is correct when the zero crossing of subcarrier is aligned with the 50% point of the leading edge of sync. In PAL video, the SC/H phase is defined as the phase of the EU component of the color burst extrapolated to the half amplitude point of the leading edge of the synchronizing pulse of line 1 of field 1.

Scalability—The property of a system, a network, or a process, which indicates its ability to handle growing amounts of work in a graceful manner with a limit which is unlikely to be encountered.

Scaler—A device for converting video signals from one resolution or framerate to another: usually upscaling or upconverting a video signal from a low resolution (e.g. standard definition) to one of higher resolution (e.g. high definition television).

Scaling—A conversion of a video or computer graphic signal from a starting resolution to a new resolution. Scaling from one resolution to another is typically done to optimize the signal for input to an image processor, transmission path or to improve its quality when presented on a particular display.

Scan—(1) In video, to move an electron beam across the raster in a camera or monitor. (2) To feed visual information into a computer by means of an optical device called a scanner.

Scan Converter—Also called “video converter” or “TV converter,” a scan converter is a device that changes the scan rate of a source video signal to fit the needs of a display device. Examples: computer-video to NTSC (TV), or NTSC to computer-video.

Scan Doubler—A device used to change composite interlaced video to non-interlaced component video, thereby increasing brightness and picture quality. Also called “line doubler.”

Scan-Doubling—The process of making the scan lines less visible by doubling the number of lines and filling in the blank spaces. Also called “line-doubling.”

Scan Line—One sweep of a beam of electrons from left to right across a CRT display; also, one horizontal line of picture information in a video signal. In the NTSC system, each video frame is composed of 525 scanning lines (of which 480 are visible).

Scan Rate—The frequency of occurrence of a display drawing one line of information.

Scart—A European video-audio connector widely used in consumer equipment. The SCART connector has 21 pins, carrying two audio channels - in and out, video channels - in and out, RGB signals, ground and some additional control pins. In order to connect two VCRs or a VCR to a monitor only one SCART-to-SCART cable is needed, avoiding the cable jungle of video and audio inputs and outputs, which may confuse the home user. Simplicity of connections is the main advantage of the SCART system, however, it is not recommended for professional use as the physical connection is quite weak and signal leakage is too high.

Scattering—A source of optical signal loss in a fiber optic system, caused by the scattering of light due to small particles and other imperfections in the fiber.

Screen—The front of a direct-view television’s CRT picture tube, the front of a rear-projection TV onto which an image is projected, or a separate material onto which a front projector projects a video image.

Screen Gain—Describes the distribution of light reflected off a projection screen. The amount of gain is compared to a matte-white screen, which reradiates light and distributes it with perfect uniformity.

Screen Splitter—An electronic process, which allows the video screen to be split horizontally or vertically showing the signal before processing on one part of the screen and the processed signal on the other. Full screen splitting provides precise fingertip control of the video enhancement process. Screen splitting is a proprietary process developed by Kramer Electronics. It has been adapted at the consumer level in video processing equipment and is now used worldwide.

Scribe—Scratching the surface of the fiber so that it can be precisely and cleanly cut at a right angle to the fiber axis.

Scribe Tool—A device consisting of a scribing blade, usually made from diamond or tungsten carbide, used to scribe, or score a fiber to allow for a clean break and a smooth endface.

Scrolling—The displayed image (or interfering noise on the image) rolling constantly on the screen.

SCSI—Small Computer System Interface. Pronounced “skuzzy.” An industry-standard input/output bus for peripheral computer devices, such as hard disks and CD-ROM drives. A standard peripheral bus on Mac computers. Improvements, such as the number of data lines and speed, have been made to the original SCSI to become SCSI-2 and SCSI-3.

SDI—Serial Digital Interface. Standard definition video is carried on this 270 Mbps data transfer rate. Video pixels are characterized with a 10-bit depth and 4:2:2 color quantization. Ancillary data is included on this interface and typically includes audio or other metadata. Up to sixteen audio channels can be transmitted. Audio is organised into blocks of 4 stereo pairs.

SDI Check Signal—One of the digital test signals used for testing SDI PLL (Phase Locked Loop) and equalizer circuitry.

SDSL—Symmetrical Digital Subscriber Line. Offers bandwidth of up to 2.3Mbps upstream and downstream over a single twisted pair copper phone line, over distances up to about 10,000 feet on an unrepeatered basis.

SDTV—Standard digital television. A serial digital format whose samples and timing are derived from 4:2:2 digital component video sources. The main difference between existing digital component video and SDTV is an MPEG-2 compression step to reduce the channel bandwidth.

Seamless Switching—A feature found on many Extron video switchers. This feature causes the switcher to wait until the vertical interval to switch. This avoids a glitch (temporary scrambling) which normally is seen when switching between sources.

SECAM—Sequential Couleur Avec Mémoire, or “sequential color with memory.” A composite color transmission system that potentially eliminates a need for both a color and hue control on the monitor. One of the color difference signals is transmitted on one line and the second is transmitted on the second line. Memory is required to obtain both color difference signals for color decoding. This system is used in France, North Africa, Russia, Saudi Arabia, and many Eastern European countries. It is similar to PAL but produces color signals in a different manner. SECAM uses 625 horizontal scan lines, 50 fields per second (625/50).

SED—Surface-conduction Electron-emitter Display. SED is a new type of flat-panel display technology developed by Canon and Toshiba. SED is capable of high levels of brightness and color performance, as well as a wide angle of visibility, that on a par with a CRT. Large screens can be produced by simply increasing the number of electron emitters in accordance with the required number of pixels.

Selectivity—Tuner specification describing the tuner’s ability to reject unwanted stations. Good selectivity is important to those who live in cities, where stations are closely spaced on the broadcast spectrum.

Sensitivity—A standard way to rate audio devices like microphones, loudspeakers, and amplifiers. For loudspeakers, sensitivity is rated by applying 1 watt of power to the speaker and measuring sound pressure level (SPL) at one meter. For microphones, sensitivity is expressed as the minimum input signal required to produce a standard output level. For a power amplifier, sensitivity is rated as the input level required to produce 1 watt of power output into a specified load impedance, typically 4 ohms or 8 ohms.

Sepia—A process used in photography to generate a brownish tone in pictures providing an antique appearance. The same idea has been electronically adapted in video special effects* generation. A color picture can be converted to sepia tones or a black and white picture can be colored in sepia.

Serial Communication—Serial communication is a communication technique used in telecommunications wherein data transfer occurs by transmitting data one bit at a time in a sequential order over a computer bus or a communication channel. It is the simplest form of communication between a sender and a receiver. Because of the synchronization difficulties involved in parallel communication, along with cable cost, serial communication is considered best for long-distance communication.

Serial Data—A way to transfer information by breaking the characters of a word into bits, which are then transmitted sequentially along a single line. Compare to parallel, which uses more than one line.

Serial Port—An input/output connection on the computer that allows it to communicate with other devices in a serial fashion data bits flowing on a single pair of wires. The serial port is used with RS-232 protocol.

Serial to Parallel Converter—A Deserializer which converts between Serial Digital Video and parallel Digital Video, and is mainly used for interfacing the two digital formats.

Serration Pulse—A vertical synchronizing pulse divided into a number of small pulses, each acting for the duration of half a line in a television system. Serration pulses are used to keep the horizontal oscillator synchronized during the vertical sync pulse interval.

Service Loop—A deliberately allotted slack of fiber optic cable, in a splice tray, closure, vault, or communications output, to accommodate future needs.

Servo—A very accurate electromechanical or motor control system found in video and audio tape recorders.

Set-Top Box (STB)—A device that receives and decodes digital television signals. A set-top box can also include a satellite receiver and/or a hard-disk-based digital video recorder (DVR).

SFP—Small form-factor pluggable. The SFP is an interface used in fiber optic connections for direct signal connections or packet switched networks.

Shadow Mask—A metal plate with holes or vertical lines that is used to determine exactly where the electron beam strikes the CRT screen.

Sharpness—The definition of the edges of an image.

Sharpness Control—Same as Peaking control.

Sheath—Also known as a cable jacket, the outer protective covering of wire or fiber optic cable.

Shield—1. a physical layer in some cables used to protect signals and sometimes used as a return path for current. Three basic types of cable shielding: foil, braid and combination.

Shielded Loudspeaker—A loudspeaker lined with metal to contain magnetic energy inside the speaker. Shielded loudspeakers are used in home theater because the speaker’s magnetic energy can distort a video monitor’s picture.

ShiftLock™—An Extron feature used to lock video displays together when using Extron VideoShift™, synchronizing the movement of their images.

Short Circuit—The electrical connection between any two conductors of the electrical system from line-to-line or from line-to-neutral (Basic Electrical Theory, by Mike Holt). (A short circuit is not the same as a ground fault.)

Shotgun Microphone—A long, cylindrical, highly sensitive, unidirectional microphone used to pick up sound from a great distance.

Shuttle—A provision available on some VCRs for fast search of frames while playing a video tape.

Sibilance—S, sh, and ch sounds in spoken word or singing

Signal Generator—Test equipment instrument that produces calibrated electronic signals intended for the testing or alignment of electronic circuits or systems.

Signal Loss—A video problem that shows up as a faint picture for lack of video information.

Signal Noise—A random fluctuation in an electrical signal, a characteristic of all electronic circuits.

Signal to Noise Ratio—Also stated as "S/N ratio". The ratio is expressed in decibels as a ratio between the audio or video signal level and that of the noise accompanying the signal. The higher the S/N ratio, the better the quality of the sound or picture.

Sine X/X—A video test signal for testing frequency response.

Single-Link DVI—The electrical signaling used to transmit data over DVI is known as transition minimized differential signaling, or TMDS. A single TMDS link carries three data channels and one clock signal, with a maximum video frequency of 165MHz, capable of standard resolutions up to 1920x 1200 pixels. See also “Dual-Link DVI.”

Single Pass Transform—Transformation process which is carried out making only one examination of a data set. A single pass transform is required to maintain a low delay.

Single-Phase Power—Alternating current electrical power supplied by two current carrying conductors. This type of power is used for residential and some light-commercial applications.

Singlemode Fiber–SMF—An optical fiber with a small core, through which only a single mode can propagate.

SIS™-Simple Instruction Set™—A set of commands developed by Extron that allows easy RS-232 control of certain Extron products with a minimal number of characters in the commands and responses.

Skew—Refers to the timing difference which occurs when electrical signals which are traveling over different pairs of cables reach their destinations at different times. The different arrival times of the signals may present a problem when simultaneous arrival with no delay is required.

Skew-Free—A reference to special twisted pair cable in which the length differences between cables reduced to a minimum, thus reducing cable skew.

SL—The Extron product designation for ShiftLock.

SLA—Service Level Agreement. An agreement between a network service provider and the user, defining an established a set of metrics to measure the service delivered relative to the service delivered. A SLA typically identifies the bandwidth delivered, Quality of Service and service response time.

Slew Rate—The ability of audio equipment to reproduce fast changes in amplitude. Measured in volts per microsecond, this specification is most commonly associated with amplifiers, but applies to most types of audio products. In amplifiers, a low slew rate “softens” the attack of a signal, “smearing” the transients and sounding “mushy.” Since high frequencies change in amplitude the fastest, this is where slew rate is most critical. An amp with a higher slew rate will sound “tighter” and more dynamic.

SMATV—Satellite and Master Antenna Television system; a television system where satellite and broadcast programs are received via a master antenna array and distributed to users over coaxial cable or fiber optic cable.

Smearing—A video problem where objects such as horizontal bars extend past their boundaries. Also called “over-peaking.”

SMPTE—Society of Motion Picture and Television Engineers. A global organization, based in the United States, that sets standards for baseband visual communications. This includes film as well as video and television standards.

SMPTE 125M—A standard which defines the interface for system M (525/60) digital television and which is based on CCIR 601*. This standard is defined for use in television studios for up to 300m distance. It is a Bit-Parallel digital interface for component video signals at 4:2:2* digitization format.

SMPTE 244M—A standard which defines the interface for system M/NTSC (525/60) digital television and which is based on CCIR 601*. This standard is defined for use in television studios for up to 300m distance. It is a Bit-Parallel digital interface for composite video signals at 4xFsc sampling frequency. This standard defines the sampling parameters, the relationship between sampling phase and color subcarrier and the digital levels of the video signal.

SMPTE 259M—Defines the SDI serial digital interface common to most standard definition digital video products. SMPTE 259M includes several data rates, including 143 Mbps (NTSC composite digital), 177 Mbps (PAL composite digital), 270 Mpbs (4:2:2 component digital, 4:3 standard video aspect), and 360 Mbps (4:2:2 component digital, 16:9 widescreen video aspect). Of the group, 270 Mbps and 360 Mbps are the most common data rates.

SMPTE 292M—Defines the HD-SDI high definition serial digital interface. SMPTE 292M has data rate of 1.485 Gbps for 4:2:2 component digital in 16:9 widescreen video aspect. Full bandwidth HD-SDI can be transmitted 300 feet (100 m) on standard RG6 coaxial cable, and more than 60 miles (100 km) using fiber optic technology. SMTPTE 292M is considered a single link HD-SDI signal, in that only one coaxial cable is required to transmit the data.

SMPTE 310—A broadcast standard for transmitting one or more DTV – digital television channels, and ancillary content, as part of a single data stream.

SMPTE 372M—Defines a full bandwidth, 4:4:4 RGB color space and bandwidth up to 2.97 Gbps, which is sufficient for 1080/60p and 1080/24Psf video streams. SMPTE 372M is most commonly associated with dual-link HD-SDI, wherein two coaxial cables are used to carry alternate pixels, thus doubling the data rate and available resolution. The “Super2k” format in digital cinema, 2048x1080, progressive scan, 4:4:4 RGB color space, is the highest data rate possible with one dual-link HD-SDI connection.

SMPTE 424M—Defines a full bandwidth, 4:4:4 RGB color space and bandwidth up to 2.97 Gbps on a single coaxial cable. SMPTE 424M is colloquially known as 3G-SDI, a term used to describe 2.970 Gigabits per second digital video over a single-link coaxial cable. 3G-SDI is capable of supporting HDTV 1080p video at 50 or 60 frames per second. Most 3G-SDI terminal equipment, such as Extron 3G-SDI matrix switchers, simple switchers, distribution amplifiers, cable equalizers, and fiber optic extenders, is capable of supporting standard SDI data rates from 270 Mbps to 2.970 Gbps.

SMPTE Pattern—The video test pattern consisting of color, black, and white bands used as a standard for setting up video equipment.

SMPTE/DCI P3—A color space defined within the Digital Cinema Initiatives - DCI specification for digital cinema systems. SMPTE/DCI P3 offers a color gamut wider than the ITU-R Recommendation BT.709 or sRGB color spaces, but less than ITU-R Recommendation BT.2020.

SMTP—Simple Mail Transfer Protocol. Internet standard for e-mail exchange across systems/networks on the Internet.

SNMP—Simple Network Management Protocol. Allows for management of network devices with administration software.

Snow—Visual noise in a video picture giving the appearance of white flecks of snow.

Software—The programs used to instruct a processor and its peripheral equipment to perform prescribed operations.

Software Decoder—A software decoder provides a means to decode audio/video streams in software without requiring use of a dedicated hardware appliance. Software decoders are typically used on a PCs using a browser page, media player or special purpose application.

SOG—Sync On Green. The combined horizontal and vertical sync signals are integrated with the green video signal.

SONET—Synchronous Optical Networking. A standardized multiplexing protocol that transfers multiple digital bit streams over optical fiber using lasers or light-emitting diodes (LEDs).

Soundfield—A region in a material medium in which sound waves are being propagated. Sound fields depend not only on the sound power and directional characteristics of the sound source, but also on the properties of any medium it passes through is reflected, absorbed or diffused by. Expressed in decibels (dB SPL).

Sound Level Meter—An instrument designed to measure sound pressure level.

Sound Masking Systems—Sound masking systems add artificial or natural sound to an environment such as an office to mask unwanted sound & foster speech privacy among coworkers in a workspace.

Sound on Sync—A method of inserting a sound channel into an analog video signal. The sound channel is modulated and inserted into the line sync signal. A special device is needed in order to retrieve the audio information. It is a good way to add a sound channel to a video signal (adding a second channel for stereo, for example).

Soundstage—The impression of soundspace existing in three dimensions in front of and/or around the listener.

Source—The optical source in a fiber optic system, usually an LED or laser diode.

Source Components—A/V components that provide audio and video signals to the rest of a home-theater system. Digital video recorders, DBS dishes and receivers, and DVD players are source components.

Source Switching—Function performed by an A/V receiver or A/V controller that selects which source component’s signals are fed to the speakers and video monitor.

Spade Lug—A speaker termination with a flat area that fits around a binding post.

Spanning Tree—IEEE 802.1d. is a protocol that allows networks to prevent loops, or multiple paths from developing between a source and a destination. Network routers communicate with each other using spanning tree protocol to prevent traffic from reaching unnecessary destinations. Spanning tree and other routing protocols prevent multicast video traffic from flooding networks with unnecessary, disruptive traffic.

Spatial Resolution—A measurement of the resolution in a single frame of video. The horizontal resolution multiplied by the vertical resolution.

S/PDIF (Sony/Philips Digital Interface Format)—Standardized method of transmitting digital audio from one component to another.

Speaker (conical) Coverage—Ceiling speakers, much like a spot light, generally project audio in a conical coverage pattern. As with any device featuring a conical coverage pattern, the higher it’s mounted, the larger the circle of coverage. As the area of coverage increases, audio amplification wattage must also increase to maintain the same sound pressure level per unit of area of coverage.

Speaker Polarity—Loudspeakers of all types have a positive and a negative polarity. A speaker cone that moves forward (out) when a positive voltage is applied is said to have “positive polarity”; conversely, a speaker cone that moves backward (in) when a negative voltage is applied is said to have “negative polarity.” Speakers must be wired in such a way to ensure that they are “in phase”, that is, all speaker cones are moving in the same direction, in or out, at the same time. Audio test generators, such as the Extron VTG 300 and VTG 400, include a test tone (typically a “click” or “pop”) that’s used to check speaker polarity.

Speakon™—specialized connector used to hook up loudspeakers without causing a short circuit; allows connection of loudspeaker while working, or hot.

Special Effects—Artistic effects added to a video production in order to enhance the viewing of a tape. Special effects may vary from the limited addition of patterns, the mixing of several video images together, completely changing color and texture of the image, to sophisticated digital effects such as shrinking the picture, page flipping, three-dimensional effects, etc. Special effects generators are usually used to create special effects*.

Special Effects Generator—Devices designed to generate special effects*. The simplest devices can process a single video signal - changing its color, generating sepia* tones, inverting the picture to a negative form, posterizing* the image and fading* or breaking up the image into various patterns. More sophisticated equipment utilizes several video sources, computer-generated graphics and sophisticated animation* with digital effects. Many special effects generators have a built-in color generator for adding color or border lines to the video image.

Spectrum Analyzer—An device used to measure and analyze the frequency spectrum of an input signal, usually amplitude (vertical) vs. frequency (horizontal).

Speed of Light—2.998 x 10e8 meters per second.

Spherical Aberration—Light passing through the edges of the lenses can also have focal lengths different from those passing through the center is called spherical aberration.

SPEG—Sync Pulse Generator, sometimes called Black Burst Generator. A device, which generates sync, burst, subcarrier and other signals and is used as a reference source for video and television studios. Some SPGs generate Color Bars* as well, that may be recorded as reference signals at the beginning of a video tape or used for equipment alignment.

SPL Meter—A device for measuring the sound pressure level created by an audio source.

Splice—A permanent connection between the ends of two optical fibers by mechanically joining them together, or heating to fuse them together.

Splice Closure—A housing designed to protect splices in a optical fiber from damage, sealing them from the external environment.

Splice Organizer—A device that facilitates the splicing of optical fibers, as well as their permanent storage.

Splice Panel—A rack or wall-mounted panel that allows fiber optic cables to be organized and spliced. The panel holds splice trays, cable routing, and slack storage.

Splice Protector—In fiber optics, a device used to provide protection and mechanical strength to a fusion splice, so that it can be handled and organized into a splice tray or other storage.

Splice Tray—A container that is used to secure, organize, and protect individual spliced optical fibers.

Split Screen—A video effect where portions of images from two sources divide the screen.

Spring Clips—Cheap speaker terminations found in budget A/V receivers.

sRGB—A color space widely used in computers, monitors, and the Internet, as well as consumer digital cameras, printers, and scanners. sRGB incorporates the same color space primaries as defined in ITU-R Recommendation BT.709, the international standard for high-definition video.

Staircase—A video test signal which generates several signal stairs at different levels (amplitudes) for measuring and evaluating non-linearity.

Stapler Cleaver—A fiber optic cleaver that is shaped similar to a stapler.

Star—A network topology where all network devices are connected to a central network device that is usually a hub or a switch.

Static IP—An IP address that has been specifically (instead of dynamically see “DHCP”) assigned to a device or system in a network configuration. This type of address requires manual configuration of the actual network device or system and can only be changed manually or by enabling DHCP. Also see "DHCP."

Static Mesh—A basic de-interlacing process used in scalers for video content that contains no movement. This type of processing results in a sharp image with crisp details but will cause images to tear when motion occurs.

Step Index Fiber—A fiber in which the refractive index is uniform throughout the core. On the other hand, for a graded index fiber, the refractive index of the core varies radially between the fiber axis and the cladding.

Stereo—A process of using separate audio signals on separate channels for the left and right audio, thereby giving depth, or dimension to the sound.

Stereo Mixing—Simultaneous mixing and processing of both left and right audio signals.

Stereophonic—Commonly shortened to "stereo", input from all microphones is split into at least two channels before driving the signal through the loudspeakers.

Stereo Simulation—An electronic process by which a mono audio signal is broken down into two signals, creating a three-dimensional stereophonic effect from a monophonic signal. In many instances, especially in old recordings, it is impossible to re-record the original signal in stereo. In such cases, high quality stereo stimulating circuitry can generate a three-dimensional effect covering the whole audio spectrum in both channels. True stereo simulation is achieved by manipulating the monophonic audio signal on the basis of frequencies and phases, taking into consideration the physical aspects of hearing (distance between the human ears, human frequency hearing response and the psychological perception of sound).

Stillstore—An electronic device for digital capture and playback of TV and video pictures, using a storage device such as a Hard Disk* or RAM (Random Access Memory).

Straight Tip–ST—A popular legacy fiber optic connector with a twist lock design similar to a BNC. The ST connector has a 2.5 mm ferrule.

Streaming—A method of transmitting or receiving data (especially video and audio material) over a computer network as a steady, continuous flow, allowing playback to proceed while subsequent data is being received.

Streaming Video and Audio—Sequence of "moving images" or "sounds" sent in a continuous, compressed stream over the Internet and displayed by the viewer as they arrive. With streaming video or audio, a web user does not have to wait to download a large file before seeing the video or hearing the sound.

Stripper—A tool used to remove the jacket that surrounds a cable or an individual wire within the cable. In fiber optics, a stripper is used to remove the buffer coating from an optical fiber.

Sub-Frame Compression—Compression which is not carried out on an entire frame of video, but only a part of a video frame.

Subnet Mask—Number of bits of the network address used to separate the network information from the host information in a Class A, Class B, or Class C IP address, allowing the creation of subnetworks. In binary notation, a series of 1s followed by a series of contiguous 0s. The 1s represent the network number; the 0s represent the host number. Use of masks can divide networks into subnetworks by extending the network portion of the address into the host portion. Subnetting increases the number of subnetworks and reduces the number of hosts.

Subscriber Connector–SC—A popular fiber optic connector that features a snap (push-pull) coupling type. Being replaced by the LC in most applications.

Subtractive Color Process—Process used in color printing. Mixing cyan, magenta, yellow, and black (CMYK) produces millions of desired colors. Examples: 0% of C, M, Y and K = white (no ink); 100% of C and M = red; 100% C, M, and Y = process black. Also see "Additive color process."

Subwoofer—A loudspeaker designed to reproduce only the very low end of the audio frequency range, typically one or two octaves between 20 Hz and 80 to 100 Hz.

Summing Amplifier—A device which combines the left and right channel audio signals into a single mono channel. It is useful in multi-speaker mono paging systems, or in large stadium and church environments.

Super Audio CD (SACD) Disc—Format that can deliver high-resolution multichannel or 2-channel digital audio.

Super Cardioid Polar Pattern—The exaggerated heart-shape of the area that a highly directional microphone is most sensitive to sound.

Super Physical Contact–SPC—In fiber optics, a specific endface polish for a connector to achieve typically a -50 dB return loss in singlemode applications. SPC polished connectors can be used with PC or UPC polished connectors but are not compatible with APC polished connectors. Intermixing APC polished connectors with UPC/SPC/PC polished connectors can damage the fiber optic cable or equipment. Multimode applications always use PC, SPC, or UPC polished connectors.

Superimposition—Placing one image over another so that both may be seen at the same time. The effect can be achieved in many ways: by more than one exposure on a single piece of film, by multiple printing, or by registered projection. Abbreviated “super.”

Super-vga—A computer graphics format beyond [[VGA]] Super [[VGA]] displays 16 colors at resolutions of 800x600 and 1024x768 pixels, as well as 256 colors at 640x480 and 800x600 pixels resolution. The 640x480 at 256 colors is the most suitable for video use (after conversion to video) with almost natural colors.

Surface-Conduction Electronemitter Display (SED)—Display technology developed by Canon and Toshiba that delivers a CRT-quality picture in a flat-panel form-factor.

Surface Mount Microphone—Also called a boundary microphone, placed on a table to pick up sound. Used in boardrooms and other environments where a number of talkers must be "picked up" and where the microphone needs to remain unobtrusive.

Surround Decoder—A circuit or component that converts a surroundencoded audio signal into multiple audio signals that can then be amplified. A Dolby Digital decoder takes in an encoded Dolby Digital signal and outputs a 5.1-channel (left, center, right, left surround, right surround, subwoofer) audio signal.

Surround Decorrelation—A THX technology that makes the sound in the monophonic left and right surround channels in a Dolby Surround signal slightly different.

Surround Delay—A technique of delaying the signal to the surround channels to increase the apparent separation between the front and surround channels.

Surround Mode—A setting on A/V receivers and A/V controllers that determines what surround decoding or signal processing is performed on the audio signal.

Surround Sound—An audio recording and playback format that uses more than two channels, and is reproduced with two or more loudspeakers located behind the listener in addition to the loudspeakers in front.

Surround Speakers—Speakers located beside or behind the listener that reproduce the surround channels of surround-sound¬–encoded audio programs.

SVGA—Super VGA. A screen resolution of 800x600 pixels and above.

S-VHS—Super-Video Home System. A high band video recording process for VHS that increases the picture quality and resolution capability. Also see "S-video."

S-video—A composite video signal separated into the luma (“Y” is for luma, or black and white information; brightness) and the chroma (“C” is an abbreviation for chroma, or color information).

Sweep—In audio, a sequence of puretone frequencies used to generate a frequency response curve.

Switch—A device that cross-connects network devices. Today, switches are broadly deployed on modern industrial and consumer networks. Switching is a layer 2 function. Ethernet frames are delivered between MAC address connected to network switches.

Switched Fabric—A network topology where network nodes connect with each other via one or more network switches (particularly via crossbar switches, hence the name). The term is in contrast to a broadcast medium, such as early forms of Ethernet.

Switcher—(1) A device that allows a selection between more than one source, such as video cameras, VCRs, etc. In audio/video, switchers are a means of connecting an input source to an output device or a system. Also see “Matrix switcher.” (2) A term often used to describe a special effects generator; a unit that allows the operator to switch between video camera signals. Switchers are often used in industrial or security applications to switch between video cameras that view certain areas for display on a monitor, or system of display devices. These kinds of switchers do not have sync generators. Also see "Matrix switcher."

SXGA—Super Extended Graphics Array. A graphics standard with a resolution of 1280x1024 (1,310,720 pixels), with an aspect ratio of 5:4. This exceeds XGA (1024 x 768, at 786,432 pixels).

SXGA+—Introduced in 2004, a graphics standard with a resolution of 1400x1050 (1,470,000 pixels) with an aspect ratio of 4:3.

SxRD Silicon xTal Reflective Display—A reflective liquid crystal display technology from Sony that’s capable of very high resolutions and a very high contrast ratio. SxRD equipped projectors are capable of resolutions up to 4096 x 2160 pixels, or four times the resolution of HDTV (1920x1080).

Symmetrical Processing—Two processes are symmetric if the input process is of equal magnitude and complexity to the output process. The encoding and decoding processes in the PURE3 codec are symmetric.

Sync-Synchronization—In video, sync is a means of controlling the timing of an event with respect to other events. This is accomplished with timing pulses to insure that each step in a process occurs at the correct time. For example, horizontal sync determines exactly when to begin each horizontal scan line. Vertical sync determines when the image is to be refreshed to start a new field or frame. There are many other types of sync in a video system. (Also known as “sync signal” or “sync pulse.”)

Sync Generator—A circuit that produces sync impulses used to control the time when certain events happen electronically. Also known as a “synchronizing pulse generator.”

Sync Polarity—(1) A circuit can be designed to operate on the positive-going or negative-going part of the sync pulse. Some equipment has a sync polarity option switch to allow selecting which edge (plus or minus) to trigger on. (2) This refers to the duty cycle of the sync signal. A positive polarity sync signal is low most of the time, and high for a short time. Negative polarity sync is high most of the time and low for a short time.

Synchronisation—Timekeeping which requires the coordination of events to operate a system in unison. Synchronisation in video systems can refer to a number of items. Lip-sync is the synchronisation of audio and video. Genlock refers to alignment of vertical sync in video signals. Framesync or framelock refers to the alignment of video frames in systems with multiple video sources.

Sync Restoration—A process which replaces distorted and missing sync* information with good synchronization pulses generated by the restoring device. In many instances, during video editing* or multiple generation copying, sync pulses are lost or distorted. Sync restorers check the incoming syncs, analyze the frequencies involved and generate new, fully restored syncs, which replace the faulty source syncs.

Sync Stripping—Sync stripping is an electronic process, done either with discrete components or with special electronic chips, whereby the sync information is separated from the rest of the video information for timing correction, clamping and other purposes.

Synthetic Images—Synthetic images are produced in artificial processes, for example in video processing or computing systems.

System—A compilation of multiple individual AV components and sub-systems interconnected to achieve a communication goal.

System Matching—The art of combining components to create the most musical system for a given budget.

System Switcher—An A/V switching device that also communicates with other components in a system including room lights and motorized devices. For instance, in addition to controlling a projector, a system switcher can turn lights on and off and raise and lower a motorized projector screen.

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