S S-100 bus Group of 100 parallel common communication lines, each of which is able to carry one bit or signal through the entire computer. S/M Sort/Merge. S/MIME Secure multipurpose Internet mail extension, an e-mail security specification. S/MIME encrypts and authenticates e-mail messages for transmission over simple mail transfer protocol (SMTP) networks. SAA See Systems Applications Architecture. safe title area The central portion of a video frame where text and graphics can be placed that will not extend beyond the visible portion of the screen when viewed on some TVs or monitors. SAM 1. Sequential Access Method (IBM) {NS}. 2. Scientific Accelerator Module. sampling Process by which generalizations for an item (a system file transfers, traffic volume) are drawn on the basis of representative and random checking and controlling of samples. SAPI See service access point identifier. SAR Storage and retrieval device. A tape changer that holds up to 300 rolls of microfilm. satellite communications The use of a satellite with a self contained energy source to transmit radio communication signals back to earth. satellite office (exchange) A local office (or exchange) on the low level of a telephone network hierarchy, that is associated with another local office and has no route switching functions except those toward the associated higher level local office. saturated recording An optical recording device which causes the medium to stop absorbing light when the mark is fully formed. saturation In graphics, refers to the amount of a color. saturation testing Program testing with a large volume of messages intended to expose errors that occur infrequently and can be triggered by such rare coincidences as two different messages arriving at the same time. Also called volume testing. saved-number redial A feature that allows a station to automatically redial a previously dialed and saved number. SAW Surface Acoustic Wave. The newest type of touchscreen. It senses molecular waves traveling over a clear glass overlay. SCA See short code address. scale to gray Improving document images by adding gray pixels to fill in jagged edges of characters which have been magnified to a larger size. scaled point size A font's point size that approximates a specified point size for use on the screen. scaling Process of uniformly changing the size of characters or graphics. scan To convert human-readable images into bit-mapped digital machine-readable code. scan head The part of the mechanism of a scanner that optically senses the text or graphic as it moves across a page. scan line The pixels that result from one sweep of a linear-type scanner, such as that in a fax machine. scan rate Number, measured in times per second, a scanner samples an image. scanner A device that optically senses a human-readable image and contains software to convert the image to machine-readable code. scattering Loss of signal that occurs in fiber optical transmission when lightwaves strike molecules and imperfections in the core of the fiber. SCC (specialized common carrier) See other common carriers. schematic Diagram that specifies the electrical components of a circuit or system. SCOOP Self COupled Optical Pickup. An optical drive design that combines the functions of the laser reading device with the photodetector used to accept tracking and focus error signals. SCOPE Operating system (Control Data). SCP 1. Supervisory Control Program (Unisys){NS}. 2. System Control Processor{NS}. 3. System Control Program{NS}. 4. Systems Control Programming (IBM). SCPC See single channel per carrier. scrambler Device that deliberately distorts transmitted signals to make them unintelligible at the receiving end unequipped with a descrambling device. screen The display area of a video terminal or monitor. screen angles Angles at which halftone screens are placed over an image to avoid moire patterns or to make up for poor reproduction. Common angles in four color process are: black = 45 degrees; magenta = 75 degrees; yellow = 90 degrees; cyan = 105 degrees. screen capture Transferring the current on-screen image to a text or graphics file. screen dump Printing the current on-screen image. In a DOS machine, the command is Shift-PrtSc. screening The process of wrapping electrical conductors with metallic foil or braid to insulate the conductors from interference. Also called shielding. screening Converting a continuous tone photograph of artwork into a halftone. scroll To move up or down through text or graphics in order to see parts of the file or image that cannot fit on the screen. Moving left or right is actually called panning. scroll arrow On-screen arrow that is clicked in order to scroll the screen in the corresponding direction. SCSA See signal computing system architecture. SCSI (Small Computer Systems Interface) An interface standard for PCs that connects up to seven peripheral devices. SCU 1. Storage Control Unit{NS}. 2. System Control Unit{NS}. 3. Station Control Unit{NS}. 4. System/Memory Control Unit. SDA See source data automation. SDAID System Debugging Aids (IBM). SDDI Shielded distributed data interface. SDI Standard Disk Interconnect (Digital Equipment). SDL Software Development Language (Unisys). SDLC See Synchronous Data Link Control. SDM See space-division multiplexing. SDMA Shared Direct Memory Access. SDU Station Display Unit. SECAM Sequential and memory color television. Television system used in France and most Eastern European and Middle Eastern countries. secondary channel Transmission channel having a lower rate than a primary channel in a system where two channels share the same interface. secondary station A station on a network that has been selected to receive a transmission from the primary station. The assignment of secondary status is controlled by the primary station and normally remains in force for the duration of the transmission. secondary storage Another name for off-line. Refers to tape backups and transaction log recorders. Also used to create distribution copies. secretarial intercept PBX feature enabling a secretary's phone to accept an executive's calls even if the executive is called directly. sectional center Class 2 switching center. See also class of exchange. sector The smallest addressable unit of a disk's track. seek error The inability of a drive to find the user's request, usually because of a disk flaw or vibration. selection Addressing a terminal and/or a component on a selective calling circuit. selective calling The ability of the transmitting station to specify which of several stations on the same line is to receive a message. selective ringing Ringing only the requested party on a party line. self diagnostics A PBX with this feature can monitor itself for system failures and ensure fault-free processing. self-learning Some bridges are self-learning; that is, the bridge determines the location of devices by examining the source address of received packets to develop routing tables." self-relocating program Program able to be loaded into any main storage area, and that has the capacity to alter its address so that it can be executed at the new location. self-routing See Spanning Tree Algorithm. sender Equipment that sends out the routing digits and the called number. sensitive layer The layer in an optical medium where the data is recorded; it may be composed of more than one layer or materials. It is sandwiched by protective and supporting layers. sensitivity The measure of the light dose needed to mark an optical medium. separations Color separations. The result of filtering a color imaging into its primary color elements. Sequenced Packet EXchange protocol (SPX) Novell's XNS implementation that provides the guaranteed delivery services IPX does not. sequencing Dividing a data message into discrete units for transmission where each unit has its sequentially numbered place in the whole to facilitate reassembly. sequential Events that occur in a particular time or code order. sequential access Process of gaining entry to data by sequential method before arriving at the required information. Contrast with random access. sequential data set Data that is assembled on the basis of its successive physical position. serial Reference to the processing of successive items through a single facility. serial access Referring to the consecutive transmission of data to or from storage. serial call Feature that enables the attendant to program a call to return to the attendant position after the extension to which it was connected hangs up; the caller can then be connected to another extension without redialing. serial interface Mechanism that converts a parallel data arrangement to a serial form to be used for data transmission. Serial Line Interface Protocol (SLIP) A protocol that allows data to be exchanged between computers. serial port A socket on a computer used to connect a modem, mouse, scanner, or other serial interface device to the computer. serial transmission A system in which the bits of character occur serially in time; implies a single transmission channel. server A LAN component that provides shared resources to the network users. Servers are identified by the type of resource they provide. See also file server and printer server. service access point identifier (SAPI) Part of the layer 2 (LAPD) address that identifies frames to/from a particular service. service and equipment record List of equipment billed to customers by type, quantity, monthly charge, location and billing dates. service area A specific geographic area serviced by a telecommunications provider. service bureau Data processing center that does work for others, such as timesharing. service code A code, usually of the X11 series, such as 911 or 411 which customers use to access telephone services. service order A customer request for service or equipment with a vendor or carrier. service organization Local independent companies or manufacturers that contract to provide support for equipment supplied by different vendors. service terminal Equipment required to terminate a channel and connect to the phone equipment or customer terminal. servo Short for servo mechanism, an electromechanical device that uses feedback to provide precise starts and stops for such functions as the motors on a tape drive or the moving of an access arm on a disk. session 1. Connection between two devices or stations that permits them to communicate. 2. Time interval during which a terminal user can communicate with an interactive system. Session Layer The layer in the Seven Level OSI Reference Model that is responsible for adding control mechanisms to the data exchange. setup The black reference level of an input video signal. Adjusting the setup controls the level of black in a picture. SF signaling See single-frequency signaling. SFT Simple File Transfer. SGML Standard Generalized Markup Language. SGMP Simple Gateway Monitoring Protocol. shadow mask The most common type of color picture tube in which the electron beam is directed through a perforated metal mask to the desired phosphor color element. shannon equation A formula for determining the maximum rate of transmission for binary digits based on signal-to-noise ratio and bandwidth. shared tenant service (STS) A private system that concentrates and routes the local and long-distance calls of building tenants or other unaffiliated user groups, based on reselling of common carrier services. May also provide LAN, PBX and other value-added communications services to such user populations. shear A tool for distorting a selected area vertically or horizontally. sheath The outer jacket surrounding copper and fiber cables that prevents water damage to the cables inside. sheetfed A scanner design in which the original document is transported past a stationary scanning head. sheetfeeder A device that holds many sheets of paper and delivers them individually into a scanner or printing device. Also called autofeeder or automatic document feeder - ADF. SHF See super high frequency. shielded pair Two insulated wires in a cable wrapped with metallic braid or foil to prevent interference and provide noise-free transmission. shielded twisted-pair (STP) Twisted-pair cabling covered with a protective casing to help prevent data transmission errors caused by electro-magnetic fields. short code address (SCA) See abbreviated dialing. short haul Circuits designed for use over distances of 10 to 200 miles. shutdown A complete termination of computer software and/or hardware. SIAM 1. Society for Industrial and Applied Mathematics. 2. System Integrated Access Method (Unisys). sideband The frequency band above and below the carrier frequency that is produced as a result of modulation. sidestream network management A method of controlling and diagnosing networks that relies on the modems and multiplexers to monitor the various components in the analog portion of the network. Some can also check the digital facilities. sidetone Telephone equipment in the handset that permits a user to hear his or her own voice while talking on the telephone; typically used to verify that the phone is functioning. signal Aggregate of waves propagated along a transmission channeland intended to act on a receiving unit. signal computing system architecture (SCSA) An industry standard architecture from Dialogic Corp. SCSA is an open, non-proprietary, specification for developing IVR systems that integrates multiple technologies. signal control See audible signal control." signal element Each part of a digital signal, distinguished from others by its duration, position, and/or sense. Can be a start, information, or stop element. signal-to-noise ratio (S/N) Relative power of the signal compared to the noise in a channel measured at a given time; usually expressed in decibels. signaling The transmission of address and other switching information between stations and central offices and between various central offices. signaling converter A device with input and output signals that contain the same information but employ different electrical systems for transmitting that information. Used at the terminal of a trunk to convert the equipment signals to the system used on the trunk. signaling, in-band A type of signaling using an AC signal (usually 2600 Hz) within the normal voice band. This signal can be transmitted from end to end of a long voice circuit without an intermediate signaling equipment. Since the signaling is audible, the signaling equipment must be arranged for tone-on-when-idle operation. signature A uniform number built into hardware or software for identification. silver Common precious metal, the light-sensitive salts of which are used in photographic reproduction. Simple mail transfer protocol An Internet standard for transferring E-mail from host to host. Simple Network Management Protocol (SNMP) A TCP/IP protocol used for standard network management. SNMP allows network users to manage from a single workstation all devices on the network that support the protocol. simplex (SX) signaling Signaling using two conductors for a single channel. A center tapped coil or its equivalent is used at both ends for this purpose. simplex circuit See channel. SIMSCRIPT Programming language utilized for discrete simulation. simulation A model that uses physical and mathematical quantities to portray a real-life situation, such as an automatic computer used as a model for a chemical process. simultaneous voice and data transmission Ability of a telephone set to simultaneously transmit voice and data signals. single channel per carrier (SCPC) A high-speed, satellite data communications system using digital encoding and phase-shift keying (PSK) to handle larger data volumes in narrower bandwidths than FM transmissions. single threading Completes all programs or messages before starting the next one. single-digit dialing An accelerated version of speed dialing that allows a preselected group of stations to be reached by using a single digit. single-frequency signaling A signaling system that uses a 2600Hz in-band signal on the voice path. The tone is on in the idle condition, pulsed for dialing, and off when the circuit is in use. single-mode fiber Optical wave guide that carries only the single wavelength chosen for transmission. single-sideband transmission Transmits one sideband and suppresses the other; the main carrier wave may be either transmitted or suppressed. sink Portion of a communications system that receives or accepts information from a transmission device. SIO Serial Input/Output. SIOC Serial Input/Output Channel. skew 1. The misalisgnment of a document or punched card in the feed tray or hopper that prohibits it from being scanned or read properly. 2. The difference in regularity between the received and transmitted page. 3. A change of timing or phases in a transmission signal. SL System Language (various manufacturers). slave station In a data communications network, the station that is selected and controlled by a master station; the slave station can usually only call or be called by the master station. SLCC See Subscriber Line Carrier Circuit. sleeve Tubular covering, such as lead, plastic, bronze or copper used over splices, cables or outer contacts of switchboard plugs. SLEUTH Assembler (Unisys). SLIB Subroutine library. SLIP See serial line interface protocol. slotted ring A LAN architecture in which a constant number of fixed length slots (packets) circulate continuously around the ring. A full/empty indicator within the slot header indicates when a station can place information into the slot. SLU Secondary Logic Unit. SMAC Storage Multiple-Access Control. SMAE Systems Management Application Entity. smart bridges Bridges that have the necessary intelligence to identify address locations for packet filtering. smart hub A twisted-pair concentrator used in Ethernet or ARCnet networks. A smart hub has built-in network management facilities that allows a network manager to control and monitor the network performance, as well as to plan network configuration. smart terminal See intelligent terminal. SMB Microsoft's Server Message Block protocol. SMDR See station message detail recording. SMDS See Switched Multi-megabit Data Service. SMF Systems Management Facilities (IBM). SMG See supermaster group. SMP Symmetrical Multiprocessing. SMR Specialized Mobile Radio is the analog, dispatch-oriented, shared trunked radio system that subscribers pay a fee for using their mobile and portable two-way radios on the operators infrastructure and spectrum. SMTP See Simple mail transfer protocol. SNA See Systems Network Architecture. SNADS SNA Distribution Services; IBM's protocol that allows distributing electronic mail and attached documents between PCs and terminals connected to an IBM mainframe. SNAP System Net Activity Program (Unisys). SNMP Simple Network Management Protocol; a widely used protocol that provides the specification and formats for collecting network management data. SNMP is an alternative to CMIP. SNOBOL String-Oriented Symbolic Language. SNR See signal-to-noise ratio. soft font A set of characters for a particular typeface that is stored on the computer's hard disk or printer's hard disk and downloaded to the printer before printing. Soft WORM An optical WORM technique that uses rewritable technology to prevent data from being altered. software engineering A disciplined approach to the definition, development, testing, and documentation of software systems, using defined methods and procedures. SOH SONET overhead. SOL Source/Object Library. solid-state Pertaining to the use of semiconductors rather than electromechanical relays and electron tubes. SONET See synchronous optical network. SOP Standard operating procedure. source In video, the originating tape or deck. The origination point in a video editing system. Usually consists of rough-cut footage or computer-generated images. source data automation A method for reusing recorded, coded data. source document 1. The document from which a linked object in OLE originates. 2. The paper form onto which data is written. source routing IBM's alternative routing algorithm. space 1. An impulse that, in a neutral circuit, causes the loop to open or causes absence of signal. In a polar circuit, it causes the loop current to flow in a direction opposite to that for a mark impulse. A space impulse is equivalent to a binary 0. 2. In some codes, a character that causes a printer to leave a character width with no printed symbol. space segment In satellite communications, this is the space section or portion of an undertaking, compared with the earth or ground station segment. space-diversity Method of transmission and/or reception that reduces signal fading by employing two antennas on a signal tower, one below the other. space-division multiplexing (SDM) Transmission of signals over discrete voice paths. space-division switching 1. a method whereby a switch utilizing a physically separated set of matrix contacts is used to determine single transmission path routing. 2. The switching of inlets to outlets using space division techniques. spam The Internet's junk mail, e-mail that is indiscriminately sent to many users not known by the sender. spanning tree algorithm (STA) The standard for bridge-to-bridge communications, IEEE 802.1, makes it possible for routes to be automatically updated as an organization adds or deletes bridges from a network, as well as allowing bridge products from different vendors to communicate. spanning tree protocol (STP) Transparent bridging protocol, usually for Ethernet to Ethernet. SPARC Scalable Processor Architecture (Sun Microsystem). SPC See stored program control. SPD Standard Program Device. speakerphone For handsfree operation, this is a telephone that has a built in speaker and a microphone. special character Character that is neither alphabetic nor numeric. special-purpose computer Computer designed to manage only a certain function or specific range of problems. specialized common carrier (SCC) A company providing special or value-added communication services. See also value-added network. spectrum A continuous range of frequencies, usually wide in extent, within which waves have some specific common characteristic. speech circuit Circuit designed for analog or encoded speech transmission, which can be used for data or telegraph transmission as well. speed number A 1, 2, 3, or 4 digit number that replaces a 7 or 10 digit telephone number. These numbers are programmed into the switch in the carrier's office or in the PBX. speed-dialing A feature that enables a PBX or PBX station to store certain telephone numbers and dial them automatically when a short (1-, 2-, or 3-digit) code is entered. SPF Structured Programming Facility (IBM). SPI 1. Shared Peripheral Interface. 2. Single-Processor Interface. split access to outgoing trunks Two separate groups of outward dialing trunks that can be accessed by dialing the same trunk access code. splits In OCR, character bitmaps that are broken into pieces when the original document is degraded or light, or the scanner's threshold is set too high. splitter An analog device for dividing one input signal into two output signals or combining two input signals into one output signal. Used to achieve tree topologies in CATV or broadband LANs. splitting -- one-way automatic or manual An attendant can consult privately without any other party hearing; divides a cord circuit into two parts. spoofing The retransmission, alteration and interception of a cipher signal or data. spool Simultaneous Peripheral Operations On-Line. Another word for a queue; data is sent to a spool to wait to be printed or stored. spooler The software that holds queued data waiting for the availablity of a printer. spooling Technique in which output to slow devices (e.g., printers) is placed in a RAM storage queue to await transmission, leaving the user free to access the system while waiting for data to be printed. spot beam antenna Satellite antenna able to concentrate on a limited portion of the earth's surface. spread spectrum A transmission technique in which the message is transmitted in a bandwidth considerably greater than the frequency content of the original message. spread spectrum communications The process of modulating a signal over a significantly larger bandwidth than is necessary for the given data rate for the purpose of lowering the bit error rate (BER) in the presence of strong interference signals (i.e., low signal-to- noise ratio). See shannon equation. SPS Symbolic Programming System (IBM). SPUR Source Program Utility Routines. SPURT Assembler (Unisys). SPX See Sequenced Packet EXchange protocol. SQE Signal quality error. SQL 1. Sequenced Query Language. 2. Structured Query Language. A language used to query and process data in a relational database. SQL engine A program that accepts SQL commands and accesses the database to obtain the requested data. User's requests in a query language or database language must be translated into an SQL request before the SQL engine can process it. SQL/DS SQL/Data System. A full-featured relational DBMS from IBM for VSE and VM environments that has integrated query and report writing facilities. SRAM See static random access memory. SRB Source route bridging, a bridging protocol most commonly used for token-ring to token-ring. SRF Software Recovery Facility. SRT Source route transparent; translational bridging protocol, usually for Ethernet-to-token-ring connections. SS7 A common-channel signaling protocol between switching systems. SSB Single sideband. See single-sideband transmission. SSCP See systems services control point. SSDD Single Sided, Dual Density. SSI Small-Scale Integration. SSN See switched service network. SSP System Support Processor. SSSD Single Sided, Single Density (diskette). ST Start (indicates termination of outpulsing). STA Spanning tree algorithm; the standard for bridge-to-bridge communications, IEEE 802.1, makes it possible for routes to be automatically updated as an organization adds or deletes bridges from a network, as well as allowing bridge products from different vendors to communicate. stable state In a trigger circuit, a state in which the circuit remains until the application of a suitable pulse. STAG Europe's Standards Promotion and Application Group. staging In a document retrieval from an optical jukebox, the process where the image is fetched from the server by the software, and stored on the user's local PC until it is used. STAIRS Storage and Information Storage and Retrieval (IBM). STAIRS/VS Storage and Information Storage and Retrieval/Virtual Storage (IBM). standalone Any device that functions independently. star coupler A fiber-optic coupler in which power at any input port is distributed to all output ports. star network A network topology in which each device is directly connected to a central node. star topology Concentrates data processing capabilities in a centralized hub, or server, that serves as the focal point of connection for all devices on the network. StarLAN AT&T's local area network that transmits data at 1M bits per second over unshielded twisted pair wires. start bit See start element. start element The first element of a character in certain serial transmissions; used to allow synchronization. In Baudot teletypewriter operation, it is one space bit. start/stop transmission Asynchronous transmission in which each group of code elements corresponding to an alphabetical signal is preceded by a start signal to prepare the receiving mechanism for the reception and registration of a character, followed by a stop signal to bring the receiving mechanism to rest in preparation for the reception of the next start signal. See also asynchronous. static information In OCR, describes the general knowledge sources - dictionaries, syntax rules - that apply to all documents. See dynamic information. static random access memory (RAM) Random access memory that retains recorded information even after main power is switched off, by using a battery that supplies the minimum current necessary to refresh the system. static routing In static routing, the network manager configures the routing table. Once set, the paths on the network never change. station One of the input or output points of a communications system (e.g., the telephone set in the telephone system or the point where the business machine interfaces the channel on a leased private line). station address Group of numbers and/or letters that uniquely identify a station on a network. Data transmitted to a station uses the station address as a destination address, while a message transmitted from a station uses the station address as the source address. station busy lamps See busy lamp field. station busy override Telephone with the ability to override a busy signal and break into a conversation. station busy-out See attendant station busy-out. station camp-on Telephone that can queue onto a busy line; typically signals the busy station that there is a call waiting. station equipment Telephone equipment and services provided to subscribers. station hunting Calls are routed to an idle station in a prearranged group when the station dialed is busy. station loop The wiring between a station and the switching device (e.g., between a telephone set and PBX). station message detail recording (SMDR) Computer-generated records of all calls originated and/or received by a PBX station or stations. Definition is changing to refer to the RS-232-C port on the back of most modern PBXs. Also called automatic message accounting and call detail recording. station message registers Counting devices that centrally record each station's outgoing calls. station override security Shields specific telephones from executive override. station rearrangement and change Permits a user to move telephones, alter features and/or restrictions designated to certain stations and/or initiate other features. station release See automatic station release. station tone ringing An electronic, rather than mechanical bell, on a telephone. station transfer security If a call is transferred to one telephone and then another, and still not answered, this feature automatically routes it back to the attendant. station-to-station camp-on See camp-on. station-to-station dialing Any directly dialed telephone call. statistical multiplexing Technique of multiplexing a channel to simultaneously process multiple data communications transmissions; a channel is assigned to a communications device only if it actually has data to send or receive. statistical time division multiplexers (STDM) Characterized as variable allocation systems that share the resources of the digital high-speed link with the terminal devices on an as-needed basis; STDMs operate on the premise that communications links between computers and terminals are rarely utilized 100 percent of the time; STDMs use real-time statistics to allocate capacity on the high-speed link only to those terminals that are actively sending information. status indication See line status indication. STD See subscriber trunk dialing. STDM See statistical time division multiplexers. step call After dialing a busy number, a caller can place a call to a nearby idle phone by dialing an additional digit. step-by-step exchange (SXS) An electromechanical type of central office that uses switching steps working one after another, independently of the state of the following steps. STG Scale To Gray. Using gray pixels to fill in jagged edges of document images. sticky notes The ability of a document imaging system to allow annotations to scanned documents in text boxes. stitching Combining multiple strips of an image captured with a hand scanner into a single large image. stochastic network See nondeterministic network. stochastic screens Halftone screens, produced by imagesetter Raster Image Processors (RIPs), made up of randomly spaced equal-sized (small) dots instead of traditional grid-aligned dots. stop bit In a serial transmission, the last bit that provides subsequent detection of the start bit of the next asynchronous transmission. The bit length may be 1, 1.42, or 2 mark bits. stop element The last element of a character in asynchronous serial transmissions; used to ensure recognition of the next start element. In Baudot teletypewriter operation it is 1.42 mark bits. storage and retrieval system An imaging system implemented to allow users to search and gather large numbers of documents. See workflow system. storage fragmentation Inability to allot real storage locations to virtual addresses because available spaces are smaller than the page size. storage media The devices onto which data is recorded. Refers to disks, tapes, and bubble memory cartridges. storage protection A facility that prevents data or programs from being inadvertently placed over one another and/or destroyed by limiting access to the storage device or by restricting read/write access. store-and-forward The technique of receiving a message, storing it until the proper outgoing line is available, then retransmitting it, with no direct connection between incoming and outgoing lines. Also called line-switching and message switching. stored program control (SPC) A technique that programs the memory of a common controlled switching unit to provide processing instructions relating to class marks, code conversions, routing, and trouble analysis. storyboard The video editing worktable, where video, audio, and graphics clips are put into order; video effects and transitions are added; and audio editing is done to create a finished video production. STP 1. Spanning Tree Protocol; originally developed by Digital Equipment, optimizes data transmission by sending information destined for a particular workstation over multiple paths. 2. Shielded Twisted Pair Cable. STR Synchronous Transmit-Receive. straightforward outward completion Allows an attendant to place an outgoing call for a station user by dialing O or through an intercept arrangement, without requiring the station user to hang up and redial the operator. streaming tape A high-speed magnetic tape drive that is used to make backups of an entire hard disk. strobe A video effect which gives the impression that an image is moving in fixed steps by displaying on every nth frame and repeating it n-1 times. stroke One line segment in a vector graphic image. stroke edge An OCR term. The line of discontinuity between a side of a stroke and the background, obtained by averaging, over the length of the stroke, the irregularities resulting from the printing and detecting processes. stroke speed In facsimile systems, the number of times per minute that a fixed line perpendicular to the direction of scanning is crossed in one direction by a scanning or recording spot. In most conventional mechanical systems, this is equivalent to drum speed. In systems in which the picture signal is used while scanning in both directions, the stroke speed is twice the above figure. stroke width In character recognition, the distance measured perpendicularly to the stroke centerline between the two stroke edges. structure A graphic notation that describes the physical structure and partitioning of a system. Structure charts are the graphic notations used in the structured design methodology. structured analysis A graphically oriented technique used to specify system requirements. Structured analysis is used in the first stage of a design cycle to ensure completeness and consistency in aspecification. Using structured analysis, designers can develop an accurate and complete system specification before the design phase begins. structured design A graphically oriented technique used to develop the physical partitioning of system functions. Structured design usually follows structured analysis and uses the data and process definitions defined during structured analysis to ensure consistency between the logical model of a system and its physical model. STS See synchronous transport signal. STS-1 See synchronous transport signal-level 1. stunt box A device to control the nonprinting functions of a teletypewriter terminal, such as carriage return and line feed. STX Start of text (of message). stylus Pen-like instrument used with a graphics tablet as an input device. subchannel The result of subdividing a communications channel into narrower bandwidth channels. See also bandsplit. Subnet A portion of a network partitioned by a router. subprogram A program that is implemented by another program. subroutine Software that performs an often-used function. subscriber line Telephone line that connects the local telephone company to the subscriber's telephone system or medium. Subscriber Line Carrier Circuit (SLCC) A system that allows one pair of copper wires to carry multiple conversations. SLCC is used between Central Offices and areas that have outgrown the cable that has been placed to serve that area. subscriber loop Circuit, usually a pair of wires, that links the CO to the demarcation point on the customer's property. subscriber trunk dialing A non-American term for direct distance dialing. subsystem Secondary system able to work independently or asynchronously with the primary system. subtractive color A theory that explains color as the reflection of light by colorants or pigments. As the primary colors of cyan, magenta, yellow are combined, there is a reduction in the amount of light reflected. subvoice-grade channel Channel of narrow bandwidth unable to manage voice communications, usually used for slow data communications and teletype. super high frequency (SHF) Frequencies ranging from 3GHz to 30GHz. supered graphic A graphic superimposed over the video. supergroup The assembly of five 12-channel groups, occupying adjacent bands in the spectrum, for simultaneous modulation or demodulation. supermastergroup (SMG) 600 circuits processed as a unit in a carrier system. superservers Based on Intel's i486 microprocessor chip and RISC architecture, these servers provide exceptional error detection capabilities. They are equipped with multiple processors and a mainframe-like I/O structure that eliminates bottlenecks associated with traditional file servers. supervision In telecommunications, the process of detecting a change of state between idle and busy conditions on a circuit. supervisory control Signals that automatically drive equipment or indicators at a remote terminal. supervisory lamp See busy lamp field. supervisory signals A signal such as on-hook or off-hook, that indicates whether a circuit or line is in use. surface modeling A CAD technique for representing solid objects. SVGA Super Video Graphics Array or Super VGA. SVID System V Interface Definition (AT&T UNIX). SVS Single Virtual Storage (IBM). SVVS System V Verification Suite (AT&T UNIX). SWADS Scheduler Work Area Data Set (IBM). sweep In graphic design, this tool takes a two-dimensional shape and sweeps around an axis while scaling the shape, creating a final object. It is used to create objects such as a nautilus shell. swim Slow, graceful, yet undesired movements of display elements or images about their mean position on a monitor. Swim can be followed by the human eye, whereas jitters usually appears as a blur. switch Equipment used to interconnect lines and trunks. switch, intelligent See intelligent switch. switchboard A term originally defining manual equipment that performed switching functions and now commonly applied to the attendant position for a PBX. switched access transport services The transportation of switched traffic along dedicated lines between the local telephone company's central offices and the long distance carriers points of presence. switched Ethernet An Ethernet network that runs through a high-speed switch. The switch is capable of handling hundreds of megabits per second; each user receives the full 10 Mpbs Ethernet bandwidth. switched line A communications link for which the physical path may vary with each use (e.g., the dial-up telephone network). switched line A link that is established in a switched network, such as the international dial-up telephone system, a Switched 56 digital line or ISDN. switched loop operation Each call needing attendant assistance is automatically switched to one of several switched loops on an attendant position. Switched Multi-megabit Data Services (SMDS) Bellcore's prototype network-based service that provides high levels of data throughput and network availability. SMDS is designed to take advantage of evolving MAN standards and technology that telephone companies can deploy to provide cross-premises communications services. With SMDS, a customer can send a packet of information over a dedicated interface operating initially at the DS3 rate (44.736M bps) to the nearest switching office equipped with a high-performance packet switch. switched network See public switched telephone network. switched service network (SSN) Private line network that utilizes scan and/or CCSA-like common control switching. switched virtual call (SVC) Call established only for the duration of a session. switching The operations involved in interconnecting circuits in order to establish communications. switching center A center where messages are stored and processed for transmission to the intended destinations. Computers provide the communications functions of routing, priority processing, code and speed conversion, and transmission in addition to their other functions. switching hub A device that acts as a central switch or PBX, connecting one line to another. In a local area network, a switching hub gives any two stations on the network the full bandwidth of the line. switching matrix In a space division exchange, a group of crosspoints which operates as a traffic switch. See also matrix. switching office A telephone company office that contains a switch. switchook See hookswitch." switchover When an equipment failure occurs, an alternative system (e.g., file unit, communications line, or computer) can be manually or automatically activated. SWOP Specifications Web Offset Publications. A standard for representing process colors printed on offset printing presses. SX signaling See simplex signaling. SXS See step-by-step exchange. Symbiotic service element A group of functions that supports the operation of another service element by adopting its semantics. symbolic language Language written in human understandable form rather than machine language. symmetric multiprocessing A multiprocessing design in which any CPU can be assigned any application task. One CPU acts as a control processor booting the system, distributing work to the next available CPU, and managing I/O requests. sync character Character transmitted to fix character synchronization in synchronous communications. synchronization Technique of regulating the corresponding significant instants of two signals to obtain the desired phase relationship between these instants. synchronous Having a constant time interval between successive bits, characters, or vents. Most mainframes use synchronous communications. synchronous communications Technique that transfers serial binary data between computer systems or systems and peripherals. synchronous data switching Facility to transmit synchronous data using a synchronous data adapter; data transmission in which the transmitter and receiver have a fixed time relationship. synchronous network Network in which all communications connections are synchronized to a shared clock. synchronous optical network (SONET) Approved standard for high- speed synchronous network. synchronous transmission The serial transmission of bit streams in which each bit occurs at a fixed time interval and the entire stream is preceded by a specific combination of bits that initiates the timing. synchronous transport signal (STS) A SONET electrical signal rate. synchronous transport signal-level 1 (STS-1) An electrical signal that is converted to or from SONET's optically based signal; equivalent to the OC-1 signal of 51.84M bits per seconds. syntax error Error caused by incorrect programming statements in the context of the language being used. SYSGEN System generator program. SYSLOG System log. system 1. A group of related components that interact to perform a task. 2. The CPU, operating system, and peripheral devices of a comuter system. 3. The database, all the data entry, update, query and report programs, and manual and machine procedures of an information system. 4. The operating system. system administrator A person who manages a multiuser computer system with responsibilities similar to those of a network administrator. system development cycle The sequence of events in the development of an information system. system development methodology The formal documentation for the phases of the system development cycle. These include the precise objectives for each phase and the results required from a phase before the next one can begin. system disk A hard or floppy disk that contains part or all of the operating system or other control program. system failure A hardware or operating system malfunction. system file A machine language file that is part of the operating system or other control program; may also refer to a configuration file used by such programs. system folder The operating systm folder in the Macintosh that contains the System, Finder and MultiFinder, printer drivers, fonts, desk accessories, INITs, and cdevs. system font The primary font used by the operating system or other control program to display messages and menus unless otherwise directed. system life cycle The useful life of an information system. Its length depends on the nature and volatility of the business and the software development tools used to generate the databases and applications. system log File or data set where job-related and operational information, descriptions of unusual happenings, commands, and messages to or from the operator may be stored. system memory The memory used by the operating system. system program A component of system software. system prompt An on-screen symbol that indicates the operating system is ready for a command. system reliability Probability that equipment will perform accurately under normal operating conditions. system software Programs used to control the computer and develop and run application programs. System software includes operating systems, TP monitors, network operating systems, and database managers. systems analyst The person responsible for the development of an information system. Systems Application Architecture (SAA) Comprehensive IBM specifications that describe the evolving integration of disparate IBM hardware platforms, communications devices, and system software products. systems disk A disk pack or disk drive reserved only for system software; includes the operating system, assemblers, compilers, and other utility and control programs. systems integrator An individual or organization that builds systems from a variety of diverse components. systems management 1. The management of systems development, including systems analysis and design, application development, and implementation. Systems Network Architecture (SNA) IBM's definition of the logical structure, formats, protocols, and operational sequences for transmitting information units between IBM software and hardware devices. systems programmer 1. A technical expert on some or all of the computers's system software. 2. A person who designs and writes system software. systems services control point The element of a network based on IBM's System Network Architecture that provides overall network control. The SSCP is usually a mainframe.