Fiber Optics Illustrated Dictionary of both store-and- forward and realtime facsimile pro- tocols (ITU-T T.37, T.38). spoofing, network In network traffic routing, a means of rerouting, or otherwise changing the desti- nation ofa transmission by mimicking the destina- tion through responses, signals, or other identifica- tion. Spoofing has legitimate purposes, such as test- ing and modeling, or overcoming problems of latency in slower devices, but often the spoofing is intended to gain unauthorized access to a system or to imper- sonate a system and send substituted information. Reports of malicious spoofing on the Internet began to emerge in the mid-1990s. Spoofing can be set up at the beginning ofa session or can be inserted into a session after it has been es- tablished. The first method may be harder to detect, while the second may be a means to eavesdrop on information the source system thinks it is sending to the original destination, which is now the spoofed destination. In general, the spoofing is carried out by impersonating a trusted destination IP address. The spoof can sometimes be detected if the IP address is found to originate on the local system rather than on an external system. Spoofing occurs for many reasons. It can enable a user to intercept programs or information or it can be used to send bogus responses to requests from the originating system. It can also compromise the abil- ity ofa system to carry out its normal functions. A denial of service attack is a situation in which a ser- vice (e.g., a Web server for a stock quote or online auction system) is made unavailable to normal users. By setting up a loop that ties up or floods the system, for example through a half-open connection that over- flows, denial of service can be achieved. This doesn't usually compromise the information on the attacked system, but may harm it by denying legitimate users access. The host system may not be aware of the prob- lem until customers begin to complain. Since the mid- and late-1990s, various dynamic rout- ing techniques and packet traffic monitors have aided in preventing and detecting spoofing. See Computer Emergency Response Team, Computer Incident Ad- visory Capability. spoofmg, Web site This is a subset of network spoof- ing that specifically spoofs or impersonates a Web site at another location. A vulnerability exists within browser software supporting HTML frames preva- lent in the late 1990s. Subsequent versions of brows- ers have been updated to help prevent this type of spoofing (e.g., Netscape Communicator 4.51). Web site spoofmg is usually a malicious activity in- tended to mislead, inconvenience, or harm. A Web site can be spoofed to make a site look bad (e.g., ma- ligning a commercial site) by inserting insulting, poorly designed, or shocking images or text into an otherwise normal-looking site. Spoofing can also be similar to the Trojan Horse concept wherein some- thing desirable appears to be offered (but not given) to the user in order to gain entrance to a location or information repository. The user may think he or she is getting a free product sample, for example, when 882 the spoofed site is actually capturing names and mail- ing addresses (in fact this type of fraud can be car- ried out on a nonspoofed site, as well). Not all Web site spoofs exploit browser vulnerabili- ties. Some of them rely upon human trust and error. One type of Web spoof impersonates the layout and functions of another Web site and mayor may not spoof the original IP address or domain name (Web sites are sufficiently high in information content that an IP address or domain name change may not be no- ticed by the user). F or example, in summer 2000, someone spoofed the login page for the PayPal online financial system, which enables users to conduct online monetary transactions through user accounts. The Web page was designed to clandestinely capture names and passwords. The perpetrators then sent out bulk email that looked like a legitimate PayPal notification with a clickable Web address embedded in the email mes- sage. However, the embedded URL didn't link to www.paypal.com, it linked to www.paypaI.com with a capital "i" rather than a lowercase "1". People couldn't easily see the deliberate misspelling and anyone who linked to the site and tried to log on gave away his or her login name and password. This could then be used to access the real PayPal account to en- able the perpetrators to transfer funds. Fortunately, the fraud was discovered quickly, before significant harm was done. This kind of spoofing has a good chance of landing the perpetrators in jail. spool v. An acronym for "simultaneous peripheral operations on line," a means of running scanners, printers, plotters, video capture systems, or other peripherals while other computing tasks are ongoing. In earlier nonmultitasking computer systems the ac- ronym was misleading, since spooling was a way of saving information in a file so it could run as a batch job later, rather than as a simultaneous process. Spool- ing as we know it now more accurately reflects the acronym. It is a technique for improving efficiency by accommodating the different operating speeds of a number of types of peripherals and processes by scheduling and optimizing the exchange of hand- shakes and data transmission. Spooling is especially popular for creating files that will be printed as a background task or sometime later (e.g., overnight, when printers aren't so busy, or when the computer isn't engaged in CPU-intensive functions). On multitasking systems, it is not necessary to wait for a print, plot, or other peripheral job to finish to continue word processing or drawing, but it may slow current processes. Thus, the system may schedule the printing job to run while the user is away from the keyboard or engaged in computing tasks requiring less processing power. The resource management software routines can be designed to sense when re- sources are available and carry out the print job. On single-tasking or task-switching systems, however, with peripherals that don't support a queuing system, wait time can be a problem while a file is processed or printed. For example, plotters tend to print rather slowly. If the user must wait for 25 minutes while a © 2003 by CRC Press LLC plot is created, productivity is lost. By sending the plot to a software spooling process (or a hardware spooling buffer) and plotting it at a convenient time, the user can continue working uninterrupted. spot of Arago In 1818, Augustin Fresnel, after whom the Fresnel lens is named, submitted a thesis on dif- fraction to a competition sponsored by the French Academy of Science. At the time, the wave theory of light was not scientifically accepted and Simeon Pois- son endeavored to shoot down Fresnel's thesis on the basis that his theory would predict that a bright spot would appear in the shadow behind a circular obstruc- tion. Dominque Arago, a member of the judging com- mittee, took the time to try the experiment and veri- fied Fresnel's prediction. It is sometimes called Poisson's bright spot, but it is more fitting that it be called the spot of Arago. See diffraction; Fresnel, Augustin. spread spectrum A technique used with radio-fre- quency-generating systems to spread the emitted wavelengths over more than one frequency, in either predefined or random patterns (or a combination of these). In telecommunications, spread spectrum is generally divided into frequency hops, a system de- veloped over 50 years ago by Hedy Lamarr, and di- rect sequencing, which utilizes the noise-like char- acteristics of pseudorandom sequences to control a phase modulator. At the sending end, specific types of noise are incor- porated into the signal, which is spread over a wider frequency range. At the receiving end, a lower band- width version of the original signal is recovered. Spread spectrum is used for a number of reasons: it can reduce overall interference with other radio sig- nals, can be more difficult to detect, intercept, or de- code, and more difficult to jam, thus providing sev- eral types of security not possible with single-fre- quency transmissions. There are tradeoffs when us- ing spread spectrum. More bandwidth than normal is required to transmit the signal. Spread spectrum broadcasts are not only used in co- vert or private communications, but are now also used as a means to optimize increasingly limited broad- cast space due to increased demand. In the United States, unlicensed spread spectrum transmitters are permitted to broadcast within specified frequency ranges. As an example, the 900-MHz cordless tele- phones and a number of wireless local area networks (LAN s) operate in the unlicensed spread spectrum frequencies. Pseudonoise, or direct sequence spread spectrum, is a technique used in local area wireless networks (LAWNs). Redundant data bits called chips are in- corporated into the transmissions and the receiver must have knowledge of the spreading code to re- move the added chips and decipher the incoming mes- sage. The insertion of chips provides a means to pro- vide more frequencies within a given area, with a tradeoff in speed. The throughput of this type of sys- tem is about 2 to 8 MHz. The Federal Communications Commission (FCC) regulates the amount of time that may be spent on anyone channel. For example, in the ISM band of 902 to 928 MHz, the frequency hop on a particular channel must not exceed 0.4 seconds once every 20 seconds. Similarly, in the 2.4- to 2.484-GHz range, the interval is not more than once every 30 seconds. Recommendations are also being drafted by the IEEE. See frequency hopping, spread spectrum clocking. spreadspectrum clocking In electronics, many com- ponents emit radiation. The smaller and more tightly these components are bundled, the more likely there is to be undesirable electromagnetic interference (EMI) from neighboring parts. This is especially true in precision very large-scale integration (VLSI) elec- tronic components generating high clock frequencies. Spread spectrum clocking is a means of spreading the spectral emissions generated by the clock signals to reduce the overall EMI. This is often done through frequency modulation (FM). See spread spectrum. spreading loss In a beam ofradiant energy, loss as- sociated with the geometrical spread of the energy as distinct from absorption and scattering. Thus, the peak power level that emanates from the energy source is reduced as the energy propagates outward. It is also known as energy spreading loss (ESL). To better understand this, imagine the light from a flashlight beam gradually spreading as it travels away from the source. When the beam hits the upheld palm of a friend standing several feet away, the strength or power of the light is lower than if the palm is in front of the light a few inches away. The rest of the light will spread around the palm, passing it by, even ifno absorption or other type of loss occurs. Acous- tic energy, like electromagnetic energy, exhibits spreading loss, because it radiates outward, which makes spreading loss an important consideration in sonar technologies as well. When spreading loss occurs in energy forms travel- ing through the air, it may be termed free air loss. Spreading loss can vary as frequencies vary and as frequency compositions vary. For example, spread- ing loss in a coherent beam oflaser light is far less than the spreading loss in a beam from a flashlight. Spreading loss becomes greater as the distance from the source increases (e.g., a radar echo traveling to- wards a target will exhibit spreading loss not only on the way to the target but also on the way back). It is especially important to account for spreading loss in very remote sensors, such as satellite imaging systems. Range-spreading loss associated with satellite imag- ing sensor data may be compensated for, based upon distance, incident angle, and known characteristics of the sensing medium. Some commercial satellite image products are routinely processed for range- spreading loss (e.g., synthetic-aperture radar products). In fiber optic transmissions, spreading loss is reduced or mitigated in a variety of ways, including reducing the number of components and installing active re- lays. Spreading loss in a number of media can also be compensated for by redirecting the spread energy back into the main beam. See absorption, attenuation, scatter. 883 .'::.~. lJ © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Sprint A well-known telecommunications services company, Sprint was one of the early companies to make dialup access to nationwide ISPs affordable, in the early 1990s. Sprint began as a small telephone company in Abilene, Kansas, founded by Cleyson L. Brown, in 1899. The Brown Telephone Company provided an alternative to the Bell system and grew and was re- organized as United Utilities. By the 1950s, it was the second-largest non-Bell company in the U.S. In 1972, the name was changed to United Telecommu- nications. By the late 1970s, the company began in- stalling fiber optic links and soon after established UNINET, then the third largest commercial packet data network in the world. In the mid-1980s, Sprint became known for its long-distance services. Sprint established the first coast-to-coast, national fiber optic data and telephone system as Sprint International af- ter which United Telecommunications became Sprint Corporation, in 1992. In 1995, Sprint moved into the mobile market by ac- quiring wireless licenses for 29 major trading areas auctioned by the Federal Communications Commis- sion (FCC). In 1998, Sprint introduced ION, simul- taneous voice, video, and data services over existing connections. There was an unsuccessful attempt to merge Sprint and WorldCom, a merger that did not receive U.S. government approval. Thus, Sprint focused its efforts upon building Sprint PCS into a major wireless ser- vices vendor. SPS See Standard Positioning Service. spud bar A tool somewhat resembling a cross be- tween a pry bar and a long-handled, short-bladed spade. The handles may be D-shaped or ball-shaped and the blades may be replaceable. These are useful for breaking up tough soil clots for installing utility poles in areas where it is not practical or possible to bring in mechanized diggers (they're also handy for scraping asphalt lumps and old roofing or siding ma- terials and for making holes in thinner patches of ice). spur 1. A foot spike worn by line workers to improve contact and traction when manually climbing utility poles to carry out maintenance, testing, or repair. 2. A tributary or offshoot from a main line, as in a rail- road track or communications spur line. Spur lines may run to the end of a cuI de sac, a pier, or other tenninal point where there is an obstruction or no fur- ther need for the line to continue. Sputnik I The world's first artificial satellite, launched by the Russian Federation on 4 October 1957, studied the ionosphere and heralded the space age. It transmitted in a frequency range just above global frequencies for standard time signals, so that those listening in, which included Earth stations all over the world and a large number of amateur enthu- siasts, would be able to monitor and report the status of the satellite. The project was announced in print by the Russian Federation several months before its launch so that results of communications from the sat- ellite could be reported. See Radio. Sputnik 2 The world's first successful launch and 884 retrieval of a living creature, Laika, a dog, was car- ried out by the Russian Federation in Sputnik 2 on 3 November 1957. This craft also studied space radia- tion and used a slow-scan TV camera to relay images to the ground. sputtering See magnetron sputtering. SQL Structured Query Language. A widely used, structured data sublanguage coding system for que- rying database infonnation ( e.g., Oracle). Most pro- fessional database programs support SQL- format files or can import/export SQL instructions. SQL emerged from technical descriptions of relational databases documented by computing professionals such as E.F. Codd. Based upon this model, ffiM de- veloped SEQUEL, the forerunner to SQL. In 1979, Relational Software, Inc. introduced a commercial implementation of SQL that became integral to the Oracle database program. The company later became Oracle Corporation. SQL has been supported and standardized by a num- ber ofprominent organizations, including ANSI and IS/IEC. Embedded SQL comprises SQL statements within a procedural programming language as well as certain extensions to standard SQL statements. SquareA data-securing block cipher system devel- oped by Joan Daemen and Vincent Rijmen. Paulo Barreto and George Barwood developed a fast imple- mentation of the algorithm for the Pentium II that is available on the Web. Square was used as the basis for the development of Rijndael, an important sys- tem used by the U.S. government. See Rijndael. Sr symb. strontium. See strontium. SR symb. left-hand slant polarization (ITU). SRAPI Speech recognition API. A speech recogni- tion and translation applications programming inter- face (API) developed by the SRAPI Committee, a Utah nonprofit corporation consisting of some well- known vendors of various audio and multimedia products. http://www.srapi.com/ SRGP See Simple Raster Graphics Package. SS7 See Signaling System 7. SSAC13 Signaling System Alternating Current No. 13. ABritish automatic IVF signaling system for transmitting supervisory telephone signals between private branch exchanges (PBXs) in the 2280-Hz fre- quency. Using the two-wire section of a transmission path, signals may be sent in one direction or the other (but not both at the same time), although some imple- mentations use four wires for two-way signaling. SSAC15 Signaling System Alternating Current No. 15. A British private telephone line signaling sys- tem designed to operate in the 2280-Hz frequency. Each line has two transmitting lines and two receiv- ing lines such that it is suitable for setting up a wide- area network (WAN) with two or more private branch exchanges (PBXs) and the appropriate wiring and in- terface cards. BTNR 181 is the British Telecom Sig- nal Systems SSAC 15 standards description. SSB See single sideband. SSCS See Service Specific Convergence Sub layer. SSCOP See Service-Specific Connection-Oriented Protocol. © 2003 by CRC Press LLC ST Ports & ST- Connector - Basic Parts version of ST2+ was specified for UNI 3.1 in 1998. ST2+ is anATM-based, connection-oriented Intemet protocol for communication among ST2+ agents. The protocol is designed to extend UNI 3.1/4.0 signaling functions, to reduce certain signaling limitations, and to manage resources more efficiently in ATM and non-ATM networks. The protocol specifies the inter- action between ST2+ and ATM on three planes that correspond to the lTU- T B-ISDN Protocol Reference Model: Plane Notes user Specifies encapsulation of the ST2+ DATA PDU into the AAL-5 PDU management Specifies the Null FlowSpect, Con- trolled-Load Service FlowSpec, and the Guaranteed Service FlowSpec mapping for UNI 3.1 traffic control Specifies encapsulation of the ST2+ SCMP PDU into the AAL-5 PDU, the relationship between ST2+ SCMP and PVC management (for ST2+ data), and the interaction be- tween ST2+ SCMP and UNI 3.1 signaling See byte-stream protocol, STll, RFC 2383. STU, ST2 Stream Protocol Version 2. Aconnection- oriented Internet protocol which brings together SCMP (for signaling and control) and ST (streaming protocol). A connection must be set up between ~r~~~~~&~~~~:~~~:~Ei=:!~~; i. deal oflntemet traffic is connection-oriented, in that the receiving system doesn't have to be determined to be online before atransmission is sent. ST2 has an IPv5 designation. See ST2+, RFC 1819. STA 1. See spanning tree algorithm. 2. Science and Technology Agency. Japan's research and develop- ment support, to plan and coordinate national science and technology. Founded in 1956. stage A designated platform or work area that is sometimes housed in a special enclosure or room to provide the right environment for the work to be carried out. A microscope stage is the region where the sample is held in place for viewing. A fiber optic fusion splicing stage is the region where two fila- ments are aligned and spliced. stand alone, stand-alone, standalone A system or device providing a self-contained service or function, independent ofother major components. See turnkey system. standard cellA fragile, special-purpose cell provid- ing very small amounts ofelectrical current (1.0 19V) for short periods. standard network variable type SNVT (pron. snivit) A common variables framework element ::'::~::""""""'.Y":"'''::''''''''''': : : , ":'" ~"'~, ::, :\l~~· \, 'l~~~~; . ssep 1. See Service Switching and Control Point. 2. See System Services Control Point. SSD 1. Secret Service Division. 2. Service Selection Dashboard (Cisco Systems). 3. shared secret data. Encryption infotmation shared between negotiating systems for purposes of security. In mobile commu- nications environments, SSD is divided into authen- tication procedures (SSD-A) and privacy/confiden- tiality (SSD-B) with SSD infotmation shared between a user mobile handset and an Authentication Center (AC) and sometimes also a Visitor Location Register (VLR). SSD is documented inANSI-41. SSL See Secure Socket Layer. SSP See Service Switching Point. SSRP See Simple Server Redundancy Protocol. SSTV See slow scan television. ST 1. See Scheduled Transfer. 2. signaling tetminal. 3. straight-tipped. 4. systems test. ST- ports (top) and their associated connectors are standardizedjiberoptic couplingcomponents that are widely used. The basic components in the ST- connector include (bottom image, left to right) a strain reliefboot (to prevent excessive bending), sometimes acrimp sleeve, a 2.5 mm-ferrule connector, which may have a bayo- net mount, and a dust cap. The necessityfor a crimp sleeve depends upon the clampingor bonding method. The size of the hole to accommodate the fiber varies with the diameter of the fiber to be inserted. ST- connector A common, standardized connector for coupling fiber optic cables. ST- connectors may vary in the details oftheir appearance but are essen- tially mechanically the same. They are fabricated in a variety of materials including metal (e.g., stainless steel), plastics, or ceramics. ST2+ A connection-oriented, routable, multicast- capable Intemet protocol for providing native ATM circuits for applications that require bandwidth guarantees and Quality of Service (QoS). ST2+ is an updated version of STII (ST2), specified in 1996, which has an Intemet Protocol V.5 (IPv5) designa- tion. See ST2+1UN1, RFC 1946. ST2+1UNI Stream Protocol Version 2+. An evolu- tionary descendent ofsm and a version ofa previous ST2+ providing native ATM support for ST2+, this 885 © 2003 by CRC Press LLC application program Standards that influence application portability by describing and defining interoperability between applications software and the computer operating system. Consideration is given to systems, communications, information, and human- computer interactions. platform external Standards that influence system portability and interoperability, that is, the behavior of information processes which interact with their external environment. Data portability and user interfaces are important considerations. Conformance to these standardization concepts pro- vides a framework for vendors to develop and dis- tribute products and services compatible with those of other vendors, and provides users with some as- surance that products purchased from different ven- dors will work together. standby processor A spare or secondary processor in a computer system that is ready to take over if there are problems with the first, or if extra computing power is needed on an irregular basis. The standby processor is usually a hot standby device, that is, it can come online without turning the system off or interrupting its functioning to a substantial degree. Sometimes the second processor is not idle, but is used for less intensive computing operations, while still remaining ready if it needs to come online as a substitute for the main processor. In some cases, the standby processor does low-level maintenance work on updating its databases and file structures, so that if the primary processor goes offline, the file infor- mation is known by the standby processor. Standby processors are most commonly used. in high- end systems that require a high degree ofreliability. Examples would include medical or navigational ap- plications where people's lives might be in danger if there were a processor failure. standby time 1. A power-saving feature built into many consumer electronics. Camcorders, calculators, laptop computers, and various other devices that rely on limited battery power will often have timing mechanisms that monitor idle time, that is, time dur- ing which the device receives no input from the user. When the idle time expires, the device is powered down or put in a minimal power-consuming mode, in order to save battery life. 2. The amount of time a fully charged battery-powered unit can remain on before the battery runs out. This applies to many de- vices, including cell phones, cordless phone·s, short- range radios, laptop computers, etc. Standby time is often used as a marketing statistic to characterize a system and generally refers to idle time, rather than Fiber Optics Illustrated Dictionary designed to support interoperability. The term is es- pecially associated with the LONWorks control au- tomation system, though it is applicable in a general sense to other types of network devices where pre- defmed network variables have been associated with various units within the system (e.g., degrees, meters, volts, etc.). Standard Performance Evaluation Corporation SPEC. A nonprofit organization supporing the estab- lishment and maintenance of standardized, relevant benchmark computer performance evaluation tools that can be applied to various high-performance sys- tems. http://www.specbench.org/ Standard Positioning Service SPS. One of the pre- cise location data signals transmitted from Global Positioning System (GPS) satellites. This signal is available without charge for private and commercial use and is not encrypted. It provides information about the functioning of the satellite and its approxi- mate location. Combined with infonnation from three or four other satellites, the user can pinpoint a loca- tion with horizontal and vertical accuracies up to about 100 m and 340 nsec of time, depending upon the quality and accuracy of the receiving equipment. See Global Positioning System, Precise Positioning Service. Standards Australia International, Ltd. SAl. An Australian standards organization with strong inter- national activities focused on supporting business-to- business services based on knowledge sharing. The organization was established in 1922 as the Austra- lian Commonwealth Engineering Standards Associa- tion and became the Standards Association of Aus- tralia (SAA) in 1988. Other changes were made, and the organization was incorporated as Standards Aus- tralia International in 1999. SAl generates revenues through normal business ac- tivities and government-funded contributions to the national interest. It makes innovative use of the Web to develop and distribute intellectual property. Through a large number of technical committees, a staffof almost 300, and thousands of voluntary ex- perts, SAIl maintains over 6000 standards. Standards Council ofCanada SCC. The Standards Council of Canada is a federal Crown corporation responsible for promoting efficient and effective vol- untary standards in Canada for the health, welfare, and economy of Canada. The SCC works in coop- eration with, and manages, the National Standards System. The SCC coordinates input from the SCC to the International Organization for Standardization (ISO) and the International Electrotechnical Commis- sion (IEC). See Canadian Standards Association, Telecommunications Standards Advisory Council of Canada. http://www.scc.ca/ standards reference model A communications framework for describing and classifying information processing standards by the Institute of Electrical and Electronics Engineers, Inc. (IEEE). Within the reference model, general sets of requirements are developed. The reference model divides standards into two cat- egories: 886 Interface Type Description © 2003 by CRC Press LLC time during which the item is used. The use time (or talk time on a cell phone) is typically less if many features are used. standing wave A phrase which is used to describe physical relationships and movements in real life as well as diagrammatic representations on display sys- tems such as computers and oscilloscopes. Very large standing wave patterns are described by astronomers when talking about the movement, relationships, and symmetry of galaxies. standing wave ratio SWR. A diagnostic measure- ment ofa standing wave which is commonly used in transmitter and transmission line testing and mainte- nance. When cables are affected by moisture, wear, and loose connections, an impedance mismatch may occur which can be detected through the amplitude ratio ofa standing wave. The transmitted wave is used as the signal source for measurement by an inline SWRmeter. StanfordArtificial Intelligence Laboratory SAIL. This research laboratory is the source of many pio- neer ideas and developments in artificial intelligence and general concepts related to computers. SAIL con- tributed to the development of the LISP programming language. The SAIL facility also developed the SAIL programming language, an ALGOL-like language created in the early 1970s. The SAIL facility was closed down in 1990. Stanley, William An inventor who created the first practical alternating current generator, after it was pioneered by Elihu Thomson. Thus, the first Stanley alternating current (AC) distribution system came into being in 1885, 3 years after Thomas Edison opened the first direct current (DC) power utility company. In conjunction with Elihu Thomson and Sebastian de Ferranti, Stanley also developed the transformer. See Alexanderson alternator. STAR TAP The Science, Technology, and Research Transit Access Point. This is a persistent communi- cations infrastructure project funded largely by the National Science Foundation to facilitate the opera- tion and interconnection of advanced international networking systems. It supports applications, perfor- mance measurement, and technology evaluation, and facilitates the flow of network traffic to international collaborators. The project is managed at the Univer- sity of Illinois Electronic Visualization Laboratory. See STAR TAP International Advisory Committee. http://startap.net/ STAR TAP International Advisory Committee A committee of international member groups connected to STAR TAP or interested in joining STAR TAP which oversees STAR TAP policies and operations. Members are affiliated with a wide variety of orga- nizations including CERN, SURFnet, TransPAC, iCAIR, and Euro-Link. See STAR TAP. star test In optics, a means of testing the alignment of reflecting surfaces at high powers by using illu- mination from a star as a reference. A star test typically uses the entire telescopic instrument rather than just the reflecting mirror or lens components. The pattern from a perfect optical test resembles a top view ofa dinner plate with concentric rings in different widths and light values. If the lens is misaligned or aberrant, the pattern may appear eliptical, off-center, or blurred. Since a star test is done with the full assembly, it can also be used "on the fly" to make corrections. The star test is sometimes used as a followup to the Ronchi test. See DaB test, Ronchi test. star topology A common type of network topology in which remote systems and nodes are connected point-to-point to a central system, and not to one an- other. Unlike some topologies with redundant con- nections, if the central system on a star network fails, the entire network is unable to intercommunicate. One advantage is that problems are easier to isolate, another is centralized administration and security. A star system provides the option of physically isolat- ing the server from unauthorized access. Star topolo- gies are used in many phone and data networks. See hub, topology. Stark effect An effect observed and described by Johannes Stark, in 1913, following several years of research into Doppler effects in rays. He observed the application of an electric field could induce the split- ting of spectral lines when he was studying the spec- trum of hydrogen. Further investigation indicated that the spectra decomposed into several components, some of which were linearly polarized through the influence ofa strong electric field and that this effect could be observed in substances other than hydrogen. Thus, at the atomic level, it appeared that the influ- ence of an electrical field produced different results from that ofa magnetic field. See Zeeman effect. Stark,Johannes (1874-1957) AGennan researcher who studied the influence of electrical fields on spec- trallines. Stark was awarded the Nobel Prize in phys- ics in 1919 for his discovery of the Doppler effect in certain rays and of the distortion properties of an elec- trical field on spectral lines. See Stark effect. start pulse In a start-stop teletypewriter system, a mechanism to release the receiving line relay and permit the receiving arm to move. start-stop synchronizationA method developed by Howard L. Krum for use with permutation code tele- graph systems. stateful packet filtering SPF. Packet filtering is a security and traffic management technique used in packet-based networks to selectively control network traffic based on information contained in packet head- ers. Many routers are equipped to support packet fil- tering. Dynamic packet filtering is a means of dy- namically handling the traffic management after a stream of packets has passed through, to minimize the number ofsecurity gaps that might be left open by static packet filtering. Stateful packet filtering is a form of dynamic packet filtering that applies pro- tocol-specific filtering rules and monitors state and context information associated with a network ses- sion. This may, in some cases, improve security (or appear to improve security), while still having some limitations and drawbacks associated with direct connections to internal hosts and no direct user au- thentication. See spoofing. 887 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary static n. 1. In radio transceivers or phone systems, static (also called atmospheric) is noise resulting from weather phenomena and related atmospheric electri- cal charges. Proper grounding can help reduce static interference. See interference, noise. static electricity An electrical charge at rest, famil- iar to many people as static electricity. Static elec- tricity associated with rubbing amber (amber in Greek is elektron) was known to the Greeks by at least 600 B.C. when Thales recorded that a"fossilized veg- etable rosin" (amber), when rubbed with silk, ac- quired the property to attract very light objects to it- self. See mutual capacitance. static generator An early experimental device used to investigate static electricity and its effects. Static generators still are valuable as educational tools. See static, Van de Graaf generator. static object A software term for an unchanging or uneditable object in an application or document. Im- ages are often embedded as static objects in word pro- cessed documents, and can only be edited by locat- ing the source document, changing it in the original context, and updating the static location (or reinsert- ing it into the document as a static or dynamic ob- ject). Contrast with linked object. static RAM SRAM. A type of fast electronic ran- dom access memory chip which is often used in com- puters in conjunction with dynamic RAM (DRAM) as they have different characteristics. Unlike DRAM chips, SRAMs do not need to be refreshed while in operation, thus providing fast access. As with many other types of memory chips, they require power to retain their information. See dynamic RAM. static route A data transmissions path that is fixed and stored in a table or other form of database in a network router or high-end switcher (the distinction between routers and switchers is not as great as it used to be). Static routing is often faster than dynamic routing, but is not suitable for all types of installa- tions. Static routing works well in small systems or those in which the routes are fixed and known, whereas dynamic routing is suitable for large, chang- ing, distributed networks. station A phone, computer, or other telecommuni- cations device selVice office, console, or workstation. station battery A battery used in early telephone switching stations which commonly provided 48V direct current (DC). station clockA centralized timing clock which provides a local reference for broadcast or other telecommu- Static Electricity Generator discharging rods conducting rods with brushes collecting forks revolving glass plates drive wheel Leyden jar This excellent example of a staticgeneratingmachine mountedon a base with Leyden jar condensers on eitherside is on exhibit in the American Radio Museum. discharging rods __ ___ ):======( revolving glass plates Leyden jar This schematic diagram shows the basic components of a static generator which functions in essen- tially the same way as the oneshown in thephotosabove. A Leydenjar ispositioned at each side, with the revolvingplates in the center. The discharge rods are shown across the top. 888 © 2003 by CRC Press LLC nications functions carried on at that station. Timing information may be actively transmitted from the sta- tion clock to other equipment. In broadcast stations in North America, the idiosyncrasies ofblack and white TV caused discrepancies in playback speeds ofdifferent media, even though they might use the same time-code basis. Thus, the playing time of a broadcast may be considered compensated when it has to be adjusted to match the station clock. In networks, internal clocks and station clocks are used to provide timing information. In very precise timing situations, such as in astro- nomical observatories, cesium-beam station clocks may be used for timing purposes. STE 1. See Section Terminating Equipment. 2. Sta- tion Terminal Equipment. 3. Spanning Tree Explorer. steady mark condition With multiple telegraph keys arranged in series, when not sending, an operator would close a switch to short the key contacts in or- der to leave the series unbroken. It puts the idle line into asteady mark condition. stealth Secretive or furtive action or application. In computing, stealth products or processes intended to be active without detection, such as a viewing portal or recording system that allows people or processes to be monitored without their knowledge. Account- ing, audit, or jobperformance applications are some- times run in stealth mode. System operators often run stealth processes to monitor regular or unauthorized activities on computer networks or individual ma- chines. Hackers use stealth measures to break into computer systems or to investigate processes or switching systems. stealth server In distributed networks using domain name systems, a stealth server is similar to a slave server in that it is an authoritative server, but differs in that it is not identified in the name server's regis- ter and thus would be visible to other servers only if explicitly known by a static identifier. See slave server. Stearns, Joseph B. (ca. 1830s-1895) An American inventor who designed and built Norumbega castle in 1886 near Penobscot Bay, Maine. He invented im- portant aspects of duplex telegraphy that were pat- ented in 1872 (U.S. #126,847 and #132,933). Stearns' system was initially used on the Franklin Telegraph Company lines and later on the Western Union lines. He sold the rights to duplex telegraphy to Western Union. Thomas Edison later extended the concept to create a quadruplex system in which two communi- cations could be sent in two directions at the same time. There are some briefreferences that a 1. Fisher may have introduced duplex telegraphy even earlier, but the author was unable to find any solid documen- tation to confirm this. Documents such as Stearns' Western Union member- ship cards and the Stearns patents of 1872 to 1874 (and reissued patents of 1880 to 1882) are in the West- ern Union Telegraph Company Collection, 1848 to 1963. See Frischen, Carl; Gintl, Julius; duplex telegraphy. Steinheil, Karl(Carl) August von (1801-1870) An astronomer and inventor (and associate of Gauss) who experimented with an Earth conductivity method to send wireless communications over distance in the 1830s. Steinheil was born in Alsace, but settled in Munich, Germany. With Gauss, he proposed the use of rail lines as a conduit for returning electrical sig- nals. Steinheil developed a magnetic recording tele- graph that marked high and low dots on a ribbon of paper (very similar in concept to Vail's code used on the Morse telegraph a few years later). In 1836, he contributed to the development of standards for mea- surement. In 1839, he pioneered electric clocks and reported some of his telegraphic discoveries in An- nals of Electricity, Magnetism, and Chemistry. Ten years later he was involved in the organization oftele- graphic communications in Austria. He is also known for inventing optical technologies. See conductivity method. See Sommering, Samuel Thomas. Steinmetz, Charles Proteus (1865-1923) A Ger- man-born American electrical engineer acknowl- edged for his genius in the investigations of lightning, alternating current phenomena, magnetism, and other discoveries which led to the development of safer power distribution systems and better motors, gen- erators, and electrical appliances. step boltAbolt or large rivet or smaller bolt or rivet supporting a rung, intended to assist aclimber in find- ing footing while climbing, as in a high-voltage line supporting tower. As towers age, the bolts tend to rust or even disappear altogether, causing risk to the climber, unless the bolts are maintained and replaced when needed. Tower maintenance workers are cau- tioned to place their gloved hands on the side sup- porting structures rather than on the step bolts, in case of a slip or fall. step-by-step switch An early electromechanical au- tomatic telephone switching system developed in 1920 and quickly favored by independents. It used rotating blades for setting switching connections. In competition with this, AT &T developed the first com- mercial panel switch in 1921. This type of switch was widely used until the mid-1970s, when crossbar switches superseded most panel switches and many step-by-step switches. Step-by-step switches must be modified to support touchtone dialing. See Callender switch, crossbar switch, Lorimer switch, panel switch. stepdown transformer A power transformer that provides voltage conversion from ahigher to alower level. This type of system is commonly seen on util- ity poles carrying primary power to secondary power users and individual drop points. See diagram. stepped index In a fiber cable, adjacent concentric layers with differing refractive indexes. The core has a slightly higher refractive index than the cladding, which causes the light to be reflected back into the core to continue along the waveguide. Stepped index is essentially an abrupt transition (though it need not be a large difference to be effective), in contrast to graded index fiber in which the refractive index de- creases gradually as the distance from the center in- creases. See graded index. 889 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Stepdown Transformers on Utility Poles Stepdown transformers are common components of utilitypoles carryingprimalypower between substa- tions (upper) and secondary power for residential/ small business subscribers (lower). Here the connec- tions are shown between the higher-voltage conduc- tors all the crossamls to the three transfomlers at- tachedwith brackets to the pole to the conducting lille for the secondmy power fed via connecting lines to the adjacent buildings. [Classic Concepts photo.} steradian (symb. - sr) Aderived SI unit ofsolid angle that is independent ofscale. The name is related to raidan, which is an SI unit for plan angle. Both may be expressed in meter units. There are about 12.5664 steradians in a sphere as derived from a conical shape radiating out from the center of the sphere with the area at the portion bounded by the cone at the surface of the sphere equal to the radius squared. The steradian is useful in expressing light measure- ments. In conjunction with watts, the steradian is a standard unit of luminous intensity. See candela, lu- minous intensity, spat. Stibitz Complex Number Calculator The first re- lay calculator, released in 1939, developed at Bell Laboratories. Stibitz, George R. (1904-1995) An American math- ematician and researcher at Bell Telephone Labora- tories who developed relay arithmetic devices in the mid-1930s. Stibitz began to study binary circuits and the various applications of binary systems. This led to Stibitz's subsequent development, in collaboration with Samuel B. Williams, of an electromagnetic re- lay calculator, the Complex Number Calculator, which could manipulate complex numbers. By 1940, this machine had become the Bell Labs Model I and was incorporated into the telephone network in such a way that it could be remotely accessed, setting an early precedent for future network systems. Stibitz thereafter served as a consultant to the U. S. Office 890 ofScientific Research and Development. Stibitz' con- tinued interest in calculating machines and comput- ers led to the awarding of a patent for a computing system that was a forerunner of modern digital com- puters, in February 1954 (U.S. #2,668,661). In 1997, the American Computer Museum launched an annual award to honor living pioneers of the com- puter and information age and named it in honor of George R. Stibitz. STL I. Standard Telegraph Level. 2. Studio-to-Trans- mitter Link. stocktickerA type ofearly stock reporting machine, somewhat resembling an anniversary clock with me- chanical parts within a glass globe on a round base. This machine used a paper tape and telegraphic line hookup to provide fast reporting ofstock activities with alphanumeric characters. In many ways, stock tickers led to asynchronous telecommunications. Stoke's shiftA loss ofenergy during an excited state of an electron where internal forces bring the excited electron to the first level singlet. In observations of fluorescence, the difference between the peak exci- tation wavelengths and the emission wavelengths. The concept of the Stoke's shift is important in a number of fields related to telecommunications, including spectroscopy. In fiber optics, it applies to shifts that occur in doped in-fiber amplification tech- nologies that help overcome signal loss through at- tenuation. See Stoke's theorem. Stoke's theoremAtheorem pertaining to vector cal- culus that describes a relationship between surface integrals over an open, spatially oriented three-dimen- sional surface and closed line integrals along the con- tour bounding the surface. It enables surface integrals to be mathematically reduced to line integrals and vice versa. This is useful for analyzing vector fields in electromagnetics. It is related to Green's theorem, which provides relationships between closed path line integrals and plane integrals for curves lying in a two- dimensional plane. Stoll, Clifford (1950- ) Author of A Cuckoo sEgg (1989), an account ofcomputer espionage by foreign infiltrators as experienced by Stoll, who was deter- mined to track down the source of a tiny, but puz- zling accounting error, and found much more. This account ofremote hacking was only the tip of the ice- berg in terms of what was subsequently learned about computer penetration into unauthorized systems, computer theft, and fraud and thus has become aclas- sic nonfiction techie thriller. In his second book Silicon Snake Oil, Stoll takes a step back and looks at the pros and cons of digital technologies and how they have affected our world. Stoner, Don (ca. 1932-1999) An American electron- ics experimenter and amateur radio enthusiast who, in 1957, suggested the amateur construction ofa re- lay satellite capable of two-way communications. This idea was in advance of its time, preceding the widespread use of electronic transistors and the con- struction of government two-way communications satellites, and inspired the development of the OS- CAR satellites. Stoner wrote about his ideas for © 2003 by CRC Press LLC amateur radio space research in QST in 1961. In 1971, along with Pierre Goral, Stoner formed Stoner-Goral Communications (SGC) to sell radio equipment, 70% ofwhich is not exported outside the u.s. Stoner retired in 1989 but continued to pursue the advancement ofamateur radio until his death. He was editor for a time of CQ magazine and founder and head, for a time, of the National Amateur Radio Association. His callsign was W6TNS. storage area network SAN. A somewhat catchall phrase for new systems for handling large amounts of data stored on avariety of types of media, accessed by avariety ofremote users on a network. The model ofa single hard drive and floppy drive on adedicated workstation is impractical for heterogenous, high- capacity storage; high-demand storage needs on evolving local area and distributed public networks. A SAN is a general effort to efficiently organize, ad- minister, and evolve storage solutions for heterog- enous network environments. This more general con- cept is distinct from network access storage (NAS), which implies the consolidation ofnetwork storage resources. SAN is a broader concept, encompassing many different types ofsolutions for handling stor- age devices and data-need dynamics. SAN is also more narrowly defined by commercial vendors as storage devices optimized for use on dis- tributed networks. See network-attached storage. storage cell, accumulator A secondary source of electricity, since it does not provide power immedi- ately, but rather is charged up and then used. Car bat- teries are typically lead-acid storage cells that derive their power from agenerator when the car is running, then store the power for later starting of the vehicle or operation of its electrical system when the motor is not running. See solar cell. store-and-forwardA technique for temporarily hold- ing infonnation until the conditions are right for trans- mitting the data to the receiver. This method is very common on data networks, where arouter, local net- work, or individual machine may be offline or down. The data may be held indefinitely and transmitted when conditions are right (the right time, when traf- fic is lower, when the recipient is online, etc.), or may be bounced back to the sender afteracertain interval or number of tries. It may even be abandoned, de- pending upon its nature and priority level. store-and-forward repeaters Transmission devices that store and forward information when conditions are favorable. In radio receiving and transmitting sta- tions, both Earth and satellite stations, the conditions for transmitting a received signal may not be opti- mal right away, due to weather, political unrest, high traffic levels, or the movement of a satellite out of transmissions range. The message is thus not sent until conditions improve or the satellite comes into a favorable position in orbit. Storey, G.J. Scientist who first used the term electron, in 1891, to specifically describe an electric charge. StorrerinsulatorA type of early utility pole insula- tor patented by L. W. Storrer in 1906, and first shipped by the Brookfield Glass Company in 1909. See in- sulator, utility pole. STP 1. shielded twisted pair. 2. See Signal Transfer Point. See Signaling System 7.3. Spanning Tree Pro- tocol. STPC 6800 An early Motorola MC6800-based com- puter kit from Southwest Technical Products Corpo- ration. It featured 2048 bytes ofstatic memory, a se- rial interface, case, and cover in the fall of 1975, and sold for $450 without a monitor or keyboard. See Altair 680, SPHERE System. strain insulator, linkstrain insulatorA historic util- ity pole insulator that French inventor C. Priestley submitted for apatent in 1910. The Ohio Brass com- pany acquired the rights and the patent was granted in 1912. It was in production, with variations, for about 30 years. This is also known as a hog orpork liver insulator due to the brown or tan coloring and the blobby dimpled saddle shape that allowed the conductive line to be fed through a channel connect- ing the dimples. The dimple channel configuration provided some protection in case the insulator broke, as it could still hold the cable. See saucer insulator, suspension insulator. strain relief boot Aprotective strengthening sheath that fits over cables in sections where there may be pressure or pulling strain against the cable. Strain re- lief boots are often fitted over the point ofcoupling between a cable and cable jack. See ST- connector. strand A single long thread of uninsulated wire. When two or more ofthese strands are combined or twisted around one another in the same bundle, it is called stranded wire. Wire is stranded for a number of reasons; it can make it more flexible and it may alter the electrical characteristics of the wire for some parti cular purpose. StrataCom A commercial supplier of ATM-related telephone networking products, particularly Frame Relay switching systems and network management control software based on open, standards-based in- terfaces for integrating with othervendors' products. stray light Light outside the effective wavelengths or wavelengths of observational interest. Undesired stray light may reach a viewing component or detec- tor from a number of sources, including external re- flected light, light scattered from imperfections in optical mechanisms, or flaws in grating corrugations. Interference gratings have been found to be much less susceptible to stray light effects than ruled gratings, especially when the grating corrugations are densely configured. Stream Control Transmission Protocol SCTP. A reliable network transport protocol designed to trans- port public switched telephone network (PSTN) sig- naling messages over Internet Protocol (IP) networks. SCTP was submitted as a Standards Track RFC by Stewart et al. in October 2000. SCTP operates over connectionless packet networks such as IP. It is modeled as a layer between the SCTP user application and aconnectionless packet network service in the context of an association between two serp endpoints. See RFC 2960. stream protocol See byte-stream protocol. 891 © 2003 by CRC Press LLC . Fiber Optics Illustrated Dictionary of both store-and- forward and realtime facsimile pro- tocols (ITU-T T.37, T.38). spoofing, network In network. (though it need not be a large difference to be effective), in contrast to graded index fiber in which the refractive index de- creases gradually as the distance from the center in- creases. See graded index. 889 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary Stepdown. software term for an unchanging or uneditable object in an application or document. Im- ages are often embedded as static objects in word pro- cessed documents, and can only be edited by locat- ing the source document, changing it in the original context, and updating the static