Electronics Glossary – S
Distributors of Commercial, Industrial, Medical, Automotive, and Hi-Rel Electronic Components
| Term | Definition |
|---|---|
| SA | Selective Access or Selective Availability |
| safetying | A term used to cover the use of product features designed to prevent the loosening of hardware, or other mating elements, under conditions of shock and vibration. Elements drilled for safety wiring would be an example of this type of feature. |
| Saturable Reactor | Describes the main element of a magnetic amplifier used to control electrical power such as for electrical resistance element heating of furnaces. |
| Saturated | The state of operation of a device or circuit in which there is no increase in output for an increase in input |
| saturation | The condition in which a further increase in one variable produces no further increase in the resultant effect. The condition occurring when a transistor is driven so hard that it becomes biased in the forward direction. In a switching application, under saturation conditions the charge stored in the base region prevents the transistor from turning off quickly. |
| Saturation | Exists when an increase in magnetizing force (H) does not cause a corresponding increase in the flux density (B) of the material. The cause of saturation is relative to the magnetic properties of the core. Each material can store only a given amount of magnetic flux density. Beyond this the permeability of the core is reduced dramatically causing inductance to fall. |
| Saturation Current | The DC bias current flowing through tile inductor which causes the inductance to drop by a specified amount form the initial zero DC bias inductance value. Common specified inductance drop percentages include 1-% and 20%. IT is useful to use the 10% inductance drop value for ferrite cores and 20% for powdered iron cores in energy storage applications. The cause of the inductance to drop due to the DC bias current is related to the magnetic properties of the core. The core, and some of the space around the core, can only store a given amount of magnetic ~ density. Beyond the maximum flux density point, the permeabilty of the core is reduced. Thus, the inductance is caused to drop. Core saturation does not apply to air-core inductors (Also see Incremental Current and Permeability) |
| Saturation Flux Density | The flux density value at which a given material saturates. |
| SAW | Surface acoustic wave. Often short for surface acoustic wave filter. |
| S-band | The frequency interval from 2 to 4 GHz. |
| SC connector | A duplex optical fiber connector. The standard connector for optical fiber per the 568 cabling standard. |
| Scalar | Of or pertaining to magnitude but not phase. |
| scale factor | One or more coefficients used to multiply or divide quantities in a problem in order to convert them to a given magnitude (eg plus one to minus one). |
| scanner | An electromechanical or electronic device, normally cyclic in nature with N number of steps – starting at a predetermined point and returning to that same point. The word scanner is sometimes used interchangeably with multiplexer. |
| SCD | Specification Control Drawing – Drawing that defines configuration and material parameters. Issued and controlled by the specifications group, SCDs are frequently used in conjunction with RT Specifications for Thermofit products. |
| schematic | A “scheme” for presenting information. Thus, a circuit schematic – in diagrammatic form – indicates the components, wiring, and connections of the circuit. |
| Schmitt trigger | A bistable trigger circuit that converts an input signal into a square-wave output signal by switching action, triggered at a predetermined point in each positive and negative swing of the input signal. |
| Schottky | A metal-semiconductor junction that has a nonlinear voltage versus current characteristic. |
| Schottky TTL | A type of TTL notable for faster operating speeds than standard TTL. |
| Scoop-proof | A feature that prevents the damage of contacts during misaligned mating. |
| scratch pad memory | A computer information store that interfaces directly with the central processor. It is optimized for speed and has a limited capacity. Its purpose is to supply the central processor with the data for the immediate computation without the delays that would be encountered by interfacing with the main memory. |
| screw-machine contact | A contact which is machined from solid bar stock. |
| scribing | The scratching of a brittle substrate, such as alumina or silicon, to ensure cleavage along the scratch line. Wafers are scribed and then broken to produce integrated circuit chips. |
| SD | Secure Digital (Flash memory) |
| SDH | synchronous digital hierarchy |
| SDLC | An IBM data-communication protocol. |
| SDSL | Symmetric Digital Subscriber Line. |
| SE | Shielding Effectiveness – The reduction in field strength resulting from interposing a metallic barrier between a source and receptor of electromagnetic energy. |
| Sealant | Soft, tacky, pliable material that seals where mechanical strength is not required. |
| Sealed | Environmentally protected by the thermoplastic inserts or core of encapsulant/ adhesive that has melted down around the substrate. |
| sealing plug | A plug used to fill and seal an unoccupied contact cavity in a housing or insert. Its role is especially vital in environmental connectors. |
| Secant Modulus | A measure of material stiffness; stiffer material has a higher secant modulus. More specifically, the secant modulus is the ratio of stress (nominal) to corresponding strain at any specified point on the stress-strain curve.It is expressed in force per unit area (usually kilograms per square centimeters or pounds per square inch), and reported together with the specified stress or strain. |
| Secondary Circuit | Output side of an isolated DC-DC converter. Also see Primary Circuit. |
| Secondary Winding | The winding in a transformer that supplies the load with electrical energy which has been converted from the induced magnetic energy in the core. |
| sector | The smallest addressable unit of information (set of bits) in a drum or disk memory. |
| selective plating | A process of plating only a selected portion of a contact, usually the mating surface. Two methods can be used: 1) Nickel plating the entire contact, then gold plating the selected area. 2) Nickel plating and then gold flash over the entire contact, and finally a selective heavy gold plating in the desired contact area. |
| Self Resonant Frequency | SRF – The frequency at which an inductor’s distributed capacitance resonates with the inductance. The inductive reactance and the capacitive reactance are equal. The inductor acts as a pure resistance. The Q of an inductor is equal to zero at the SRF. |
| self-aligning | Mating parts designed so that they can engage only in the proper relative position. |
| self-extinguishing | A loosely-used term describing a material’s ability to cease burning when the source of flame is removed. See also flame resistance. |
| Self-Inductance | Another way of saying inductance. |
| Self-Powered Hub | Class of devices that derive power from its own source. Examples include monitors and self-powered USB hubs. |
| SEM | Scanning electron microscope, in which a beam of electrons systematically sweeps over the specimen. The intensity of the secondary electrons generated at the point of impact is measured, and the resulting signal is fed to a CRT display, which is scanned in synchronism with the scanning of the specimen. |
| semiconductor | Materials whose electrical conductivity is between that for good conductors and that for good insulators. Their conductivity may be changed by heat, light, electric field, or magnetic field. Examples include: germanium, lead sulfide, lead telluride, selenium, silicon, and silicon carbide. A semiconductor device, such as a transistor, is frequently referred to simply as a “semiconductor.” |
| semiconductor device | A solid state electronic device in which conduction takes place within a semiconductor. By careful processing, certain semiconductors (primarily germanium and silicon) can be used in these electronic devices which perform many or all of the functions of thermionic tubes (vacuum tubes). In many applications, their small size, long life, and low power requirements make them superior to tubes. |
| semi-rigid | A cable containing a flexible inner core and a relatively inflexible sheathing. |
| Sendust | A 9% silicon, 6% aluminum, and 85% iron alloy in particulate form. The particles are coated with a dielectric film, compacted, and cured to form magnetic parts such as inductor cores. |
| Sense Line | Output line used in a remote sensing connection to route the output voltage (at the load) back to the control feedback loop. Also see Remote Sensing. |
| sensitivity | Measure of the ability of a device or circuit to react to a change in some input. Sensitivity can also be the minimum or required level of an input necessary to obtain rated output, as in an amplifier. For a fiber-optic receiver, the minimum optical power required to achieve a specified level of performance, such as a BER. |
| sensitivity switch | A switch having a snapaction, microgap mechanism which is operated directly by a defined force through a defined travel. |
| separable part | A replaceable part, designed to be removed without risk of destroying or damaging adjacent elements. Crimping, chemical bonding, etc preclude assurance of safe removal, and parts so attached would not be deemed separable. Protective coatings, solder, etc normally do not preclude safe removal, and parts so treated – barring other factors – may still be classified as separable. |
| separating force | Force required to either engage or separate contacts – both in and out of the connector housing or insert. Values are generally established for maximum and minimum forces. Performance acceptance level vary per specification or customer requirements. Sometimes the forces are not only measured initially, but also after specified number of engagements and separations. |
| sequencer | A mechanical or electronic device used to initiate and control the predetermined sequence of a series of events. |
| sequencing | The process of performing a series of operations in a predetermined order. |
| serial memory | A memory whose information media is continuous. Data is identified in its content or form. Data may be obtained only by performing a serial search through the contents of the memory. A magnetic tape is serial. |
| serial operation | The flow of information through a device in time sequence – using only one digit, word, line, or channel at a time. For example, all bits of an 8-bit word are transmitted one bit at a time over a single line. Much slower than parallel operation. |
| serial transfer | Data transfer in which elements of information are transferred sequentially. |
| serial transmission | Transmitting character bits in line sequence. Generally used in telegraphic-type operation. |
| series | Connecting components in a circuit end-to-end to provide a single path for current flow. |
| Series Operation | Master-slave configuration in which two or more isolated converters are connected to obtain a hgher output voltage level (converter inputs connected in parallel) or wider input voltage range (converter inputs connected in series) than that obtainable from one module. Also see Master-Slave Operation. |
| Series Regulator | Linear regultor (internal or external to the converter)placed in a series with the load to ahcieve a constant voltage across the load. This is the most popular method of linear regulation. Also see Linear Regulation, Post Regulation and Shunt Regulator. |
| Series Resistance | The real part of the complex impedance of a semiconductor device. The resistance of the semiconductor package, die attach and bond wire are typically included in series resistance. |
| Series-Shunt | The circuit configuration including two components, the first in series with the transmission line and the second in shunt with the transmission line. |
| serrations | The small grooves or indentations within a terminal wire barrel. The serrations increase the tensile strength and improve the electrical conductivity of the crimped termination. |
| Service Life | Period of time during which the product is expected to perform satisfactorily. |
| Service Loop | The extra cable required at a breakout to facilitate maintenance and servicing. |
| Service Rating | The maximum voltage or current that a termination is designed to carry continuously. |
| Set Up Transformer | When the secondary is at a higher voltage than |
| Settling Time | The time required for the device to attain 90 percent of the detected RF output referenced to the 10 percent level. |
| S-HDSL | Single pair transmission using HDSL technology, normally 2B1Q. |
| sheath | The outer covering or jacket over the insulated conductors to provide mechanical protection for the conductors. Also known as the external conducting surface of a shielded transmission line. |
| Shelf Life | Generally, the length of time a product or material may be stored without deterioration. Specifically, the length of time during which shrink tubing will retain its expanded ID and return to its recovered ID. Usually not a concern—except for some “amnesic†materials. See Amnesia. |
| Shell | The outside case, usually metallic, into which the insert (body) and contacts are assembled. Shells of mating connector halves usually provide for proper alignment and polarization as well as for protection of projecting contacts. |
| shf | See superhigh frequency. |
| Shield | A conducting layer placed around an insulated conductor or cable to limit the penetration, or escape, of electric or electromagnetic fields, thereby preventing electromagnetic interference. The shield may be formed of metallic braid, metal tape, metal-backed foil, metal tube, or conductive polymer. Usually grounded, the shielding is carried through the connector shell, or through a special internal shell in the case of individual coaxial contacts. |
| Shielded Inductor | An inductor designed for its core to contain a majority of its magnetic field. Some inductor designs are self shielding. Examples of these are magnetic core shapes which include toroids, pot cores and B-Cores. Magnetic core shapes such as slug cores and bobbins require the application of a magnetic sleeve or similar method to yield a shielded inductor. It should be noted that magnetic shielding is a matter of degree. A certain percentage of the magnetic field will escape the core material. This is even applicable to toroidal cores as lower core permeabilities will have higher fringing field than will high permeability toroidal cores (Also see Closed Magnetic Path.) |
| shielded keyboard | A keyboard assembly that has been designed to withstand severe EMI environments. Such shielding can also prevent noise from the keyboard from affecting nearby equipment. |
| shielded room | A room, used for EMI testing, having highly conductive walls that isolate the interior from the exterior to contain energy within the room and to prevent outside energy from entering the room. |
| shielding | (1) A conducting envelope, composed of metal strands, that encloses a wire, group of wires, or cable, so constructed that substantially every point on the surface of the underlying insulation is at ground potential or at some predetermined potential with respect to ground. (2) An isolation barrier placed around a circuit component to prevent interaction of its electric and/or magnetic fields with those of nearby elements. Shielding protects a circuit against crosstalk. |
| shielding effectiveness | A measure of the performance of a shield, typically expressed in decibels as (1) the ratio of energy incident on the shield to that emerging on the other side or (2) the ratio of energy emitted from an unshielded sample to the energy emitted by the same sample when it is shielded. |
| shift | To move information serially right or left in a register(s). Information shifted out of a register may be lost, or it may be re-entered at the other end of the register. |
| shift register | A shift register is an electronic device which can contain several bits of information. Shift registers are normally used to collect variable input data and send this data out in a predetermined pattern. |
| shock | (1) An abrupt impact applied to a stationary object. Usually expressed in gravities (g). (2)An abrupt and nonperiodic change in position, characterized by suddenness, and by development of substantial internal forces. |
| Shore | A scale for comparing hardness. Higher Shore values represent harder materials. The hardness of a polymer, for example, is usually represented as Shore A or Shore D, with D being harder. |
| Short Circuit Protection | Maximum steady-state current level at which the power switch output is regulated in response to an overcurrent fault. |
| Shot noise | Noise caused by random current fluctuations arising from the discrete nature of electrons. |
| Shrink Ratio | An expression of how much the inside diameter of shrink tubing will reduce in size when recovered. The inverse of the expansion ratio. See also Expansion Ratio. |
| Shunt | In parallel with; connector used to common two circuits. |
| Shunt Regulator | Linear regulator (internal or external to the converter) placed in parallel with the load to achieve a constant voltage across the load. Also see Linear Regulation, Post Regulation and Series Regulator. |
| SHV | Standard High Voltage – A quick connect/disconnect connector series employing bayonet lock coupling and designed to operate safely up to 5000 volts ac. It is the industry standard connector, specified by the National Bureau of Standards (NBS) for high voltage use by the Atomic Energy Commission (AEC). |
| Sideband Suppression | In a mixer or modulator, the degree to which undesired sidebands are reduced in amplitude. |
| sign bit | Computers generally indicate whether a number is positive or negative by a sign bit, which is usually located adjacent to the most significant numerical digit. Usually zero (0) is used for positive ( ) and one (1) for negative (-). |
| Signal Cable | A cable designed to carry current of less than 12 amperes per conductor. |
| Signal Frequency | In a mixer or detector, this is the desired RF or microwave frequency containing information (modulation). This is the frequency that is to be converted to a different (normally lower) frequency. |
| Signal Rise Time | The time for a signal to switch from low to high, usually measured between 10% and 90% of the maximum amplitude. |
| signal-to-noise ratio | SNR – The ratio of signal strength to noise level in an electronic system. |
| significant digit | A digit that contributes to the preciseness of a number. The number of significant digits is counted beginning with the digit contributing the most value, called the most significant digit, and ending with the one contributing the least value, called the least significant digit. |
| silicon | The semiconductor material most widely used for transistors, diodes, and monolithic integrated circuits. A brittle, gray, light metal. |
| silicon dioxide | The result of oxidizing silicon quartz. Selectively etched silicon dioxide permits the selective doping that generates components in monolithic integrated circuits. |
| silicon nitride | A silicon compound that is deposited on the surface of silicon monolithic integrated circuits to improve their stability. The nitride is relatively impervious to some ions that penetrate silicon dioxide. Best stability is obtained by a combination of silicon nitride and silicon dioxide. Charge storage at the interface of the nitride and dioxide layers has resulted in memory devices with extremely long retention times. |
| silicon oxide | A generic term referring to an unspecified mixture of silicon monoxide and silicon dioxide, such as may be deposited on a silicon integrated circuit as an insulator between runs in multilevel metallization. |
| silicon-controlled rectifier | SCR – A semiconductor device capable of only two stable states. When “off,” it blocks the flow of electricity in either direction. A small triggering voltage to its gate turns it “on,” and allows the flow of electricity in the forward direction only. When “on,” the SCR acts just like a conventional rectifier. To turn it “off,” voltage to the anode must be removed, or reduced to a potential less than that being applied to the cathode. |
| silicon-controlled switch | SCS – A semiconductor device with leads to all four regions. Can be integrated with transistors in monolithic integrated circuits. Useful as a small SCR or complementary SCR. |
| silo | A housing construction feature which increases the electrical current creepage path for high voltage ratings. May also provide polarization for mating connectors. |
| Simple Network Management Protocol | SNMP – A network management standard initially established to allow multi-vendor networking devices to be managed more easily with common management tools. |
| Simple Winding | A winding for a toroidal core which results in 78% of the cores inside diameter remaining. Often times this will produce a single layer winding. |
| simplex | A circuit which allows telecommunications in only one direction at a time; a one-way path for telegraph-type signals. |
| Simplex cable | A term sometimes used for a single-fiber cable. |
| Simplex transmission | Transmission in one direction only. |
| sine wave | A wave which can be expressed as the sine of a linear function of time, space, or both. A waveform (often viewed on an oscilloscope) of a pure alternating current or voltage. |
| Single Ended Mixer | The simplest form of mixer, which consists of a single nonlinear impedance connected across an unbalanced transmission line, to which RF and LO signals are applied and from which the IF signal is obtained. |
| Single Layer Winding | A winding for a toroidal core which will result in the full utilization of the inside circumference of the core without overlapping of turns. The thickness of the wire and tightness of the winding will affect results. |
| single mode | A fiber that allows only one path for the light to take due to the fiber’s very small diameter – less than 10 microns. |
| Singlemode | A type of optical fiber in which the light travels in a single path. Utilizes lasers as a light source. |
| Single-mode fiber | An optical fiber that supports only one mode of light propa-gation above the cutoff wavelength. |
| single-pole | A contact arrangement wherein all contacts – in one position or another – connect to one common contact. |
| Sintered Iron | Powdered iron that has been pressed and sintered into a structural form. This type of material occasionally is used in a magnetic application, but they normally exhibit excessive core losses. |
| Six-Sided Shielding | Converter packaging technique in which the unit is placed into a metal case. Theis metal shielding minimized any noise radiation from the converter components. A continous shielded case has the base (or header) welded on, further reducing potential noise leakage. |
| Skew | Any out-of-squareness of the cut end of a piece of tubing after shrinking. |
| Skewing Of The Loop | When an air gap is added to a magnetic path, the hysteresis loop is made to lean over (permeability is reduced). It is said to be skewed or sheared. |
| Skin Effect | Skin effect is the tendency for alternating current to flow near the surface of the conductor in lieu of flowing in a manner as to utilzie the entire cross-sectional area of tile conductor. Ths phenomenon causes the resistance of the conductor to increase. The magnetic field associated with the current in teh conductor causes eddy currents near the center of the conductor which opposes the flow of the main current flow near the center of the conductor. The main current flow is forced further to the surface as the frequency of the alternating current increasing (Also see Litz Wire.) |
| sleeve | The insulated, or metallic, covering over the barrel of the terminal. |
| slotted tongue | A terminal that has a slot rather than a hole in the tongue, so that the terminal can be engaged and disengaged from a stud without completely removing the nut. |
| Slug Core | A core shaped like a rod, with the winding(s) placed around the diameter. |
| SMA connector | A radio-frequency connector covered by Military Specification. It has an impedance of 50 ohms and an operating frequency range to 12.4 GHz. |
| Small Signal | The magnitude of an AC signal which, when its amplitude is halved or doubled, the characteristic under measurement does not change. |
| Small Signal Analysis | The consideration of the performance of a circuit or device under small signal conditions |
| small-scale integration | SSI – A single circuit function implemented in monolithic silicon. In complexity, a circuit of less than 10 gates. |
| SMD | Surface Mount Device |
| Smith Chart | A mapping of the complex impedance plane onto a polar plot. A Smith chart consists of circles of constant resistance that intersect at Z = Â and arcs of constant reactance that also intersect at Z = Â. The horizontal diameter of the Smith chart represents pure resistances from a short (0 W) at one end to an open (Â W) at the other end. The Smith chart was developed by Philip H. Smith in the late 1930’s. |
| SMO | Special Manufacturing Order – An order to evaluate manufacturing and production capability for a new or changed design for a customer and to provide development samples of potential products for customers. SMO products are separate and distinct from standard products. New, potential products are usually run as SMO products for a minimum of three times before being considered for manufacture as a standard product. |
| SMR | Specialized mobile radio. A communications service at 800 MHz and 900 MHz used to provide dispatch messaging and cellular communications. |
| SMS | Short Message System |
| Snap Time | The time required for a varactor or step recovery diode to change from the conducting to non-conducting state after reverse bias is applied, excluding the time required for charge to be conducted from the junction. It is normally measured from the 90 percent to 10 percent reverse current states. Also called transition time |
| SNR | Signal-to-noise ratio – The ratio of signal strength to noise level in an electronic system. |
| socket contact | A female contact designed to mate with a male contact or pin. It is normally connected to the “hot” side of the circuit because the housings that accept sockets usually fully surround, insulate, and protect the contact. |
| Soft Magnetic Material | A ferromagnetic material that is easily magnetized and demagnetized. |
| Soft Start | Converter input circuit that limits the inrush of current at turn on. |
| software | Computer programs. |
| SOG | Speed over Ground. (The actual speed the GPS unit is moving over the ground) |
| SOHO | small office/home office |
| Solder | An alloy that melts at relatively low temperatures and is used to join metals with higher melt points. |
| solder | An alloy that can be melted at a fairly low temperature, for use in joining metals having much higher melting points. An alloy of tin and lead in approximately equal proportions is the solder most often used for making permanent joints in circuits. |
| Solder Contact | A contact or terminal having a cup, hollow cylinder, eyelet, or hook to accept a wire for a conventional soldered termination. |
| Solder Cup | A tubular end of a terminal into which a wire conductor is inserted prior to being soldered. |
| Solderability | The property of a metal surface that allows it to be readily wetted by molten solder. See also Wetting. |
| solder-eyelet | A solder-type terminal, having a hole at its end through which a wire can be inserted prior to being soldered. See also eyelet. |
| Soldering | A process of joining metallic surfaces with solder without melting the base metal. |
| solderless | Without the use of solder. |
| SolderSleeve Device | A device of flux-coated solder preform encapsulated in a heat-recoverable plastic sleeve. Upon the application of heat, the flux and solder will melt and flow as the sleeve recovers, forcing the solder around and onto the metallic parts being joined, thus forming an electrically insulated and strain-relieved joint. |
| solenoid | An electrical conductor wound as a coil (helix) with a small pitch. When activated with an electrical current, it draws a movable core into the coil. |
| Solid Conductor | A conductor composed of one single strand. |
| Solid State | In electronics, having or pertaining to circuits that contain semiconductors. Note: In electro-optics, used to refer to lasers and related devices made of solid crystalline or amorphous materials other than semiconductors. |
| Soliton | An optical pulse that does not disperse over distance. |
| Solvent Resistance | The ability of a material to retain physical and electrical properties after being immersed in specific solvents. |
| Solvent Resistance Test | A test described in Raychem’s PS300 publication to test the durability of the markings on PolySwitch devices when exposed to various solvents. |
| Solvent Resistance Test | A test described in Raychem’s PS300 publication to test the durability of the markings on PolySwitch devices when exposed to various solvents. |
| SOM | start of message |
| SONET | Synchronous Optical Network- A recently emerging networking standard that utilizes fiber optics to create backbone networks, capable of transmitting at extremely high speeds and accommodating gigabit-level bandwidth. |
| sophisticated | Complex and intricate utilization of advanced art; requiring specific skills to operate. |
| Sorted | Binned refers to resistance-matched devices, which are supplied such that all parts in one particular package (or reel) are within 0.5 ohms of each other (1.0 ohms for TR250-080T devices). Individual matched packages are supplied from the full resistance range of the specified device. The benefit is that resistance-matched devices reduce the tip-ring resistance differential, reducing the possibility of line imbalance. Sorted devices are those that are supplied with resistance values that are within specified segments of the device’s full range of resistance, giving greater design flexibility. |
| Source | (1) The terminal at one end of the channel of a field effect transistor by which electron or hole current enters the channel. This terminal corresponds to the emitter in a bipolar transistor. (2) Power bus that drives the DC-DC converter. Also see Bus. (3) The light emitter, either an LED or laser diode, in a fiber-optic link. Spectral width A measure of the extent of a spectrum. For a source, the width of wavelengths contained in the output at one half of the wavelength of peak power. Typical spectral widths are 20 to 60 nm for an LED and 2 to 5 nm for a laser diode. |
| spade | A terminal with a slotted tongue that has nearly square sides. |
| Spanning Tree | An algorithm, the original version of which was invented by Digital Equipment Corporation used to prevent bridging loops by creating a spanning tree. The algorithm is now documented in the IEEE 802.1d specification, although the Digital algorithm and the IEEE 802.1d algorithm are not the same, nor are they compatible. |
| Spare Inputs | Extra inputs or unused inputs |
| Sparkover | A disruptive discharge between electrodes of a measuring gap |
| SPC | Silver-plated copper. |
| SPC | Statistical Process Control – The use of statistical techniques such as control charts to analyze a process or its output so as to take appropriate actions to achieve and maintain a state of control and to improve the capability of the process. |
| spdt | single-pole, double-throw – A three-contact switching arrangement which connects a circuit to either one of two alternate connections (called Form C). |
| specific gravity | The density (mass per unit volume) of any material divided by that of water at a standard temperature. |
| Specific Inductive Capacity | (also K) The ratio of the capacitance between two electrodes with a solid, liquid, or gaseous dielectric, to the capacitance with air between the electrodes. Also called permittivity and dielectric constant.Generally low values are desirable for insulation. |
| Specification Control Drawing | SCD – Drawing that defines configuration and material parameters. Issued and controlled by the specifications group, SCDs are frequently used in conjunction with RT Specifications for Thermofit products. |
| specs | Abbreviation for specifications. A control document which establishes the parameters that a given product, or type of product, must meet. Firms use specifications for control in manufacture, Government agencies use them for control in procurement, and other bodies – such as UL – use them as a basis for approval. |
| spectral dispersion | Due to a band of wavelengths (colors) put out by a light source. Each separate color has a different speed through the fiber causing different colors to arrive at different times, making the pulse appear longer than originally generated. |
| SPICE | Semiconductor Parameter In Circuit Emulator – a software package that emulates circuit performance utilizing time domain analysis |
| Splice | A joint connecting conductors with good mechanical strength and conductivity; a terminal that permanently joins two or more wires. |
| Splitter | A component that divides the power from a signal into two or more parts |
| spring properties | The relationship between applied force and resulting deflection which characterize the potential loading conditions of a given system (ie, usually refers to the elastic properties of a system). |
| spring-finger action | A type of spring design – as used in a printed circuit connector or a socket contact – which permits easy, stress-free spring action to provide contact pressure and/or retention. |
| SPS | Standard Positioning Service (see also PPS) |
| spst | single-pole, single-throw – A two contact switching arrangement which either opens or closes one circuit. This circuit may be normally open (NO, called Form A), or normally closed (NC, called Form B). |
| Spurious | Undesired signals present at the output of a device under test that are neither harmonics nor intermodulation products, sometimes expressed as a percentage of or decibels below the carrier. |
| sputtering | A thin film technique in which the film material is ejected from the surface by the action of ion bombardment. |
| Square Wave | An excitation that consists of an abrupt on/off cycling of the voltage. This typically goes in both the positive and negative direction. A positive-only square wave would be typical of pulse excitation. |
| Square-Law Detection | Detection of an RF/microwave signal where the magnitude of the detected video output voltage is proportional to the square of the RF input voltage |
| Square-Law Detector | A detector circuit or device whose video output voltage is proportional to the square of the RF input voltage |
| Squareness Ratio | The ratio of residual flux density to the maximum (saturation) flux density. |
| SRF | Self Resonant Frequency – The frequency at which tile inductor;s distributed capacitance resonates with the inductance. It is at this frequency that the inductance is equal to the capacitance and they cancel each other. The inductor will act purely resistive with a high impedance at the SRF point. The distributed capacitance is caused by the turns of ~re layered on top of each other and around the core. This capacitance is in parallel to the inductance. At frequencies above the SRF, the capacitive reactance of the parallel combination will become the dominant component. Also, tile Q of the inductor is equal to zero at the SRF point since the inductive reactance is zero. The SRF is specified in Mhz and is listed as a minimum value on product data sheets (Also see Distributed Capacitance) |
| SSI | Small Scale Integration – A single circuit function implemented in monolithic silicon. In complexity, a circuit of less than 10 gates. |
| ST connector | A bayonet style optical fiber connector.An alternate style per the 568 standard. |
| stamped and formed contact | A contact which is stamped from a flat sheet of metal and then formed through a progressive die. |
| Standby Current | Current drawn by a converter when it has no load and has been shut down by a logical inhibit signal. |
| Standing Wave Ratio | The ratio of the maximum magnitude of a standing wave to the minimum magnitude. SWR is indicative of the degree to which there is a mismatch between the characteristic impedance of the transmission medium and its load. A standing wave ratio of 1:1 indicates a perfect match (all the power incident on the load is absorbed by the load), while SWR = Â indicates a complete mismatch (all the power incident on the load is reflected by the load). |
| Standing Waves | The sum along a transmission medium of incident and reflected waves, characterized by maxima and minima along the medium. |
| standing-wave | Distribution of current and voltage on a transmission line, resulting from two sets of waves traveling in opposite directions. |
| standing-wave ratio | SWR – The ratio between maximum and minimum current, or voltage, along a line. It is a measure of the mismatch between the load and the line, and is equal to 1 when the line impedance is perfectly matched to the load. (In that case the maximum and minimum are the same, as current and voltage do not vary along the line.) The perfect match would be referred to as a 1 to 1 ratio. Vswr is voltage standing wave ratio. |
| Star coupler | A fiber-optic coupler in which power at any input port is distributed to all output ports. |
| Star network | A network in which all terminals are connected through a single point, such as a star coupler. |
| start of message | SOM – Usually a unique character in a data stream that indicates the beginning of a block of information data. See also start sentinel. |
| start sentinel | The binary coded character used to determine the start of a message on a magnetic stripe credit card. |
| State Machine | A sequential network is used to control a digital system that carries out a step by step procedure or algorithm |
| Statistical Process Control | SPC – The use of statistical techniques such as control charts to analyze a process or its output so as to take appropriate actions to achieve and maintain a state of control and to improve the capability of the process. |
| statistical quality control | The application of statistical methods to the identification, prediction, measure, and correction of problems in quality control. |
| stator | The portion of a rotating machine that contains the stationary parts of the magnetic circuit and their associated windings. |
| Steady state | Equilibrium mode distribution. |
| Step Change | Sudden change in a converter parameter. Typically used in referring to changes in output load or input line during converter testing. |
| Step Down Transformer | When the secondary has a lower voltage than the primary. |
| step index | A fiber construction where the core is one distinct index of refraction and the cladding a lower one causing the light to travel down a fiber by reflecting off the corecladding interface. |
| Step-index fiber | An optical fiber, either multimode or single mode, in which the core refractive index is uniform throughout so that a sharp step in refractive index occurs at the core-to-cladding interface. It usually refers to a multimode fiber. |
| stop sentinel | The binary coded character used to determine the end of a message on a magnetic stripe credit card. |
| storage | system memory |
| Storage Temperature Range | Range of ambient temperatures over which a component can be stored safely (Also see Operating Temperature Range) |
| STP | Shielded Twisted Pair.2-Pair 150 ohm shielded cable. |
| Strain Relief | The technique for or act of removing or lessening the strain or stress on a joint, splice, or termination. SolderSleeve devices provide strain relief. |
| strain relief clamp | A device used to give mechanical support for the contacts from the weight of a wire bundle or cable. May be referred to as cable clamp. |
| Strand | A single unit of a conductor. |
| Stranded Conductor | A conductor composed of more than one single strand. The strands in stranded conductors are usually twisted or braided together. |
| Strength member | That part of a fiber-optic cable composed of Kevlar aramid yarn, steel strands, or fiberglass filaments that increase the tensile strength of the cable. |
| Strip | (1) To remove insulation from a wire or cable. (2) “Strip” terminals (or contacts) are produced in continuous lengths, and placed on reels, for application in automatic or semi-automatic machines. |
| Stripe | A continuous longitudinal or spiral color strip applied on the surface of a wire, cable, or tubing for identification. |
| Stripline | A multi-layer transmission line that consists of two ground planes, separated by two layers of dielectric material that sandwich between them a thin center conductor that has a rectangular cross section. The impedance of stripline is determined by the thickness and dielectric constant of the dielectric layers and the width of the center conductor. |
| stud | A metal rod or pin (bolt) projecting from a piece, for the attachment and/or support of a second piece. The projecting end of the stud most commonly has screw threads, and the second piece is secured with a nut. |
| stud hole | The hole or slot in the tongue of a terminal, made to accommodate a screw, bolt, or stud of a given size. |
| styrene-butadiene | Copolymer synthetic rubber characterized by good electrical properties and moisture resistance. Ozone resistance, physical properties, and chemical resistance are generally improved by blending with other materials. |
| subassembly | Two or more parts which form a portion of an assembly (or a unit replaceable as a whole), but having a part or parts which are individually replaceable. |
| subminiaturization | The packaging of miniaturized parts, using unusual assembly techniques to increase volumetric efficiency. |
| substrate | The physical material on, or within, which the elements of an integrated circuit are fabricated. Ceramic, plastic, and glass substrates satisfy the primary functions of mechanical support and insulation, but semiconductor and ferrite substrates may also provide useful electrical functions. See also wafer. |
| subsystem | An interconnection combination of a set of related circuits, which form a logical subdivision of an equipment or operational system. |
| SUPER CHAMP | The AMP trademark for a stamped hand tool designed to crimp 22-10 insulated terminals. This tool also cuts and strips wire and shears 4/40 through 10/32 bolts. |
| Super Compact | A software package that analyzes and optimizes RF/microwave circuits using frequency domain analysis. |
| superhigh frequency | shf – A Federal Communications Commission designation for the band from 3,000 to 30,000 MHz in the radio spectrum. |
| Supply Current | Rated output current of a given device. Power switch devices have been designed to support a continuous load (supply) current of 0.6A at ambient temperature. |
| Supply Voltage | Voltage level of the power switch input. Raychem power switch devices have been designed to operate using supply voltage levels from 3.0V to 5.5V. |
| Surface Area | The effective surface area of a typical wound core available to dissipate heat. |
| Surface Resistance | The ratio of the direct current applied to an insulation system to the current that passes across the surface of the system. |
| surface-mount device | An electronic component, ranging from discrete passive components to VLSI chips, attached to the surface of a printed circuit board, either directly or through a surface-mount connector, rather than by means of holes in the board. |
| surge | A transient variation in the current and/or potential at a point in the circuit. |
| SV | Space Vehicle |
| swedging | Another term for crimping. |
| Swing | A term used to describe how inductance responds to changes in current, ie a 2:1 swing corresponds to an inductor which exhibits two times more inductance at very low current than it does at its maximum rated current. This would also correspond to the core operating at 50% of initial permeability (50% saturation). |
| Swinging Inductors | A special type of inductor that exhibits high inductance at low MMF and moderate inductance at high MMF. There are two popular techniques for accomplishing this: placing a common winding on a high permeability core and a low permeability core, and placing a staggered gap into a high permeability core. |
| Switch | (1) A mechanical or electronic device used to make or break an electrical circuit. (2) An N-port device that directs energy from one port to another or interrupts the flow of energy. A switch can use mechanical, electromechanical or electronic switching elements. (3) A type of network hub. Provides higher bandwidth than shared hubs. |
| Switch Mode Power Supply | A power conversion technique that involves breaking the input power into pulses at a high frequency by switching it on and off and re-combining these pulses at the output stage. Using this technique, an unregulated input voltage can be converted to one or more regulated output voltages at relatively high efficiencies. |
| Switched Virtual Circuit | SVC – A virtual link, with variable end-points, established through an ATM network. With an SVC, the user defines the end-points when the call is initiated that are subsequently terminated at the end of the call. With a Permanent Virtual Circuit(PVC), the end-points are predefined by the network manager. A single virtual path may support multiple. |
| Switching Frequency | The rate at which the DC input to a switching regulator is switched on and off. |
| Switching Regulator | A circuit that is designed to regulate the output voltage, from a given input voltage, by using a closed control loop design. The most common switching regulator types involve a magnetic component, such as an inductor or transformer, that is used to store and transfer energy to the output by having the current switched on and off (Also see Boost Regulator and Buck Regulator) |
| Switching Time | The time required for the output of a switch to attain 90 percent of its steady-state level referenced to the 50 percent level of the command signal. |
| SWR | Standing Wave Ratio – The ratio between maximum and minimum current, or voltage, along a line. It is a measure of the mismatch between the load and the line, and is equal to 1 when the line impedance is perfectly matched to the load. (In that case the maximum and minimum are the same, as current and voltage do not vary along the line.) The perfect match would be referred to as a 1 to 1 ratio. Vswr is voltage standing wave ratio. |
| Symmetrical Transmission | Transmission in which a channel sends and receives data with the same signaling rate. |
| synchronize | Make sure that the level or pulse is presented to the system, or subsystem, at the correct time. |
| synchronizer | A computer storage device used to compensate for difference in rate of flow of information, or time of occurrence of events, when transmitting information from one device to another. |
| synchronous | A device or system in which all events occur in a predetermined timed sequence. Usually all parts operate to a common clock. See also asynchronous. |
| synchronous generator | An alternator (ac generator); a synchronous alternating-current device which transforms mechanical power into electrical energy. |
| synchronous transmission | Transmission in which the data characters and bits are transmitted at a fixed rate with the transmitter and receiver synchronized. |
| system | An assembly of components united by some form of regulated interaction to function as an entity. |
| System Damage Voltage | Maximum voltage across a SiBar device at breakdown measured under a specified voltage rate of rise and current rate of rise. |
| System/3X (IBM) | The predecessor of the AS/400. |