signatoryThe entity that generates a digital signature on data. [After X9.31]
signatory authorityIn secure communications, an agreed entity (usually a third party) that issues signatory certificates to organizations participating in this authorization…
signatory certificateIn encryption, a certificate, issued by a signatory authority, that identifies the authorized signatories of an organization. [After X9.45]
significant conditionIn the modulation of a carrier, one of the values of the signal parameter chosen to represent information.
significant digitIn a representation of a number, a digit that is needed for a given purpose; in particular, a digit that must be kept to preserve a given accuracy or a…
significant instantIn a signal, any instant at which a significant condition of a signal begins or ends.
significant intervalThe time interval between two consecutive significant instants.
silence codeIn digital telephony, a code composed of a reserved binary number that is sent instead of an actual sound sample value from the CODEC when the incoming…
silent intervalAny portion of a ringing cycle during which the ringing signal is not being applied. [T1.401-1998]
silicon photodiodeA silicon-based PN- or PIN-junction photodiode. Note 1: Such photodiodes are useful for direct detection of optical wavelengths shorter than approximately…
simple authenticationAuthentication by means of simple password arrangements. [After X.509]
simple bufferingThe assigning of buffer storage for the duration of the execution of a computer program.
Simple Network Management Protocol (SNMP)A standard Internet protocol that facilitates communications between a system being managed and the management console or framework.
simple scanningIn facsimile transmission, scanning using only one spot at a time.
Simple Security ConditionA Bell- LaPadula security model rule allowing a subject read access to an object only if the security level of the subject dominates the security level of…
simple security property[The] Bell-La Padula security model rule allowing a subject read access to an object, only if the security level of the subject dominates the security…
simplex (SX) signalingSignaling in which two conductors are used for a single channel, and a center-tapped coil, or its equivalent, is used to split the signaling current…
simplex circuitA circuit that provides transmission in one direction only. 2. Deprecated definition: A circuit using ground return and affording communication in either…
simplex operationOperation in which transmission occurs in one and only one preassigned direction. Synonym one-way operation.
simplex protocolA communications protocol that is purely one-way, and where acknowledgments are not part of any application protocol.
simulateTo represent certain features of the behavior of a physical or abstract system by the behavior of another system.
SINADAbbreviation for signal-plus-noise-plus-distortion to noise-plus-distortion ratio. 1. The ratio of (a) total received power, i.e.
singingAn undesired self-sustained audio oscillation in a circuit. Note: Singing is usually caused by positive feedback, excessive gain, or unbalance of a hybrid…
singing marginThe difference in power levels between the singing point and the operating gain of a system or component.
singing pointThe threshold point at which additional gain in the system will cause self-oscillation.
Singing Return Loss (High & Low)The term "Singing Return Loss" denotes the frequency weighted measure of return loss at the edges of the voice band, where singing (instability) problems…
single classComprising or containing only one security class [CESG].
single class deviceA device which can only be used to process information of a single security class at a time [CESG]
single point keying[A] means of distributing key to multiple, local crypto-equipment or devices from a single fill point. [INFOSEC-99]
single point of controlA control relationship where the same phase or aspect of a call/service attempt is influenced by one and only one service control function. [T1.667-1999]
single-ended service featureA feature, e.g., call/service attempt manipulation, that applies to only one of the parties that may be involved on a call/service attempt. [T1.667-1999]
single-ended synchronizationSynchronization between two locations, in which phase error signals used to control the clock at one location are derived by comparing the phase of the…
single-frequency (SF) signalingIn telephony, signaling in which dial pulses or supervisory signals are conveyed by a single voice-frequency tone in each direction.
single-frequency interferenceInterference caused by a single-frequency source. Note 1: An example of single-frequency interference is interference in a transmission channel induced by…
single-harmonic distortionOf a fundamental frequency, the ratio of the power of a specified harmonic to the power of the fundamental frequency.
Single-Level DeviceA device that is used to process data of a single security level at any one time.
single-polarized antennaAn antenna that radiates or receives radio waves with a specific polarization. Note: For a singly polarized antenna, the desired sense of polarization is…
single-sideband (SSB) equipment reference levelThe power of one of two equal tones that, when used together to modulate a transmitter, cause it to develop its full rated peak power output.
single-tone interferenceAn undesired discrete frequency appearing in a transmission channel. Note: The single-tone interference frequency is the frequency that appears in the…
SinkAny process, activity, or mechanism which removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere.
SiteIn archeology, any location of past human activity.
skewIn parallel transmission, the difference in arrival time of bits transmitted at the same time. 2.
skew rayIn a multimode optical fiber, a bound ray that travels in a helical path along the fiber and thus (a) is not parallel to the fiber axis, (b) does not lie…
SkimmingThe act of obtaining data from an unknowing end user who is not willingly submitting the sample at that time.
skin effectThe tendency of alternating current to flow near the surface of a conductor, thereby restricting the current to a small part of the total cross-sectional…
SKIPA non-digging bucket or tray that hoists material
skip distanceAt a given azimuth, the minimum distance between the transmitting station and the closest point of return to the Earth of a transmitted wave reflected…
skip zoneAn annular region within the transmission range of an antenna, within which signals from the transmitter are not received.
sky waveA radio wave that travels upward from the antenna. Note: A sky wave may be reflected to Earth by the ionosphere.
slab-dielectric waveguideAn electromagnetic waveguide (a) that consists solely of dielectric materials, (b) in which the dielectric propagation medium has a rectangular cross…
slammingThe action that occurs when a customer's long-distance telephone service (carrier selection) is switched from one long distance company to another without…
slant rangeThe line-of-sight distance between two points, not at the same level relative to a specific datum.
slave clockA clock that is coordinated with a master clock. Note 1: Slave clock coordination is typically achieved by phase-locking the slave clock output signal to…
slave stationIn a data network, a station that is selected and controlled by a master station.
slewingRotating a directional antenna or transducer rapidly about one or more axes. 2. Changing the frequency or pulse repetition rate of a signal source. 3.
sliding windowA variable-duration window that allows a sender to transmit a specified number of data units before an acknowledgement is received or before a specified…
slopeAn inclined surface usually defined by the ratio of the horizontal distance to the vertical distance, i.e. 2:1 (2 horizontal units to 1 vertical unit).
slope equalizerA device or circuit used to achieve a specified slope in a metallic transmission line.
slope-keypoint compactionData compaction accomplished by stating (a) a specific keypoint of departure, (b) a direction or slope of departure, (c) the maximum deviation from a…
slotA fishing size limit where the angler may keep fish shorter than a minimum length but longer than an upper length limit.
slot antennaA radiating element formed by a slot in a conducting surface or in the wall of a waveguide.
slot timeIn networks using carrier sense multiple access with collision detection (CSMA/CD), the length of time that a transmitting station waits before attempting…
slotted-ring networkA ring network that allows unidirectional data transmission between data stations by transferring data in predefined slots in the transmission stream over…
SMDRAbbreviation for station message-detail recording.
smearingIn video displays, a localized distortion over a sub-region of the image, characterized by reduced sharpness of edges and spatial detail.
SMILAcronym for synchronized multimedia integration language. A protocol for downloading digitized streams or audio/video data files in the absence of a…
smooth EarthIdealized surfaces, such as water surfaces or very level terrain, having radio horizons that are not formed by prominent ridges or mountains but are…
SMS/800 Help DeskThe organization that administers the SMS/800 system for the centralized management of Toll Free numbers.
SMTPSimple Mail Transfer Protocol (computer term).
SNAAbbreviation for systems network architecture. A proprietary communications architecture.
sneak currentIn a communications circuit, an anomalous current that presents no immediate danger, but may cause improper operation or damage.
sneak current protectionApplication of a protective device that is intended to limit currents that are too small to operate fuse links, stub cables, or the fuse of a fused…
Snell's lawA law of geometric optics that defines the amount of bending that takes place when a light ray strikes a refractive boundary, e.g.
SnifferThe name of the filter program used by the Infoseek search engine to prevent spamdexing.
SNMPSimple Network Management Protocol. A standard Internet protocol that facilitates communications between a system being managed and the management console…
SnowPrecipitation that consists of frozen flakes formed when water vapor accumulates on ice crystals, going directly to the ice phase.