Telecommunications terms starting with U

127 terms

U interface For basic-rate access in an Integrated Services Digital Network (ISDN) environment, a user-to-network interface reference point that is characterized by…
U reference point The conceptual reference point at the network side of the network termination 1 (NT1) in a particular ISDN access arrangement. [T1.615-1992] [T1.105-1988]
UDP User Datagram Protocol, the typical way to send datagrams over the Internet.
UHF Ultra High Frequency.
ULF Abbreviation for ultra low frequency. See electromagnetic spectrum.
Ultra High Frequency (UHF) Those radio frequencies exceeding 300 MHz
ultra low frequency (ULF) Frequencies from 300 Hz to 3000 Hz. See electromagnetic spectrum.
Ultraviolet (UV) Electromagnetic radiation of wavelength between the shortest visible violet (about 3,850 Angstroms) and soft x-rays (about 100 Angstroms).
ultrawideband See UWB.
unallowable character Synonym illegal character.
unassigned cell A cell identified by a standardized virtual path identifier (VPI) and virtual channel identifier (VCI) value, which has been generated and does not carry…
Unauthorized Disclosure An event involving the exposure of information to entities not authorized access to the information.
unavailability A expression of the degree to which a system, subsystem, or equipment is not operable and not in a committable state at the start of a mission, when the…
unbalanced line A transmission line, such as a coaxial cable, in which the magnitudes of the voltages on the two conductors are not equal with respect to ground.
unbalanced modulator A modulator in which the modulation factor is different for the alternate half-cycles of the carrier. Synonym asymmetrical modulator.
unbalanced wire circuit A circuit in which the two sides are inherently electrically dissimilar.
unbound mode Synonym radiation mode.
unbundling In the context of the FCC's Computer III Inquiry, the process of separating individual tariffed offerings and services that are associated with a specific…
unclassified Information that has not been determined pursuant to Executive Order (E.O.) 12958 or any predecessor order to require protection against unauthorized…
Underflow The movement of groundwater through the soil or a subsurface stratum, or under a structure; specifically, the water flowing beneath the bed of a stream…
underground cable A communication cable designed to be placed under the surface of the Earth in a duct system that isolates it from direct contact with the soil.
underground plant Cable and wire plant, together with closures appropriate for the application, that is placed below ground in structures such as conduit or ducts. [T1.
underlap In facsimile, a defect that occurs when the width of the scanning line is less than the scanning pitch.
undershoot An arc that does not extend far enough to intersect another arc. See also dangling arc.
undesired signal Any signal that tends to produce degradation in the operation of equipment or systems.
undetected error rate Deprecated synonym for undetected error ratio.
undetected error ratio The ratio of the number of bits, unit elements, characters, or blocks incorrectly received and undetected, to the total number of bits, unit elements…
undisturbed day A day during which neither sunspot activity nor ionospheric disturbance causes detectable interfere with radio communications.
unequipped indication A code placed in unequipped channels by originating equipment to indicate to path terminating equipment that the channel is intentionally unoccupied so…
unexpected frame A valid frame that cannot be processed. The frame itself is perfectly legitimate.
UNICOM station Synonym aeronautical advisory station.
unidirectional The condition where information flow is provided only in one direction. [T1.615-1992]
unidirectional channel Synonym one-way-only channel.
unidirectional operation Operation in which data are transmitted from a transmitter to a receiver in only one direction.
unidirectional path A path that logically connects a single path source with the associated path sink. [T1.231-1997]
uniform encoding An analog-to-digital conversion process in which, except for the highest and lowest quantization steps, all of the quantization subrange values are equal.
uniform linear array An antenna composed of a relatively large number of usually identical elements arranged in a single line or in a plane with uniform spacing and usually…
uniform quantizing Synonym uniform encoding.
uniform time scale A time scale made up of equal intervals.
uniform transmission line A transmission line that has distributed electrical properties, i.e., resistance, inductance, and capacitance per unit length, that are constant along the…
uniform-spectrum random noise See white noise.
unilateral control system Synonym unilateral synchronization system.
unilateral synchronization system A system of synchronization in which signals from a single location are used to synchronize clocks at one or more other locations.
unimode fiber Synonym single-mode optical fiber.
unintelligible crosstalk Crosstalk that consists of unintelligible signals, hence from which information cannot be derived.
unintentional interference See interference.
uninterruptible power supply (UPS) Backup power supply that is available when the electrical power fails or drops to unacceptable levels.
unipolar signal A two-state signal where one of the states is represented by voltage or current and the other state is represented by no voltage or current.
unique key Key held only by one crypto-equipment and its associated distribution center.
unit element In the representation of a character, a signal element that has a duration equal to the unit interval.
unit impulse A mathematical artifice consisting of an impulse of infinite amplitude and zero width, and having an area of unity.
unit interval In isochronous transmission, the longest interval of which the theoretical durations of the significant intervals of a signal are all whole multiples.
unit-distance code An unweighted code that changes at only one digit position when going from one number to the next in a consecutive sequence of numbers.
universal digital loop carrier A digital loop carrier (DLC) that uses a central office terminal (COT). [T1.216-1998]
Universal Personal Telecommunications (UPT) service A telecommunications service that provides personal mobility and service profile management.
universal personal telecommunications number Synonym UPT number.
universal service The concept of making basic local telephone service (and, in some cases, certain other telecommunications and information services) available at an…
Universal Time (UT) By international agreement, the local time at the prime meridian, which passes through Greenwich, England.
UNIX A software operating system.
unnumbered command In a data transmission, a command that does not contain sequence numbers in the control field.
unnumbered information (UI) frame A frame used to transfer unacknowledged information between two link layer entities. The format and encoding are the same as specified in Recommendation 0.
unnumbered response In data transmission, a response that does not contain sequence numbers in the control field.
unpark A function performed by the network if a call remains parked longer than a predesignated time limit, or if the parked party disconnects. [T1.653-1996]
unprivileged subject A subject without appropriate privileges to perform an operation [POSIX.6].
unstructured text Text for which no internal structure is defined and is unambiguously understood by a typical user [POSIX.6].
unsuccessful call Synonym unsuccessful call attempt.
unsuccessful call attempt A call attempt that does not result in the establishment of a connection. Synonym unsuccessful call.
untrusted process [A] Process that has not been evaluated or examined for adherence to the security policy.
unused character Synonym illegal character.
unwanted current With respect to telecommunications plant, any current that is not intentionally supplied from the central office or from telephone equipment. [After T1.
unwanted voltage With respect to telecommunications plant, any voltage that is not intentionally supplied from the central office or from telephone equipment. [After T1.
up-converter A device that translates frequencies from lower to higher frequencies.
update The process through which search crawls content and compiles an index of the content.
updating [In INFOSEC, an] automatic or manual cryptographic process that irreversibly modifies the state of a COMSEC key, equipment, device, or system. [INFOSEC-99]
Upgrade new or better version of some hardware or software.
uplink (U/L) 1. The portion of a communications link used for the transmission of signals from an Earth terminal to a satellite or to an airborne platform.
upright position Synonym erect position.
UPS Uninterruptible Power Source.
upstream The region extending in a 5' direction from a gene.
UPT See Universal Personal Telecommunications service.
UPT access code In universal personal telecommunications service, the code that UPT users may need to dial, when using some terminals and networks, to enter the UPT…
UPT access number (UPTAN) A number dialed by a UPT user to contact the service provider when using certain terminals and networks.
UPT database In universal personal telecommunications service, a repository for information, such as a service profile, that is related to a set of UPT customers and…
UPT environment In universal personal telecommunications service, the environment within which the UPT service facilities are offered, consisting of combinations of…
UPT indicator In universal personal telecommunications service, that portion (or portions) of the UPT number that identifies a call as a UPT call.
UPT number In universal personal telecommunications service, the number that uniquely identifies a UPT user and that is used to place a call to, or to forward a call…
UPT routing address In universal personal telecommunications service, the number used by the network to direct a call according to the user's UPT service profile.
UPT service profile In universal personal telecommunications service, a record that contains all information related to a UPT user, which information is required to provide…
UPT service profile management In universal personal telecommunications service, authorized access to and manipulation of the UPT service profile.
UPT subscriber In universal personal telecommunications service, a person who (or entity that) obtains a UPT service from a UPT service provider on behalf of one or more…
UPT user In universal personal telecommunications service, a person who (or entity that) has access to universal personal telecommunications (UPT) services and who…
UPT user group A specific set of universal personal telecommunications service users.
uptime The time during which a functional unit is fully operational.
URL (Uniform Resource Locator) The Internet address for a document, file, or other resource. It describes the protocol required to access the resource, the host where it can be found…
usable line length See available line.
usage Synonym occupancy.
useful line Synonym available line.
Usenet The collection of host computers and networks that exchange news articles organized by subject. [Exchange 5.5]
User A client with an email account.
user channel A communications channel allocated to the user for input of information such as data communication for use in maintenance activities and removing of…