For basic-rate access in an Integrated Services Digital Network (ISDN) environment, a user-to-network interface reference point that is characterized by the use of a 2-wire-loop transmission system that (a) conveys information between the 4-wire user-to-network interface, i.e., the S/T reference point, and the local exchange, (b) is located in the servicing central office, and (c) is not as distance sensitive… (Read More →)

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]

Universal Description, Discovery, and Integration

User Datagram Protocol

1. User Equipment,
2. User Element.

Abbreviation for ultra high frequency. See electromagnetic spectrum.

User Interface

Universal Integrated Circuit Card

unsigned integer, most significant bit first

Abbreviation for ultra low frequency. See electromagnetic spectrum.

Frequencies from 300 MHz to 3000 MHz. See electromagnetic spectrum.

Frequencies from 300 Hz to 3000 Hz. See electromagnetic spectrum.

The portion of the electromagnetic spectrum in which the longest wavelength is just below the visible spectrum, extending from approximately 4 nm to approximately 400 nm.
Note: Some authorities place the lower limit of uv at values between 1 and 40 nm, 1 nm being the upper wavelength limit of x-rays. The 400-nm limit is the lowest visible wavelength, i.e.,… (Read More →)

See UWB.

Unified Modeling Language

Universal Mobile Telecommunication System

Synonym illegal character.

A cell identified by a standardized virtual path identifier (VPI) and virtual channel identifier (VCI) value, which has been generated and does not carry information from an application using the ATM Layer service. [T1.627-1993]

Exposure of information to individuals not authorized to receive it. [INFOSEC-99]

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 mission is called for at an unknown, i.e., random, time.
Note 1: The conditions determining operability and committability must be specified.
Note 2: Expressed mathematically, unavailability is 1 minus the availability.… (Read More →)

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.

A modulator in which the modulation factor is different for the alternate half-cycles of the carrier. Synonym asymmetrical modulator.

A circuit in which the two sides are inherently electrically dissimilar.

Synonym radiation mode.

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 element in the CEI or ONA tariff from other tariffed basic service offerings. [After para.158, FCC Report and Order, June 16,
198
6. ]

Information that has not been determined pursuant to Executive Order (E. O. ) 12958 or any predecessor order to require protection against unauthorized disclosure and that is not designated as classified. [INFOSEC-99]

In computing, a condition occurring when a machine calculation produces a non-zero result that is smaller than the smallest non-zero quantity that the machine's storage unit is capable of storing or representing.

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.

Cable and wire plant, together with closures appropriate for the application, that is placed below ground in structures such as conduit or ducts. [T1.316-1997]

In facsimile, a defect that occurs when the width of the scanning line is less than the scanning pitch.

See overshoot.

Any signal that tends to produce degradation in the operation of equipment or systems.

Deprecated synonym for 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, characters, or blocks sent. Synonyms residual error rate, undetected error rate [deprecated].

A day during which neither sunspot activity nor ionospheric disturbance causes detectable interfere with radio communications.

A code placed in unequipped channels by originating equipment to indicate to path terminating equipment that the channel is intentionally unoccupied so that alarms can be inhibited. [T1.105-1988]

A valid frame that cannot be processed. The frame itself is perfectly legitimate. Its unexpected character is defined by two conditions: the specific type of frame and the state of the receiver. [T1.218-1991] The layer-2 protocol states define the proper sequence in which frames are expected to occur. The receiver will compare received frames with its own protocol state to… (Read More →)

User-to-Network Interface

Synonym aeronautical advisory station.

Uniform Interface to Computing Resources

The condition where information flow is provided only in one direction. [T1.615-1992]

Synonym one-way-only channel.

Operation in which data are transmitted from a transmitter to a receiver in only one direction.

A path that logically connects a single path source with the associated path sink. [T1.231-1997]

An analog-to-digital conversion process in which, except for the highest and lowest quantization steps, all of the quantization subrange values are equal. Synonym uniform quantizing.

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 with a uniform feed system.

Synonym uniform encoding.

A time scale made up of equal intervals.

A transmission line that has distributed electrical properties, i.e., resistance, inductance, and capacitance per unit length, that are constant along the line, and in which the voltage-to-current ratio does not vary with distance along the line, if the line is terminated in its characteristic impedance.
Note 1: Examples of uniform transmission lines are coaxial cables, twisted pairs, and single wires… (Read More →)

See white noise.

Synonym 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. Synonym unilateral control system.

Synonym single-mode optical fiber.

Crosstalk that consists of unintelligible signals, hence from which information cannot be derived.

See interference.

A device that is inserted between a primary power source, such as a commercial utility, and the primary power input of equipment to be protected, e.g., a computer system, for the purpose of eliminating the effects of transient anomalies or temporary outages.
Note 1: An UPS consists of an inverter, usually electronic, that is powered by a battery that is… (Read More →)

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.
Note: The current flow can be in either direction.

Key held only by one crypto-equipment and its associated distribution center.

In the representation of a character, a signal element that has a duration equal to the unit interval.

A mathematical artifice consisting of an impulse of infinite amplitude and zero width, and having an area of unity.
Note: The unit impulse is useful for the mathematical expression of the impulse response, i.e., the transfer function, of a device. Synonym Dirac delta function.

In isochronous transmission, the longest interval of which the theoretical durations of the significant intervals of a signal are all whole multiples.

An unweighted code that changes at only one digit position when going from one number to the next in a consecutive sequence of numbers.
Note 1: Use of one of the many unit-distance codes can minimize errors at symbol transition points when converting analog quantities into digital quantities.
Note 2: An example of a unit-distance code is the Gray code.… (Read More →)

A digital loop carrier (DLC) that uses a central office terminal (COT). [T1.216-1998]

A telecommunications service that provides personal mobility and service profile management.
Note 1: UPT service involves the network capability of identifying uniquely a UPT user by means of a UPT number.
Note 2: The general principles of UPT are given in ITU-T Recommendation F.85
0.
Note 3: UPT and PCS are sometimes mistakenly assumed to be the same service concept.… (Read More →)

Synonym UPT number.

The concept of making basic local telephone service (and, in some cases, certain other telecommunications and information services) available at an affordable price to all people within a country or specified jurisdictional area.

1. The basis for coordinated dissemination of time signals, counted from 0000 at midnight.
2. In celestial navigation applications, the time which gives the exact rotational orientation of the Earth obtained from UTC by applying increments determined by the U. S. Naval Observatory.
3. A measure of time that conforms, within a close approximation, to the mean diurnal rotation of… (Read More →)

TM: A portable, multiuser, time-shared operating system that supports process scheduling, job control, and a programmable user interface.
Note 1: There are many proprietary operating systems that are based on UNIXTM and are commonly referred to as UNIXTM, but are not necessarily interoperable.
Note 2: Most UNIXTM-based operating systems are POSIX compliant.

In a data transmission, a command that does not contain sequence numbers in the control field.

A frame used to transfer unacknowledged information between two link layer entities. The format and encoding are the same as specified in Recommendation
0. 921/
1.
44
1. The CRC (cyclic redundancy check) is derived over the entire frame. [T1.509-1995]

In data transmission, a response that does not contain sequence numbers in the control field.

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]

A subject without appropriate privileges to perform an operation [POSIX.6].

Text for which no internal structure is defined and is unambiguously understood by a typical user [POSIX.6].

Synonym unsuccessful call attempt.

A call attempt that does not result in the establishment of a connection. Synonym unsuccessful call.

[A] Process that has not been evaluated or examined for adherence to the security policy. It may include incorrect or malicious code that attempts to circumvent the security mechanisms. [INFOSEC-99]

Synonym illegal character.

With respect to telecommunications plant, any current that is not intentionally supplied from the central office or from telephone equipment. [After T1.316-1997]

With respect to telecommunications plant, any voltage that is not intentionally supplied from the central office or from telephone equipment. [After T1.316-1997]

Unified Ordering Model

A device that translates frequencies from lower to higher frequencies.

Universal Powerline Bus

The regeneration of a display to show current status, based on changes to the previously displayed data.
Note: An update can be accomplished upon user request or by automatic means.

[In INFOSEC, an] automatic or manual cryptographic process that irreversibly modifies the state of a COMSEC key, equipment, device, or system. [INFOSEC-99]

To change a MAC label or Information Label to a label that dominates the current label but is not equivalent to the current label [POSIX.6].

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.
Note: An uplink is the converse of a downlink.
2. Pertaining to data transmission from a data station to the headend.

Universal Plug and Play

Synonym erect position.

Acronym for uninterruptible power supply.

User Profile Server Function

1. The direction opposite the data flow.
2. With respect to the flow of data in a communications path: at a specified point, the direction toward which data are received earlier than at the specified point.

See Universal Personal Telecommunications service.

In universal personal telecommunications service, the code that UPT users may need to dial, when using some terminals and networks, to enter the UPT environment before executing any UPT procedures.

A number dialed by a UPT user to contact the service provider when using certain terminals and networks. In order to achieve its purpose, the UPTAN must contain information that can be used (a) to route the call to the user's service provider and (b) to specify the service profile. The UPTAN should be an E.164 number. [After T
1.… (Read More →)

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 users.

In universal personal telecommunications service, the environment within which the UPT service facilities are offered, consisting of combinations of networks and UPT service control facilities that, when combined, enable UPT users to make use of telecommunication services offered by these networks.
Note: To the UPT user, the UPT environment appears as a single global network that provides personal mobility. However,… (Read More →)

In universal personal telecommunications service, that portion (or portions) of the UPT number that identifies a call as a UPT call.

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 to, that user.
Note: A user may have multiple UPT numbers, e.g., a business UPT number for business calls and a private UPT number for private calls. In the case of multiple numbers,… (Read More →)

In universal personal telecommunications service, the number used by the network to direct a call according to the user's 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 that user with UPT service such as subscriptions to basic and supplementing services and call-routing preferences.
Note: Each UPT service profile is associated with a single UPT number. Synonym service profile.

In universal personal telecommunications service, authorized access to and manipulation of the UPT service profile.
Note: UPT service profile management can be performed by the UPT user, by the UPT customer (subscriber), or by the UPT service provider. Synonym service profile management.

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 users.

In universal personal telecommunications service, a person who (or entity that) has access to universal personal telecommunications (UPT) services and who has been assigned a UPT number.

A specific set of universal personal telecommunications service users.

The time during which a functional unit is fully operational.

Uniform Resource Identifier

Uniform Resource Locator

A character string describing the location and access method of a resource on the Internet.
Note: For example, the URL http://www. ycom. com describes the type of access method being used (http) and the server location which hosts the Web site (www. ycom. com).

Uniform Resource Name

See available line.

Synonym occupancy.

Universal Serial Bus

Synonym available line.

The name of a set of computers and networks used for creating, forwarding, or displaying some computer conferences. [2382-pt.35]

1. A person, organization, or other entity (including a computer or computer system), that employs the services provided by a telecommunication system, or by an information processing system, for transfer of information.
Note: A user functions as a source or final destination of user information, or both. Synonym subscriber.
2. [Insecurity, a] person or process authorized access to an IS… (Read More →)

An entity that carries out specific functions on behalf of its owner or user. Such functions usually entail requesting some service or responding to a request for service. When requesting service, the User Agent acts as a User Agent Client (UAC), and when responding to a request for service, it acts like a User Agent Server (UAS). For example, a… (Read More →)

A communications channel allocated to the user for input of information such as data communication for use in maintenance activities and removing of alarms external to the span equipment in a proprietary fashion. [After T1.105-1988]

In the Internet Protocol suite, a standard, low-overhead, connectionless, host-to-host protocol that is used over packet-switched computer communications networks, and that allows an application program on one computer to send a datagram to an application program on another computer.
Note: The main difference between UDP and TCP is that UDP provides connectionless service, whereas TCP does not.

1. A character string or pattern that is used by a data processing system to identify a user. [2382-pt.8]
2. [A] unique symbol or character string used by an information system (IS) to identify a specific user. [INFOSEC-99] Synonym user identification.

1. A character string which uniquely identifies a user to a system [CESG]. See also: Password.
2. See user ID.

A standard device or functionality providing secure procedures in support of registration, authentication, and privacy for wireless access to PCS, and which may also be used to facilitate other services (e.g., UPT, banking). [After T
1. Rpt44-1995]

Information transferred across the functional interface between a source user and a telecommunications system for delivery to a destination user.
Note: In telecommunications systems, user information includes user overhead information.

A bit transferred from a source user to a telecommunications system for delivery to a destination user.
Note 1: User information bits do not include the overhead bits originated by, or having their primary functional effect within, the telecommunications system.
Note 2: User information bits are encoded to form channel bits.

A block that contains at least one user information bit.

The convergence of a full range of user interface types, including fixed terminals, mobile handsets or other user devices and interfaces.

Synonym loop.

See overhead information.

A functional part of the common channel signaling system that transfers signaling messages via the message transfer part. Different types of user parts exist (e.g., for telephone and data services), each of which is specified to a particular use of the signaling system. [T1.110-1987]

Protection of information about users from uninvited and possibly illegal access. [T
1. Rpt34-1994]

1. The profile that includes the service profile and contains all the data associated with the user, e.g., incoming call handling information, selection of service provider/service area coverage, service subscriptions, service parameters, etc. [T
1. Rpt34-1994]
2. A description of a user, typically used for access control. [2382-pt.8]
Note: A user profile may include data such as user ID, user… (Read More →)

[A] person authorized by an organization to order COMSEC keying material and interface with the keying system; providing information to key users and ensuring the correct type of key is ordered. [INFOSEC-99]

Synonym class of service.

1. The point of demarcation between a common carrier's facilities and customer's installation, which demarcation establishes both the technical interface and the division of operational responsibility. In this context, "customer" refers to the end-user. [J. Beaty FAA]
2. The term used to refer to the network interface (NI) as well as to interfaces within the customer installation (CI). [T1.640-1996]

An ISDN number, supplied completely or partially by the calling user or the redirecting user, that is associated with the calling user or the redirecting user. The UPN may also be accompanied by a subaddress. [T1.625-1993]

Universal Subscriber Identity Module

United States Naval Observatory

Abbreviation for Universal Time.

Abbreviation for Coordinated Universal Time.

Coordinated Universal Time (UTC), as kept by the "i" laboratory, where i is any laboratory cooperating in the determination of UTC.
Note: In the United States, the official UTC is kept by the U. S. Naval Observatory and is referred to as UTC (USNO).

Synonymnonoperational load.

A computer program that is in general support of the operations and processes of a computer.
Note: Examples of utility programs include diagnostic programs, trace programs, input routines, and programs used to perform routine tasks, i.e., perform everyday tasks, such as copying data from one storage location to another. Synonyms service program, service routine, tool, utility routine.

Synonym utility program.

The utilization level in a given geographic area (NPA or rate center) is calculated by dividing all assigned numbers (numerator) by total numbering resources assigned to that carrier in the appropriate geographic region (denominator), and multiplying the result by
10
0.  Numbering resources activated in the LERG™ Routing Guide (within the preceding 90 calendar days of reporting utilization levels may… (Read More →)

Universal Terrestrial Radio Access

A standardized, MIME-compliant method of decoding uuencoded e-mail messages by decoding binary data that was conveyed as a character string over a character-only channel. [After 2382-pt.35]

1. A standardized, MIME-compliant method of encoding e-mail and other electronically transferred messages to provide a minimum level of security through encryption.
2. The name of a program for conveying binary data as a character string over a character-only channel. [2382-pt.35]

Abbreviation for ultraviolet.

1. Abbreviation for ultrawideband.
1. Referring to any radio or wireless device where the occupied bandwidth is greater than 25% of the center frequency or greater than
1. 5 GHz.
2. A radio or wireless system that uses narrow pulses (on the order of 1 to 10 nanoseconds), also called carrierless or impulse systems, for communications and sensing (short-range radar).… (Read More →)